Search

This paper contributes to the discussion on climate change impacts, livelihood diversification, and deagrarianization in arid and semi-arid regions. Using the semi-arid region of Guinea as a case study, this paper is the first to discuss the primary factors driving smallholder farmers into artisanal and small-scale mining (ASM) in arid and semi-arid regions. Drawing on in-depth interviews and root-cause analysis, we find that increasing climate change impacts 'force' smallholder farmers to switch into artisanal gold mining. Smallholder farming in semi-arid Guinea is largely rainfed and erratic rainfall and increasing temperatures have affected crop production and farmers' income, driving many smallholder farmers into artisanal gold mining to have a more sustainable income. While artisanal gold mining has improved smallholder farmers' socioeconomic conditions, the agriculture exodus has significantly affected crop production, food prices, and rural agriculture labor dynamics. Agroecological, financial, and technical support could improve the adaptive capacity of climate impacted smallholder farmers in arid and semi-arid regions. • Agrarian communities are now transforming into artisanal mining communities due primarily to climate change. • Dry farmlands, low farm productivity, and low farm income are secondary factors that drive farmers into the ASM economy. • Farmers converted to miners to cope with climate change impacts and not necessarily to 'get rich quick'. • Smallholder farmers in semi-arid Guinea lack access to climate adaptive strategies. • Livelihood diversification from farming to ASM affects rural socioeconomics and threatens food security. [ABSTRACT FROM AUTHOR]

• Evaluating the Water Resources Constraint Intensity(WRCI) from the Perspective of High-quality Development. • An Analytic Hierarchy Process (AHP) model reformed by entropy technology and a multi objective fuzzy membership function were employed for indicator aggregation. • The spatiotemporal changes and correlation of UQDI, WRI, and WRCI in 78 prefecture level cities in the Yellow River Basin during 2011–2020 were analyzed. Promoting the high-quality development of urbanization is a crucial way to achieve sustainable development goals. Water resources are a rigid constraint for such development. However, There is still room for improvement in the research on the spatio-temporal pattern and key driving factors of high-quality urbanization development under the constraint of water resources. Aiming at the problem that the high-quality development of urbanization in the Yellow River Basin (YRB) is facing water resources constraints, this paper discussed the spatial–temporal pattern and key drivers of the high-quality development of urbanization in the YRB under water resource constraints by using the Analytic Hierarchy Process model reformed by entropy technology, multi-objective fuzzy membership function, spatial autocorrelation analysis and obstacle model. The results revealed that, first, we found the High-Quality Urbanization Development Index (UQDI) exhibited steady growth, while both the Water Resources Index (WRI) and the Water Resources Constraint Intensity (WRCI) initially increased and then decreased during the study period. Second, the UQDI displayed a dual-core pattern, with the Shandong Peninsula urban agglomeration and the Central Plains urban agglomeration serving as the cores. WRI exhibited relatively stable spatial distribution, with the southeast region outperforming the northwest. WRCI also demonstrated a relatively stable spatial distribution, resulting in two weak-constraint areas, represented by Shandong and Henan, and a strong-constraint area centered around Ningxia. Third, the UQDI, WRI, and WRCI exhibited spatial interdependence. The spatial interdependence of UQDI and WRI increased, while that of WRCI decreased during the study period. The three indexes also displayed a clear pattern of local clustering in space. Two low-value aggregation areas, namely Shandong and Henan, and a high-value aggregation area located in Ningxia, emerged during the study period. Last, the WRCI was primarily influenced by the fundamental conditions of water resources. The main influencing factors included per capita water resources, mean annual precipitation, total water resources, water resources modulus, and the total amount of foreign investment utilization. In light of the research findings, the paper proposes policy recommendations for promoting high-quality urbanization development in the YRB. This study provides decision-making guidance for countries and regions in arid areas to solve the water resources constraints on the high-quality development of urbanization. [ABSTRACT FROM AUTHOR]

This paper explores how pastoralists collectively manage resources in contexts of high environmental variability in the drylands of southern Tunisia. The khlata , the practice of pooling herds, allows for livestock owners to manage scarce resources in environments characterized by non-equilibrium dynamics. This institution legitimizes access to a wider range of pasture land thus tracking patchy rainfall distribution, and allows for the sharing of herding labour and so allows for "absence" in pastoral production, thus enabling human mobility. The khlata , recasts conceptualizations of tenure and labour in ways that subvert neoliberal models of production, and adapt to changing political economic conditions. Such collective herding practices can be likened to "high-reliability" management ideas that accommodate the social and networked dimensions of land-use in drylands, where coordination and connectivity through institutions becomes crucial. The theoretical approach includes pastoral perspectives on tenure, where rules are not well defined and membership is fluid, contributing to a different take on conventional common-property debates and neoliberal views on property, and indeed institutions. When pastoral production is framed as a high-reliability system, the objective of maintaining security and at the same time flexibility in land tenure is emphasised: livestock owners make use of a wide range of scale-dependent resources, whether public, private, or common property. Land-use policy should therefore focus not on rules and regulations but how to support institutions that maintain a highly-reliable system within contexts of fuzzy tenure regimes. Land-use policy should therefore focus on coordinating connectivity through collective arrangements by prioritizing the "informal" and adaptive nature of institutions such as the khlata , rather than focusing on their formalization. Overall, the paper shows how the khlata redefines access to land and labour in ways that create additional options for pastoralists to adapt to changing political economic conditions in southern Tunisia. • The collective management of pastoral resources is key in non-equilibrium ecologies, such as drylands. • Collective herding arrangements, like the khlata , create options for pastoralists by redefining access to land. • Collective practices evolve to meet changing conditions by maintaining flexible and secure access to resources, including labour. • Pastoral perspectives contribute to a different take on conventional common-property debates. • Land-use policy should prioritize the "informal" and adaptive nature of pastoral institutions. [ABSTRACT FROM AUTHOR]

To design policies for sustainable irrigation planning, public decision-makers need knowledge about the potential environmental impacts of irrigated farming systems. In a previous paper, we proposed to couple Life Cycle Assessment (LCA) and Agrarian System Diagnosis (ASD) to build the Life Cycle Inventory (LCI) of a farming region in a context of data scarcity and farming system diversity. This method was applied to the semi-arid irrigated plain of Kairouan (Tunisia). The aim of the present paper is to demonstrate how this new ASD-based LCA method is used to conduct the impact assessment of this farming region, under current conditions and for two prospective scenarios. Two functional units (FU) were used: the area and the gross product generated. Life Cycle Impact Assessment (LCIA) was conducted based on a multilevel process, by converting LCI data collected for each cropping/ livestock system into LCIA outputs, which were then consolidated at the farming system (FS) and at the regional scales. Two scenarios, based on observed trends, were assessed: the "agrarian" scenario (driven by a shift from family to corporate farming) and the "hydrological" scenario (driven by a water table drawdown). Environmental hotspots were identified at each scale: the most impactful FS was the "mixed family farming" (intermediate access to water), because of its large share of land at the regional scale (45%). In this FS, the most harmful cropping system was input-intensive olive groves intercropped with a melon-pepper/ cereal/ tomato rotation, in which most impacts (35%) were attributable to the input-intensive "melon" crop, and more particularly to "manufacture and transport of fertilizer", including farmyard manure. Globally, the most harmful processes were water and fertilizer use (fertilizer manufacturing and transportation). This downscaling is very useful to inform public policies on the most harmful productions. The impacts in human, ecosystem and resource endpoints increased by 11%, 2%, 9% and 23%, 27% and 40%, for the agrarian and hydrological scenarios respectively. These results show that observed trends in farming practices evolution (more irrigation) should be stopped. Our method has three main strengths: i) inter-farms synergies are accounted for in the LCIA, which is essential to promote circularity; ii) thanks to the innovative and multilevel approach, the origins of environmental hotspots can be investigated and later mitigated by future policies; iii) ASD helps to design sustainable scenarios by identifying current trends and regional thresholds (resources, pollution and workforce) that cannot be overcome. [Display omitted] • Multilevel Life Cycle Impact Assessment (LCIA) was conducted in a semi-arid irrigated plain (Tunisia). • Agrarian System Diagnosis and Life Cycle Assessment methods were coupled. • Environmental hotspots are modeled from the plot /herd, up to the regional scale. • Main impacts are caused by water depletion, fertilizer manufacturing and manure transportation. • Environmental impacts may increase by 40% in trend evolution scenarios (watertable depletion and less familial farming). [ABSTRACT FROM AUTHOR]

• The oasis cooling effect was investigated within 12 scenarios in three seasons. • The human thermal comfort was evaluated based on the PET index in arid climates. • A neutral range can be ensured in well-defined spatial and microclimatic aspects. • Palm tree grids of 10 and 12 m are the optimal scenarios for the neutral range. • The neutral range is mainly affected by T mrt with a rate of 53%. With climate change and the recurring heat waves in arid lands, human well-being and activities in oasis settlements can be critical subjects for the ongoing years. This paper introduces a methodological approach to investigate the potential passive cooling effect inside the oasis palm groves, their spatial characteristics, and microclimatic thresholds. Based on the Physiological Equivalent Temperature (PET) index, the paper evaluates oasis palm groves' ability to ensure a neutral human outdoor thermal comfort zone. The research aims to determine guidance of an optimal and nearly optimal thermal comfort threshold based on a series of parametric scenarios of oasis configurations. The study provides a cross of 12 ideal oasis scenarios. The paper evaluates the oasis cooling effect and thermal comfort and recommends aligning urban planning with thermal thresholds. Results reveal that PET neutral zone can be assured into ranges of 29°C to 37°C, 19°C to 20°C, 55% to 58%, and 1m/s to 2m/s of mean radiant temperature, air temperature, relative humidity and air velocity , respectively. The results refer policymakers and urban planners to invest in the passive cooling effect of the oasis palm grove in future urban design strategies to maintain the maximum neutral comfort hours during heat waves. [ABSTRACT FROM AUTHOR]

• This review is directed to evaluate the scope and limitations of floating solar stills and floating solar-driven membranes. • Over 35 papers were reviewed to explain the concept of floating solar stills, solar-driven membranes, and related concepts. • Floating solar stills and solar-driven membranes are effective in remote or rural coastal areas. • Floating solar stills and floating solar-driven membranes have a future potential as small-scale desalination technology. • Floating solar stills and solar-driven membranes can convert 90% of solar into vapor using an interfacial heating evaporator. For life to exist on earth, there must be water. Freshwater resources are in short supply due to industrialization and the world's rapid population expansion. Growing water shortage argues that using passive solar stills is the best and most practical solution in the world's arid and semi-arid regions. For applications in distant or rural coastal areas, floating solar stills are an appropriate technique. To provide accessibility to a wider population, the gadget should be constructed using inexpensive materials that are easily accessible nearby. However, the low-cost materials typically do not have the optimum physical characteristics, which reduces the overall performance of solar stills. This study intends to deliver a comprehensive review that summarizes recent research developments and gives a rundown of experimental, numerical, and experimental and numerical studies on floating solar stills and floating solar-driven membranes. This article also looks at a few more setups, researched parameters, and result-finding issues. Research on floating solar is currently ongoing, and recommendations for further research projects have been made in light of the study's findings. [ABSTRACT FROM AUTHOR]

Sedimentation in front of a dam is the main obstacle against reservoir sustainability. Due to the limited availability of suitable new dam sites, the ramifications of inefficient sediment management are associated with socio-economic concerns and environmental issues. Most of the existing sediment management techniques are unfavorable for arid and semi-arid regions due to their impacts on available water storage and power generation. Therefore, pressure flushing is an economical desilting method as it releases little water through the bottom outlet. However, one of the main disadvantages of pressurized flushing is limited sediment removal near the bottom outlet. In this paper, the impacts of a dendritic, bottomless, and extended (DBE) structure were investigated to develop the scour cone to a broader area. Several experiments were carried out with four different diameters (125, 160, 200, and 250 mm), four different lengths (30, 50, 80, and 110 cm), and three discharge rates (12.5, 15, and 18 L/s), to identify the dimensions of the extended structure with the most efficient operation. The results indicated that the DBE structure with a length dimensionless index of L DBE / D o = 10 , a diameter dimensionless index of D DBE / D o = 1.14 , and an outflow discharge dimensionless index of Fr o = 1.82 , yielded a 36.55-fold increase in the sediment flushing cone dimensions and sediment removal efficiency compared to a reference test. Finally, a dimensionless equation is presented for calculating the sediment flushing cone dimensions, according to a statistical analysis of the results. Two diagrams are provided to illustrate the interrelationship between the distance limits of scour, length, and diameter of the structure and outlet discharges. [ABSTRACT FROM AUTHOR]

Groundwater banking has been used for demand-oriented management of groundwater resources in semi-arid and arid regions. This paper aims to propose a new framework for seasonal groundwater banking. In this framework, crop production functions are used to estimate users' bid packages representing the price of each unit volume of water in each auction period. The bid packages, along with users' water rights, are considered inputs of an optimization model, which maximizes the profit of users participating in the groundwater bank. The main outputs of the optimization model are the volumes of exchange and storage of water, as well as the water price in the auction periods. The efficiency of the proposed framework has been evaluated by applying it to the Nough region in the Rafsanjan Plain, central Iran. An existing plan for inter-basin water transfer to this region is also considered in the water banking framework. The results illustrate that the total annual profit of all users after the establishment of the bank compared to the status quo has increased up to 43.8 %. The profit of the water-recipient basin has also increased more than 4 times compared to the existing condition. In addition, water banking with a water transfer system increases the economic productivity of water and crop production by 37.32 % and 22.41 %, respectively. • Water banking is a demand-management mechanism for storing and exchanging water. • A new mechanism is presented for seasonal water banking in agricultural regions. • In the bank, water price is calculated based on the seasonal bid-packages. • The seasonal bid-packages are estimated using production functions of plants. • The efficiency of the methodology is shown through a real-world case study. [ABSTRACT FROM AUTHOR]

Hainan Island in southern China is situated within the Indo-Burma biodiversity hotspot, and has attracted the attention of evolutionary biologists, geologists, and biogeographers. However, the palaeogeography of Hainan Island and its relationship with mainland China remains contested. In this paper, we report RAD-seq data for Engelhardia roxburghiana populations from Hainan Island and adjacent mainland areas to identify genetic diversity, structure, divergence time, and demographic dynamics over geologic time. Findings were assessed using climate model data to constrain suitable distribution areas. Results indicate that E. roxburghiana dispersed from the Chinese mainland to Hainan Island via a hypothetical land bridge during the late Eocene so that the drift of Hainan Island was impossible. We cast doubt on the hypothesis that Hainan Island was connected to Vietnam and Guangxi at this time. We emphasize that higher genetic diversity in the Yunnan-Guizhou Plateau and Chiang-nan regions is the result of mixed populations or the existence of refugia, and lower genetic diversity in the Indochina Peninsula is due to a historical bottleneck. From the late Eocene to Oligocene, the arid belt that dominated East Asia retreated, facilitating the expansion of E. roxburghiana from the Indochina Peninsula to southern China. The main diversification of E. roxburghiana occurred in the Miocene following the strengthening precipitation within the East Asian Summer Monsoon. Climatic oscillations during the Quaternary led to the contraction of E. roxburghiana in the Indochina Peninsula, with expansion after Last Glacial Period (LGP; 119 to 11.7 ka). Southern China has served as a refugium and continues to do so in the future. In summary, our study elucidates the evolutionary trajectory of E. roxburghiana through large-scale sampling, providing insights into the palaeogeography of Hainan Island and itsbiogeographic relationships with adjacent mainlands. • A land bridge facilitated the spread of Engelhardia roxburghiana from Chiang-nan to Hainan Island in the late Eocene. • Engelhardia roxburghiana 's evolution follows Asian climate shifts, spreading north as arid zones retreated. • The diversification of Engelhardia roxburghiana occurred concurrently with intensified EASM precipitation during the Miocene. • Southern China was the refugium during the Quaternary glaciations and continues to do so in the future. [ABSTRACT FROM AUTHOR]

Long-term rates of escarpment retreat in sedimentary tablelands have been rarely determined and their possible variability in relation to major environmental changes has often been speculative, especially in older contributions. Moreover, rates reported so far were almost exclusively from arid regions. In this paper we present a dataset of 20 cosmogenic exposure ages, obtained for cliffs and boulders produced by rock-slope disintegration, left in front of a retreating 150-m-high escarpment of a sandstone mesa in SW Poland. The most distant boulders are >400 m away from the cliffs. Following previous research in the region, boulders are mainly products of in situ disintegration and hence, their present-day position on the slope approximates the past position of the cliffs, allowing for the calculations of cliff retreat. Exposure ages systematically increase with the distance from the present-day cliff line and cover the last 100 kyr, implying an average retreat rate of 4.18 mm/yr. However, the dataset splits into several sub-populations, each with its own trend, meaning that the rates of retreat varied with time. A maximum was reached during the Late Pleistocene and transition to the Holocene, when the rates exceeded 10 mm/yr and may have reached 100 mm/yr. The rates seemed distinctly lower between MIS5 and LGM and during the Holocene. We propose that the transition towards a warmer climate at the Pleistocene/Holocene boundary, with an increased frequency of freezing-thawing cycles, the degradation of permafrost and unblocking of groundwater drainage enhanced caprock disintegration and accelerated the break-off rates of caprock. During periods of most efficient cliff disintegration and boulder production the rates of escarpment retreat at the field site could have been two orders of magnitude higher than in the hyperarid areas. However, despite changing rates of retreat major processes involved in escarpment evolution seem to have remained the same. [ABSTRACT FROM AUTHOR]

• The VMD decomposition processing module can improve prediction accuracy. • VMD-CBiLSTM can improve the accuracy of drought prediction in arid and semi-arid regions. • The VMD-CBiLSTM prediction model has good stability. Drought can cause great harm and loss, so accurate and efficient drought prediction has certain research significance. In previous studies, a single machine learning model is often used to predict the factors related to drought, such as precipitation and temperature, to indirectly explain the influence degree of drought, but the overall prediction accuracy is low, which can not fully and effectively predict the nonlinear and non-stationary drought characteristic information. In this paper, the variational modal decomposition model (VMD) is used to decompose the meteorological drought time series, and the convolution neural network (CNN) and the improved bidirectional long short-term memory neural network (BiLSTM) are combined to construct the meteorological drought hybrid prediction model (VMD-CBiLSTM). The research results show that using VMD-CBiLSTM model to forecast the monthly daily evapotranspiration deficit index (DEDI) of three weather stations, compared with the results predicted by VMD-LSTM, VMD-BiLSTM and VMD-ARIMA models, the average prediction accuracy R2 is increased by 0.076, 0.034 and 0.328 respectively, and the average RMSE is decreased by 0.178, 0.094 and 1.373 respectively. Compared with single model, VMD-CBiLSTM can not only reduce the uncertainty of meteorological drought prediction caused by climate model heterogeneity, but also improve the accuracy of drought prediction in arid and semi-arid regions, which can provide reference for coping with drought occurrence and drought early warning in advance. [ABSTRACT FROM AUTHOR]

This paper explores the environmental hazards associated with nuclear facilities in arid regions, focusing on the rapid migration of radionuclides facilitated by flood runoff resulting from extreme rainstorms. Through a case study of a proposed nuclear facility site in China, the study developed a comprehensive model to calculate the transformation of 90Sr and 137Cs in flood and subsurface water during accidents. The methodology employs a combination of field tests, radionuclide adsorption tests, the SWAT model, and the HGS model to create a fully integrated model. This approach allows for the several complex couplings (radionuclide–flood runoff–subsurface water) that have not been previously examined in the reactive solute transport. The findings reveal that despite groundwater movement being relatively sluggish, 90Sr and 137Cs migrate downstream rapidly due to their transportation by floods, which permeate the Upper Pleistocene gravel aquifer along the route. The study underscores the importance of considering the migration of radionuclides carried by floods generated by extreme rainstorms, as it poses a significant risk that cannot be ignored. [Display omitted] • A fully integrated model is established. • Reflect several complex couplings in reactive solute transport. • Field tests, adsorption tests, SWAT model, HGS model are combined. • Calculate the transformation of 90Sr and 137Cs on flood runoff and subsurface water. [ABSTRACT FROM AUTHOR]

• A framework for analyzing urban resilience through the life circle lens was developed. • The spatial match between urban pressures and resilience was examined. • Strategies for a multi-center, cluster-type urban resilience typology were outlined. • A people-oriented resilient planning was advocated. This paper presents an original framework for assessing and enhancing urban resilience from the perspective of the life circle that emphasizes the daily activity spaces of residents, using Urumqi, a major city in northwest China's arid oasis region, as a case study. Based on multi-source urban geographic big data, we introduce Gini coefficient and Lorenz curve to analyze the spatial matching relationship between urban spatial pressure and urban spatial resilience, and divided the priority of planning intervention by priority index. Our findings for the case study Urumqi reveal a strong "center-periphery" structure of urban resilience and spatial pressures. Based on the findings, we proposed targeted planning interventions prioritized by a resilience index that considers the life circle to address disparities and improve urban resilience. Our study advocates for urban planning to focus on the life circle, aiming to develop a multi-center and cluster-type resilient urban spatial structure to foster a "people-oriented" resilient city. [ABSTRACT FROM AUTHOR]

This paper explores water justice struggles in the understudied region of Iraq and Iraqi Kurdistan through a focus on two water justice movements, one civil society campaign, and a related event. While most of the relevant literature in geography and cognate fields has thoroughly dissected inter-State hydropolitical quarrels, discussed water justice from a legal perspective, and analysed water conflicts, less attention has been paid to bottom-up movements, to their visions and actions within a materially and socially challenging environment, and to their engagement with the state. Relying on published material as well as primary research, we show how Iraqi water activists seek to strike a balance between engaging institutions and moving beyond them, across ethno-religious divides and advocacy registers, in their quest to re-signify and re-common waterscapes. We argue that it is not despite all odds, but rather because of all odds, that Iraqi activists showcase such a developed awareness of their role and transformative potential along the rugged path of democratisation. [ABSTRACT FROM AUTHOR]

Groundwater is a crucial resource for dryland regions such as this, where surface water resources are limited and unreliable. This paper presents a study of the Lodwar Alluvial Aquifer System (LAAS) in northwestern Kenya and its hydrochemical and isotopic characteristics, with the goal of understanding how to sustainably manage the groundwater system. As a result, the paper focuses on elucidating the hydrogeochemical and river-groundwater interaction (using environmental isotopes and major ion chemistry) of an aquifer that is located in the north-western dryland of Kenya. The study utilised environmental isotopes of oxygen-18 (18O), deuterium (2H), and tritium (3H) as tracers for establishing recharge sources and origin of groundwater. A sampling campaign involving 112 water samples was conducted to establish isotopic compositions of rain, spring, surface water (rivers, scoop holes, dams and lake) and groundwater at the peak of the wet season in May 2018. The tritium values in the study area ranged from 1.1 to 2.4 TU. Considering the median values of δ18O and δ2H in surface water and groundwater samples, four clusters emerge based on the degree of enrichment; Cluster 1 comprises the lake water (δ18O = +6.01, δ2H = +41.9); Cluster 2 is the Turkwel and Kawalase river water with slightly positive relative to VSMOW and with different δ2H values (+7.6‰ versus −9.8‰). The third cluster is the groundwater of the Shallow Alluvial Aquifer (SAA) and the Deep Aquifer (DA) (δ18O = −0.96‰ and −0.70‰; and δ2H = +0.4‰ and +0.6‰, respectively). The last cluster comprises the most isotope-depleted waters of water pans, scoop holes, Intermediate Aquifer (IA) and Turkana Grit Shall Aquifer (TGSA) with median values ranging from −2.87‰ to −2.48‰ for δ18O and −8.6‰ and −16.4‰ for δ2H. While the SAA is mainly recharge by the Turkwel River, a relationship is observed between the values deuterium in the Kawalase (−9.6‰ VSMOW) and IA (−8.6‰ VSMOW). Understanding recharge sources and aquifer vulnerability of similar strategic aquifers helps scientists appropriately advise policymakers and the water community who develop sustainable water use, aquifer protection and conservation strategies. In addition, the study contributes scientific evidence of isotopic compositions of groundwater in the Horn of Africa. Furthermore, the evidence of surface water-groundwater interaction presents a case of a fragile dryland ecosystem. Future work will involve the installation of piezometers in strategic aquifer zones to monitor groundwater levels in relation to river gauging data to quantify the amount of recharge and establish the impacts of rainfall variability in the upstream catchment. • Hydrochemical and isotopic composition of LAAS inform urban groundwater management. • Tritium occurrence shows aquifers' vulnerability to human and climate factors. • Study enriches isotopic groundwater knowledge in the Horn of Africa. • Aquifer insights aid sustainable groundwater policies in global urban drylands. [ABSTRACT FROM AUTHOR]

• This paper constructed a framework for green water assessment in the Loess Plateau gully region using MIKE SHE model. • A new concept and extraction method for green water components was defined based on existing research. • A new concept of the potential of green water was defined in relation to the dried soil layers' classification indicators. • We assessed the dependence on green water components and potential for environmental changes. Exponentially increasing water demand and increasingly uncertain hydrological conditions due to climate change (CC) and land use/cover change (LUCC) undoubtedly pose significant challenges to the sustainability of water systems in arid and semi-arid regions worldwide, and even more so in the rain-fed agricultural area of the Loess Plateau (LP) in China, where green water supports all ecological landscapes and most agriculture. Therefore, an accurate assessment of green water resources is crucial for regional development. This paper constructed a comprehensive framework for assessing green water resources based on the MIKE SHE model, defined a new concept of green water components (GWCs) that can be extracted based on existing studies, proposes the potential of green water (GW P), and present a research methodology. To validate this research framework, we applied it to a typical basin in the LP gully area of the Nanxiaohegou (NXHG) basin. The model was calibrated using runoff data from basin outlet stations to extract four GWCs: high-efficiency green water (GW H), low-efficiency green water (GW L), unused green water (GW U), ineffective green water (GW I). We then assessed the GW P of the basin and analyzed its trends, consistency, and dependence on changing environments. The assessment framework is simple and easy to use, providing valuable information for regional revegetation and basin water management, and is highly recommended for replication in other regions. [ABSTRACT FROM AUTHOR]

• Residential Solar Blocks are reconceptualised in a hot-arid climate. • GAs are used for MOO of microclimatic and energy performance of the blocks. • Pareto optimal solutions had 12 m interspaces and orientated NE-SW and NW-SE. • Optimal solutions could reduce cooling loads by 31.7% and reduce UTCI by 1.6 °C. • Optimal solutions could increase the percentage of exposed surfaces in winter by 4%. Courtyard blocks are well known for their tempering potential of the thermal conditions in various climates. In this paper, the building heights, orientation and interspaces of courtyard blocks are optimised for the hot-arid climate of Cairo, Egypt. Simulations are conducted using an evolutionary search algorithm within the Grasshopper parametric design environment for Rhino 3D. The Ladybug-tools, plugins of Grasshopper were used to calculate the objective functions, the summer weekly cooling loads and the weekly average Universal Thermal Climate Index (UTCI). For three courtyard block types elongated 1, 2 and 3-fold the width of the inner court, the Pareto optimal sets of the three types all comprised solutions with the minimum interspaces. Orientation 45° was predominant in the square type, whilst orientation 135° was predominant in the elongated types (W/L = 2, 3). Using the weighted sum ranking, with the exception that orientation 45° was preferred in the most elongated type, the optimal solutions reduced cooling loads by up to 31.7% and reduced UTCI by up to 1.6 °C, compared to a reference case. Solar radiation analysis showed that the optimised cases have great potential to increase the percentage of exposed surfaces by 4% to reduce the heating loads in winter. [ABSTRACT FROM AUTHOR]

• A MGWR-based SMAP soil moisture product downscaling method is proposed. • The method considers the scale differences in the impact of surface variables on soil moisture. • Field validation shows higher accuracy from the downscaled SM than the SMAP SM itself. • This proposed downscaling method performs better than the traditional GWR and MW methods in the semiarid area. Passive microwave remote sensing missions such as Soil Moisture Active Passive (SMAP) are widely used for global soil moisture (SM) estimation. But the low spatial resolution of passive microwave SM products limits their applications at regional and local scales (normally 1–10 km). Using high-resolution auxiliary data to downscale passive microwave SM products is the primary way to obtain high-resolution SM data. However, the existing SM downscaling methods do not entirely account for the scale differences in the impact of various variables on the distribution of SM. To solve this problem, this paper introduced MGWR (Multiscale Geographically Weighted Regression) as a novel way to analyze the scale differences of normalized difference vegetation index (NDVI) and land surface temperature (LST) on the spatial pattern of SM. Accordingly, a new spatial downscaling algorithm for SMAP SM products is proposed and compared with the geographically weighted regression (GWR) algorithm and moving window algorithm (MW). The algorithm was applied to data taken during the SMAP Validation Experiment 2016 (SMAPVEX16), and the downscaled SM evaluated with in situ SM and aircraft observations. These results show that: 1) the SM downscaling conversion function, based on the MGWR, effectively reveals how different surface parameters relate to SM, with LST influencing SM globally and NDVI affecting it locally, 2) compared with GWR and MW, the 1 km SM obtained by the MGWR-based downscaling method showed better spatial agreement with airborne SM in the semiarid region with the ubRMSE decreasing by 0.023 m3/m3 and 0.026 m3/m3 for GWR and MW respectively, 3) when evaluating the 1 km SM with in situ SM in the semiarid region, the SM obtained through MGWR exhibited lower ubRMSE values as compared to both GWR and MW. Specifically, the median ubRMSE values for MGWR, GWR, and MW were 0.043 m3/m3, 0.053 m3/m3, and 0.094 m3/m3, respectively. In conclusion, this study demonstrates that MGWR can effectively improve the accuracy of downscaled SM in semiarid regions. [ABSTRACT FROM AUTHOR]

Desertification in karst is an effect of climate change and not sustainable anthropogenic activities, the combination of which, however, causes the gradual loss of karst natural resources, such as soil, vegetation, and groundwater. A considerable percentage of global karst areas is found in drylands, characterized by negative water balance and scarce presence of soils. High fragility of the karst environment, and its vulnerability to land degradation and pollution because of the peculiar anisotropic setting, environmental dynamics, and of the direct connection between the surface and the subsurface, are at the origin of the severe problems deriving from desertification processes in karst. In addition to natural drivers, such as geology and topography, karst desertification is generally due to four main factors, mostly or partly related to human activity: deforestation, improper land use, groundwater overexploitation, and climate changes. Through the analysis of a collection of studies conducted in several karst territories around the world, the present paper aims to provide an overview of the processes leading to desertification risks in karst areas. Emphasizing the need to preserve these fragile environments, characterized by peculiar features and precious freshwater resources, this review summarizes the main situations at the global scale of rocky desertification in karst, at the same time providing indications for developing innovative and multi-disciplinary approaches addressed toward mitigation of the risk related to desertification in karst. [ABSTRACT FROM AUTHOR]

This paper aims to assess the mean precipitation and precipitation extremes over Iran as simulated by the Regional Climate Model (RegCM4). A simulation spanning 20 years (1991–2010) at a horizontal resolution of 20 Km is driven by the NCEP / NCAR reanalysis. We evaluated the model by comparing simulated precipitation with observations using Bias, Root-Mean-Square Error, and Index of Agreement metrics. We examined the extreme precipitations based on a set of extreme indices recommended by the Expert Team on Climate Change Detection and Indices (ETCCDI) in three categories of intensity (Rx1day and SDII), duration (CDD and CWD), and frequency (R10mm and R20mm). The linear trends are calculated using the Theil–Sen estimator method, and the statistical significance (95% confidence level) is determined by using a modified Mann-Kendall (MMK) trend test. The RegCM4 model satisfactory captured the spatial distribution of precipitation and precipitation extremes, although high bias remained in small parts of Iran, including the northwest and southeast. The northwest bias is due to spring convectional precipitation and the southeast bias could be caused by precipitation from the Asian summer monsoon system, which both of them may not be well simulated by the applied Grell convective scheme. Results indicate that the model reasonably captures Rx1day, SDII, CWD, R10mm, and R20mm Indices over Iran. In good agreement with precipitation observations, the southern coast of the Caspian Sea represents the second-highest extreme precipitation, except for SDII, which is probably due to the high frequency of rainy days in this region. The highest CDD of more than 200 days is found in the arid and semi-arid regions of the southeast. In general, precipitation decreased in most regions of Iran, especially the western, southern, and interior regions. In addition, the results reveal that heavy (R10mm) and very heavy (R20mm) precipitation events have also decreased in the same regions. Results also emphasize an increase in consecutive dry days (CDD) in most parts, especially in the southeast, which deserves more attention in future research. The decreasing trend of precipitation and the increasing trend of CDD show that Iran has become drier in the 2000 s compared to the 1990 s • The Grell convective scheme applied in RegCM4 has been successful in simulating precipitation extremes in Iran. • The RegCM4 has been able to capture precipitation extremes well in Iran. • Consecutive dry days (CDD) are increasing in most parts of Iran. [ABSTRACT FROM AUTHOR]

• Connectivity of riparian vegetation, transpiration and evaporation was assessed. • Evaporation is lower (18 %−34 %) near high riparian vegetation density (NDVI ≥ 0.6). • Riparian vegetation actively lower evaporation up to 90 m from the reservoir margin. • Riparian vegetation transpiration and reservoir evaporation ratios are equivalent. • 275,000 people may be supplied per day by the evapotranspiration losses. Understanding the combined open water reservoir evaporation and riparian vegetation transpiration (evapotranspiration) is important for water resource management in semiarid regions like the Brazilian Dryland region. Existing research has explored reductions in open water evaporation due to riparian vegetation transpiration, but evidence for this interdependence in this region is not well understood. The aim of this study was to estimate the connectivity (impact and maximum distance of action) between riparian vegetation and its transpiration and reservoir evaporation, as well as the ratio of the volume losses by transpiration and evaporation, using Landsat 5 and 8 in a Brazilian Dryland environment. Evaporation and transpiration were estimated using the Surface Energy Balance System for Water and the Surface Energy Balance System models, respectively, from 1985 to 2020. A Class A Pan and the Penman-Monteith equation were used, for reference reservoir evaporation and vegetation transpiration, respectively. The occurrence of riparian vegetation was associated with the Normalized Difference Vegetation Index. Both models performed well, with root mean square error ≤ 0.80 mm/day. The riparian vegetation transpiration demonstrated a high negative correlation (R²>0.7) with evaporation, suggesting the vegetation acts to reduce evaporation (average of 30 %) up to a maximum distance of 90 m from the reservoir shoreline. This is explained by the adjacent riparian vegetation-induced reduction in radiation inputs due to shading at the reservoir margin, a lowering of wind speeds and increases in air humidity from transpiration. The ratio of riparian vegetation transpiration to reservoir evaporation within a buffer of 150 m is approximately equal. Combined riparian vegetation and reservoir evapotranspiration equates to the daily water supply for ∼275,000 people. The paper explains and quantifies the connectivity between riparian vegetation transpiration and reservoir evaporation, thereby providing a model for improved reservoir water balance estimates, which can aid regional water resources planning, development, and management. [ABSTRACT FROM AUTHOR]

The vadose zone serves as a crucial link for the mutual transformation of atmospheric, surface, ecological, and groundwater systems. Infiltration recharge in the vadose zone is a key step in the Earth's water cycle and plays an extremely important role in the sustainable development of groundwater resources, particularly in arid and semi-arid regions. However, under the influence of extreme climatic conditions and intense human activity, the vadose zone has thickened in many places globally. Changes in the vadose zone structure lead to alterations in the infiltration process. Researchers have attempted to quantify this process using various methods. However, it has been found that conventional monitoring methods are inadequate to effectively describe the complex infiltration recharge process under the multifactorial influence of a deep vadose zone. Through an analysis of relevant literature published from 2000 to 2023 regarding deep vadose zone infiltration recharge, this paper identifies four contentious bottlenecks: (1) effective monitoring and simulation of deep vadose zone infiltration recharge, (2) modes of deep infiltration recharge, (3) issues related to the quantity and recharge period of precipitation and irrigation infiltration recharge, and (4) quantification of spatial variations and scale effects of infiltration recharge. After reviewing the latest developments in infiltration recharge monitoring and simulation and systematically analyzing the influencing factors and mechanisms of deep vadose zone infiltration recharge, this study provides answers to the aforementioned issues. The combined use of monitoring and numerical simulation methods, taking into account infiltration recharge scenarios and scales, can enhance the reliability and accuracy of the calculation results. Additionally, piston flow may not be the primary mode of water movement in the deep vadose zones. Understanding the modes and characteristics of water movement, as well as the differences in suction and desorption processes, is fundamental for accurately describing nonlinear infiltration recharge processes. Furthermore, the measured average vertical infiltration rates of the deep vadose zone vary widely from 0.14 to 500 mm/d globally. In the North China Plain, vertical infiltration recharge rates range from 133 to 300 mm/a. These significant differences are related to the research scale, external conditions, and internal soil structure within the vadose zone. Finally, a systematic analysis of the driving factors of nonlinear infiltration recharge in the deep vadose zone is a prerequisite for quantifying spatial variations and scale effects. Only by fully considering the interactions and contributions of various driving factors can the spatiotemporal variations in soil infiltration be effectively quantified. Therefore, our research team suggests that future studies on deep vadose zone infiltration recharge should focus on establishing a unified layout for large-scale, multi-point, synchronous, in situ, and long-term monitoring; constructing relationships between the vadose zone structure and hydraulic characteristics; and conducting comprehensive studies on the overall water cycle in the Earth's surface layers, with the deep vadose zone as the core. These will help build a research system for the spatiotemporal infiltration recharge of water in the deep vadose zone at multiple layers and scales, achieving the closest approximation to a realistic description of the deep vadose zone infiltration recharge. [ABSTRACT FROM AUTHOR]

A rich insect fauna is found in the Cretaceous (Aptian) Nova Olinda Member of the Crato Formation in the Araripe Basin, northeastern Brazil. The Crato Formation was deposited close to the centre of the supercontinent Gondwana, prior to significant rifting. In this paper, we analyzed remains of 1135 insect specimens, representing 55 families, within two limestone facies of the Nova Olinda Member: pale yellow and dark gray limestones. We collected taphonomical data and assessed the paleoecological significance of insect faunas in terms of their distribution and interaction with the paleoenvironment. The insect fauna is dominanted by fully terrestrial taxa despite preservation in an aquatic paleoenvironment. Considering both facies, the distribution of insect families is similar throughout the Nova Olinda Member, which excludes possible overlapping of one entomofauna over another. The pale yellow limestones near the top of the section are richer in fossil insect content and show a higher incidence of aquatic and semiaquatic insects preserved in dorsoventral view compared to the dark gray limestones. This suggests that the Crato insects preserved in the pale yellow limestones experienced short transport distances or prolonged decay or both. In contrast, insects preserved in the dark gray limestones appear proportionally with higher degrees of disarticulation than those preserved in the pale yellow limestones, indicating that these insects underwent a higher degree of postmortem transport in the biostratinomic stage. Compared to descriptions of other Early Cretaceous assemblages, the taxonomic literature of Crato Paleoentomofauna shows distinct differences. The Yixian and Zaza formations are described as being dominated by beetles and wasps. The Crato Formation, however, is relatively richer in Paleoptera species. Both the sedimentary facies studied and the paleoentomological content reveal a complex ecosystem inserted in a depositional setting, similar to modern long-standing wetlands, and where periodically flooded zones were surrounded by dry lands with xeromorphic vegetation. • Crato insects preserved in the dark gray limestones appear proportionally with higher degrees of disarticulation. • The paleoentomological content reveals an ecosystem inserted in a setting similar to modern long-standing wetlands. • Compared to other Early Cretaceous assemblages, the Crato Paleoentomofauna is relatively richer in Paleoptera species. [ABSTRACT FROM AUTHOR]

Surface emissivity (ε) is used to characterize surfaces and to determine surface temperature from thermal radiation data. While in many applications it is treated as a constant, it is known to change with surface water content. Several ASTER/SEVERI based studies have speculated that diurnal changes in ε over deserts are linked to diurnal soil water content cycles resulting from water vapor adsorption during the night and subsequent evaporation during the day. This paper aims, for the first time, to validate the relationship between diurnal changes in surface ε and the changes in soil water content due to water vapor adsorption and evaporation under natural conditions. Measurements were conducted with a 6-band infrared radiometer, designed to validate ASTER bands 10–14, with study-specific recalibration for improved accuracy of ε. The evaluation included two different approaches to determine ε : using a single reference band (1B) and using the temperature/emissivity separation algorithm (TES). water content. While the TES has proven itself in many applications, it was found that for the soils studied (sand and loess) the use of 1B approach gave more consistent results for ε changes with soil water content than TES. Emissivity could be a powerful tool to characterize little studied soil water content changes in arid regions, but will require better characterization of surface properties to quantify the relationship between ε and soil water content for various soil types. Additional challenges to upscale this method include properly accounting for air irradiance and spatial heterogeneity. Meeting these main challenges will lead the way to detect small changes in soil water content under dry conditions at larger scales. Whether these are a result of water vapor adsorption or other processes, detecting such small changes in soil water content will provide new insights into desert hydrology. • On-ground validation of an infrared radiometer with ASTER bands. • Calibration and measuring protocol for minute changes in emissivity. • Observed emissivity changes of 0.2–0.6 due to water vapor adsorption. • Main challenges: air radiance, surface heterogeneity, and soil spectral properties. • Potential for new insights into desert hydrology. [ABSTRACT FROM AUTHOR]

• A new vacuum saturation device for high-suction tensiometers was proposed. • The new device significantly improved the measured range of suction. • We analyzed the response characteristics of an insertion tensiometer. • The developmental stages of the tensiometer response curve were suggested. Tensiometers are devices that can be used to monitor suction variation in landslides and slopes. The soil suction that can be measured with a conventional tensiometer is limited to 85 ∼ 90 kPa due to water cavitation in the tensiometer. This low measurement range of suction may be insufficient to interpret and determine the hydraulic properties of unsaturated soil, especially in semihumid and semiarid climate regions. However, in most geotechnical engineering studies, conventional tensiometers are still utilized. Although several types of high-suction tensiometers have been developed in recent decades, high suction measurements are difficult in the field because the saturation procedures for these tensiometers are complex and time consuming. Hence, the development of a simple and rapid saturation method is necessary to support their application. The vacuum saturation technique is a simple and reliable technique for saturating the porous ceramic cup of a tensiometer. However, if a high-suction tensiometer is saturated via a vacuum syringe, the measurable maximum suction is usually<200 kPa, which limits the application of tensiometers in geotechnical engineering. In this paper, we proposed a simple saturation device and a saturation method (the vacuum cylinder saturation method, VCSM) to saturate high-suction tensiometers. Soil column experiments were conducted to investigate the advantages of the VCSM and the response characteristics of insertion tensiometers. The results indicated that high-suction tensiometers could easily and steadily measure a maximum suction of 350 kPa if saturated via the VCSM. The VCSM could effectively prevent or retard the occurrence of cavitation due to the high vacuum pressure and slow progress of water filling in the tensiometer shaft. In addition, the response curve of insertion tensiometers could be divided into three stages: installing disturbance stage, delayed response stage and equilibrium stage. The extent of the disturbance caused by insertion tensiometer installation is a key factor influencing the delayed response characteristics of the tensiometer response curve. This paper also provides greater insight into the saturation method of tensiometers and the application of insertion tensiometers. [ABSTRACT FROM AUTHOR]

In this paper we build a water conflict typology and discuss some applications for water resources planning and management. To show how a typology was built we highlight twelve well documented water conflicts historical cases in the semiarid region of Ceará state and water conflicts collectively identified by river basin committee members in four water resources river basin plans. To show how the typology works we applied it to contemporary cases of water conflicts headlined in the national media. Conflicts are separated into component characteristics such as triggers, actors, length, coverage area, mediation arena, and other useful information. As the complexity of social-environmental issues increases new tools for organizing data into useful information increase in demand. We believe that this water conflict typology can be employed as an analytical instrument capable of providing a "bird's-eye view" of diffuse sources of conflict. [Display omitted] • Typologies can play a key role in organizing diffuse but crucial information for water management. • Few typologies focus on water conflicts. • We show how a water conflict typology can reveal patterns that are vital for water management decision-making. [ABSTRACT FROM AUTHOR]

The present form of Urbanisation Pattern in India cannot sustain the water requirements in cities, especially in semi-arid regions of India. The tacit knowledge of water resilience has been used since time immemorial to tap and address water demand and risk in India. Now is the right time to blend the traditional and modern technology to address water issues for water resilience. This paper explores the traditional knowledge and its usage in water management system in semi-arid areas and how water resilience can be achieved through co-production of water at a local level in Jodhpur City in the state of Rajasthan. It explores how the water system has been losing its value due to degradation caused by the spatial expansion of the city. It analyses water stress both in terms of water scarcity as well as managing the excess. Using primary and secondary data gathered, the paper proposes ways of co-production of water with community for sustainability and resilience. It suggests eco-restoration of traditional water system, importance of inclusion of varied actors, etc in addition to addressing SDG 6, and using ISO/BIS standards for water resilience. • Water stress to be a critical aspect for sustainability of cities in India. • Importance of integration of tacit/traditional knowledge with explicit knowledge. • Co-production of water for addressing issues related to water resilience. • ISO/BIS standards as a tool for assessing performance on water resilience. [ABSTRACT FROM AUTHOR]

[Display omitted] • NDVI shows an overall increasing trend from 2000 to 2020. • The Hexi region shows a warming and wetting trend. • Extreme precipitation is more important for NDVI. • The lag effect of NDVI on climate extremes varies by indicators and spaces. Climate extremes significantly affects vegetation dynamics, and understanding the relationship between dryland vegetation and climate extremes is crucial for regional ecological security and disaster warning. According to meteorological and satellite remote sensing data, the paper analyses the dynamics of normalized difference vegetation index (NDVI) and climate extremes in the Hexi region from 2000 to 2020 using Theil-Sen Median, Mann-Kendall and linear regression methods; the relationship between climate extremes and vegetation dynamics is revealed using Pearson correlation and boosted regression trees (BRT) models. On this basis, the time-lag effect of NDVI in response to climate extremes was further investigated. The results show that the NDVI in the Hexi region increased from 2000 to 2020, with significant greening (67.72 %) and a small amount of degradation concentrated in the desert in the northwest and the oasis in the southeast. The correlation between climate extremes indicators and NDVI shows a large spatial heterogeneity, with extreme precipitation showing a high importance for all regions except oasis. NDVI has no lag or 1 month lag for extreme temperature, no lag for max 1-day precipitation amount (Rx1day) for areas other than mountainous areas, and a 3-month lag for max 5-day precipitation amount (Rx5day) for extensive areas. The results of this study could serve as a reference for the study of the relationship between vegetation dynamics and climate extremes in arid and semi-arid regions, and provide a theoretical basis for the establishment of scientific and reasonable strategies for regional vegetation restoration and conservation. [ABSTRACT FROM AUTHOR]

[Display omitted] • Five discharge datasets have median correlation coefficients > 0.6 with the observations. • Overestimation of monthly mean flow is more common than underestimation. • GRFR showed the best estimate at around 40% of the locations. • None of the models provides good estimates for rivers and streams in arid regions. High-resolution global flow discharge datasets are critical to understand the terrestrial water cycle and river ecosystem services. Recently, a number of global hydrological models have been developed to capture global river flow dynamics at locally relevant scales. However, the relative accuracy of these simulated flow discharges is largely unknown. In this paper, using the largest observed streamflow datasets from > 26,000 gauging stations, we evaluated the performance of monthly and sub-monthly flow variation (1980–2014) generated from five major global hydrological models, Catchment-based Macro-scale Floodplain model (CaMa-Flood), Global Flood Awareness System (GloFAS-reanalysis), Global Reach-level Flood Reanalysis (GRFR), PCRaster GLOBal Water Balance model (PCR-GLOBWB), and Water Global Assessment and Prognosis (WaterGAP). Significant spatial heterogeneity in model performance was identified. We found that estimates by all five discharge datasets have a relatively high correlation with the observations (medians > 0.6). But none of them showed adequate correlations between simulated and observed flows for systems in Southwest or Central U.S.A., South Africa, or South Australia. Across all models, overestimation of monthly mean flow was more common than underestimation and high flows at a sub-monthly scale were more accurately characterized than low flows. Performance of all models was poor in Africa and Oceania. No single model performed universally best at all gauging stations, but GRFR showed the best estimate at around 40 % of the locations. None of the models provided satisfying estimates for rivers and streams in arid regions. We also found a significant negative effect of flow regulation on the predictive accuracy of all models. Our study highlights the importance of thorough evaluation of global discharge datasets before their local and regional application and provides guidance for future enhancement of global hydrological models. [ABSTRACT FROM AUTHOR]

• Drought followed by extreme rain/flooding exposed vulnerabilities in Ceará, Brazil. • Adaptative strategies in dry periods may become maladaptive during extreme rain. • Impacts of and responses to drought, extreme rain, and flooding are interrelated. • Hydrometereological extremes should be considered together in semi-arid regions. As climates continue to change, semi-arid rainfall regimes are projected to become increasingly more extreme, with longer dry periods and fewer, but more intense, heavy rainfall events. This process of hydroclimatic intensification increases the risk associated with successive extreme climate hazards, such as drought and then heavy rainfall, in the same area. However, the development of effective adaptation strategies to drought, heavy rainfall, and flood hazards is hampered by the lack of integrated analyses that consider the interactions among these hazards and responses to them. To increase understanding of these interactions, this paper examines impacts of and adaptive actions taken in response to prolonged drought (2012–2018) and subsequent extreme rainfall and flooding (March and April 2023) in the semi-arid region of Ceará, Northeast Brazil. We find that policies and adaptive measures focus primarily on drought hazard, while preparation for extreme rainfall events and flooding is scant. Management plans and long-term adaptive strategies are being developed for drought and not other extreme hydrometeorological events. Additionally, emergency measures for extreme rainfall and flooding are much less structured than those for drought. As such, the paradigm "Convivência com o semiárido" ("Living with the semi-arid region") remains limited to adapting to drought hazard, ultimately hindering adequate extreme rainfall and drought responses. To promote more effective adaptive strategies in the context of hydroclimatic intensification in semi-arid regions, drought, heavy rainfall, and flood responses must be considered in a more integrated manner to create management plans to prepare for the potential impacts of these hazards into the future. [ABSTRACT FROM AUTHOR]

• Quantitatively describes the groundwater recharge process for lakes. • Constructed a model for the groundwater table-lake area relationship in groundwater-dependent lakes in arid regions. • Suggested a groundwater depth of 1.73 m to maintain stable lake area within the Hetao Irrigation District. • Constructed model can serve as an effective reference tool for groundwater management and the protection of lake ecosystems. The groundwater table constitutes a significant factor in sustaining the ecosystems of lakes in arid regions. To elucidate the mechanism by which variations in groundwater tables affect lake areas, this paper presents a case study of a typical groundwater-fed lake in China's Hetao Irrigation District. An analytical model correlating groundwater tables with lake areas was developed to simulate and predict the impact of changes in groundwater tables on lake areas. The findings indicate that the analytical model adeptly simulates the lake area dynamics of the groundwater-fed lake cluster (Taerhu lake cluster) from 1998 to 2018, achieving a Nash-Sutcliffe efficiency (NSE) value exceeding 0.6 and a root mean square error (RMSE) value below 0.1 square kilometers. Maintaining a groundwater depth at 1.73 m ensures the stability of the lake area; a decrease in groundwater depth to 1.93 m would result in a 79.5 % reduction in lake area. The model constructed in this study offers a crucial tool for the ecological protection of lakes and groundwater management in arid regions. [ABSTRACT FROM AUTHOR]

[Display omitted] • Spring drought factors include snow cover, precipitation, temperature, and soil moisture. • Established a variance analysis projection pursuit model (ANOVA PPM) • ANOVA PPM achieves a balance between overall dispersion and local aggregation. Due to the influence of snow cover and soil freeze–thaw processes in the early spring, the characteristics of spring drought in cold regions are different from those in other regions. This paper takes Qiqihar, a cold and semiarid grain production area in Northeast China, as the study area. Based on factors such as snow cover in the early spring period and precipitation, temperature, evapotranspiration, and soil moisture during the spring sowing period, a projection pursuit model with analysis of variance (ANOVA PPM) was used to analyze the spatiotemporal variation characteristics of regional spring drought. For the ANOVA PPM, based on the grouping of the projection points, local aggregation is measured by the mean square within groups, and overall dispersion is measured by the mean square between groups, thus achieving comparability and balance between overall dispersion and local aggregation. The spatial analysis of spring drought showed that, from a spatial perspective, there were significant spatial differences in spring drought in different subregions, and spring drought was closely related to latitude, with significant differences occurring at different latitudes. The northern region is relatively light, while the central and southern regions are more severe. From a temporal perspective, there are significant differences in spring droughts between different decades (1980 s, 1990 s, 2000 s and 2010 s). Overall, spring drought first intensifies and then decreases. [ABSTRACT FROM AUTHOR]

• The runoff, sediment load and runoff erosion power decreased significantly. • Compared with runoff, runoff erosion power-sediment relationship is better. • The power function of runoff erosion power and sediment is better than linear. • Erosion in particular geographic locations responds strongly to runoff erosion power. In recent years, the acceleration of urbanization in the Yangtze River Economic Belt (YREB) has brought about problems such as soil erosion, ecosystem degradation and decline in ecological service functions. Therefore, this paper selects the Fujiang River Basin (FRB) in Upper Yangtze River (UYR), and analyzes the relationship between runoff erosion power (REP) and sediment transport (ST) on the basis of analyzing the variation characteristics of hydrological elements. Based on SWAT model, a variety of scenarios are set up to quantitatively analyze the impact of different land use changes on runoff and ST and REP in the basin. The results indicated that: (1) The annual precipitation in FRB from 1960 to 2018 did not change significantly, while the annual runoff, annual ST and annual REP decreased significantly. Compared with runoff and runoff depth, the relationship between sediment transport modulus (STM) and REP is the best, especially the power function between them is better than the linear function. (2) The results of the evaluation indexes of the simulation results of the SWAT model based on the measured runoff and sediment data from 2008 to 2018 are pass and above, that is, the simulation results are considered reliable. (3) Under the five scenarios of conversion of sloping farmland to forest, conversion of dry land to paddy field and conversion of grassland to bushland and forest land, the runoff and ST in the basin decreased but the overall range was small. The simulation results of SWAT model show that the erosion of specific areas in the basin shows the greatest degree of weakening with the decrease of REP. [ABSTRACT FROM AUTHOR]

Fluvial sediments preserve evidence of past hydroclimatic regimes and are important but potentially under-utilised indicators of palaeoenvironmental change in drylands. This paper presents a new chronological database of 603 ages from late Quaternary fluvial sediments at 70 sites in southern Africa's western dryland regions. This synthesis assesses the spatial and temporal trends in both the palaeoenvironmental record and the supporting data that underpins these interpretations. We find that topographic and climatic characteristics of river catchments influence the nature of fluvial archive formation and preservation. Channel confinement, legacies of research, and sampling strategies in specific river basins are found to control the sedimentary context and length of documented record available for palaeoenvironmental reconstruction. The age of dated deposits and associated magnitude of chronological uncertainties influence the temporal range and resolution of climate and fluvial variability that can be discerned. Where calendar year uncertainties are small enough, predominantly dating to the last millennium, individual flood events and multi-year episodes within flash flood deposits can be linked to synoptic climate patterns, yet when uncertainties are larger, interpretations are restricted to understanding multidecadal to centennial-scale phases of flow regimes. This paper collates a scattered literature to detail the current state of southwestern Africa's fluvial record and highlights opportunities for future research. We consider controls on fluvial archive interpretation that are pertinent to wider dryland contexts and argue that fluvial records provide useful information for inclusion in regional palaeoenvironmental syntheses. Following a filtering process, quality-assessed chronologies are compiled to establish the combined fluvial history of 22 rivers to consider the response of fluvial systems to hydroclimatic drivers. At the Last Glacial Maximum (LGM; 24–18 ka), records detail a regionally consistent signal of intermittent to perennial flow under relatively humid conditions in what are currently ephemeral systems. The mid Holocene (MH; 8-4 ka) is also characterised by the occurrence of sustained river flow and higher discharge events than present, but with greater spatial variability. Sedimentary archives display evidence of both intermittent flow and extreme flood events within ephemeral regimes, and two rivers, the Hoanib and Molopo, are characterised by reduced fluvial activity. Within the last millennium, flash flood regimes within an arid to hyper-arid climate were established with coherence in the timing of flood frequency variations recorded between catchments. • A new chronological database synthesises >600 ages from southwestern Africa's fluvial sediments. • Fluvial chronologies span the last 132 ka, with most studied sediments dated within the last 50 ka. • The combined record reveals enhanced hydrological activity at the LGM and mid-Holocene, and a flash flood dominated regime from 1 ka. • Analysis of topographic and climate setting establishes controls on archive formation and preservation. • Results highlight the utility of quality-assessed fluvial records as sources of palaeoenvironmental information. [ABSTRACT FROM AUTHOR]

Earth Observation (EO) technologies have played an increasingly important role in monitoring the Sustainable Development Goals (SDG). These technologies often combined with Machine Learning (ML) models provide efficient means for achieving the SDGs. The great progress of this combination is also demonstrated by the large number of software, web tools and packages that have been made available for free use. In this paper, we introduce a software architecture to facilitate the generation of EO information targeted towards soil moisture that derive several challenges regarding the facilitation of satellite data processing. Thus, this paper presents a web-based tool for Soil Moisture Estimation (SMETool), designed for the soil moisture estimation using Sentinel-1A and Sentinel-2A data based on Eo-learn library. SMETool implements several ML techniques such as (Artificial Neural Network (ANN), Random Forest (RF), Convolutional Neural Network (CNN), etc.). The SMETool could be very useful for decision makers in the region in assessing the effects of drought and desertification events. Experiments were carried out on two sites in Tunisia during the period from 2016 to 2017. Although the performance of the used models is very close, it is clear that CNN and RF outperformed other ML models. The achieved results reveal that the soil moisture, was highly correlated to the in-situ measurements with high Pearson's correlation coefficient r ( r RF = 0. 86 , r ANN = 0. 75 , r XGBoost = 0. 79 , r CNN = 0. 87) and low Root Mean Square Error (RMSE) (RMSE RF = 1.09%, RMSE ANN = 1.49%, RMSE XGBoost = 1.39%, RMSE CNN = 1.12%), respectively. • A new web-based tool for soil moisture estimation at the scale of arid regions. • Simple implementation using Eo-learn framework and machine learning methods. • A case study on arid region in southern Tunisia using Sentinel 1-A and Sentinel 2-A products. [ABSTRACT FROM AUTHOR]

• This biocrust special issue is a collection of 27 papers from 12 countries worldwide. • Various topics in soil-biocrust interactions in drylands are included and discussed. • Major topics include biocrust effects on soil hydrology, erosion, C, and biodiversity. • Biocrust and functional responses to physical disturbance and climate change are emphasized. • Biocrust conservation and restoration are considered important in combatting soil and land degradation. Biocrusts are photosynthetic biotic communities of cryptogams and microbes that aggregate minerals at the soil surface in many ecosystems. Due to their high tolerance to harsh environments, biocrusts are present in a wide range of habitats, but are especially representative ground covers in regions with restricted vegetation growth, such as drylands (hyperarid, arid, semiarid, and dry subhumid regions) where water is a limiting factor, or high latitude or altitude regions where cold is a limiting factor. Since biocrusts fulfill a large range of ecological roles particularly in modifying soil properties and regulating functions, their rehabilitation and management is believed to be a promising measure for combating land degradation. We organized this article collection to further highlight the importance of biocrusts and their fundamental roles in reshaping soil properties and multifunctionality in drylands and other ecosystems, and to elucidate the ways in which global change factors are influencing biocrust-soil systems. The special issue brings together 27 research articles pertinent to soil-biocrust interactions or biocrust response to global change and disturbance from 12 countries worldwide (10 papers from China, 6 papers from the USA, 2 papers from Spain, 2 papers from Australia, in addition to studies from Antarctica, Argentina, Brazil, Iceland, Iran, Mexico, Norway, South Africa, and Sweden). The discussed topics include biocrust roles in regulating soil hydrology (6 papers), reducing soil erosion (4 papers), affecting soil carbon fixation and respiration (2 papers), and influencing soil microbial biodiversity (5 papers). The responses of biocrusts themselves and their functions to trampling disturbance (2 papers), land use shifts (2 papers), and climate change (5 papers) are also emphasized. On the whole, we highlight the capability of biocrusts in reshaping most properties of surface soil, acting as engineers and architects of surface soil properties, functions, and processes in dryland or other harsh environments, and we recognize the necessity of their protection and consideration as valuable nature-based measures to combat soil and land degradation. [ABSTRACT FROM AUTHOR]

Indoor vertical farming can address future food insecurity by reducing land use and environmental dependence positively mitigating the environmental impacts associated with conventional agriculture. However, its high energy consumption and environmental impact raise concerns. This paper explores the use of Concentrating Solar Power (CSP) to power vertical farming in Iraq's arid regions, using abundant solar resources to reduce environmental impact and energy costs. The study evaluates the feasibility and benefits of integrating CSP technologies into sustainable agricultural practices, considering factors like implementation costs, energy production, and water usage. The study utilized the system advisor model (SAM) to carry out the techno-economic assessment by relocating existing commercial CSP plant in Seville, Spain to six Iraqi locations, following a comprehensive technical site assessment. The energy production level, capacity factor (CF), and levelized cost of electricity (LCOE) of the initial Spanish plant were lower than five of the six selected locations. Haditha and Ar Rutbha cities have the highest annual energy output, 123 GWh and 122 GWh, respectively, surpassing Seville's original plant output, which at 110 GWh performed less than Iraq locations. Next, comparisons are made between conventional farming and vertical farming (VF) cultivation. The study focuses on Romaine lettuce as the benchmark crop due to its prevalence in vertical farms and its suitability for arid climates. VF shows the potential to achieve yields between 41 and 68 kg/m2/y, 63 to 104 times higher than conventional farming in Western Iraq. VF's year-round cultivation with artificial lighting results in 83 times greater energy demands, requiring 25 kWh/kg/y. The findings emphasize the potential of CSP technologies to support sustainable agriculture in Iraq's arid regions. These findings demonstrate the possibility of utilizing solar power for sustainable agriculture in Iraq, offering valuable insights for policymakers and stakeholders seeking cost-effective and energy-efficient solutions. • Concentrating Solar Power and Vertical farming for sustainable energy in arid regions was investigated. • Techno-economic analysis shows the cost-effectiveness of CSP technologies in selected Iraqi locations. • CSP-powered vertical farming model has the potential to reduces land use, improves food security, and reduces the environmental impact of conventional farming. [ABSTRACT FROM AUTHOR]

Open water transposition channels in hot and arid regions lose significant amounts of water through evaporation. This is the case with the São Francisco River Integration Project (PISF) in Brazil. This paper proposes using photovoltaic (PV) panels to cover the channels of the PISF to reduce evaporation and save water. The study aims to evaluate the potential amount of water saved by this technology across all channel lengths, as well as the energy that can be generated by the covered watercourses. The study also examines whether the energy produced can be used to power the transposition pumps during peak radiation hours, improving the energy efficiency of the project. To achieve the study's goals, the authors conducted a thorough review of academic and industrial literature on the state-of-the-art of PV generation in Brazil and worldwide. They also examined the regional geography, meteorology, irradiation, and social characteristics of the area. The authors identified the characteristics of the channels and watercourses of PISF and calculated their solar potential. The study found that covering all current channel extensions with PV panels could save up to 25,000 m3 Water per day to supply the deprived population, improving their quality of life and generating 1,250 GWh annually. [Display omitted] • Use of photovoltaics approach to reduce evaporative water losses in channels. • The Largest River (PISF) transposition project case. • The use of PV panels to cover the PISF water courses. • Covering channel extensions with PV panels could save up to 25,000 m 3 Water/day. • Generating 1,200 GW h annually. [ABSTRACT FROM AUTHOR]

• Mg2+ removed efficiently by combining EID and MgNH 4 PO 4 precipitation methods. • Kinetic results show that the nucleation rate of Li 3 PO 4 is slower than that of MgNH 4 PO 4. • The residual Mg2+ is below 3 ppm with lithium loss 1.9 % in experimental. • The one-step Li 3 PO 4 fabrication process realizes efficient utilization of the material. The "aluminum adsorption + membrane" method is the mainstream technology for lithium extraction from salt lakes. However, the low adsorption capacity of aluminum adsorbent leads to massive freshwater consumption, which seriously limits its large-scale promotion in arid and water-scarce regions. Electrochemical intercalation/deintercalation (EID) method is a new technology for Li+ extraction with high adsorption capacity and good separation of Li+ and impurity ions. Based on this, a combined EID-MgNH 4 PO 4 precipitation technique is proposed for Li+ extraction from brine and Li 3 PO 4 preparation directly. Firstly, EID was used for high Mg/Li brine to obtain an anolyte with low Mg/Li; subsequently, Mg2+ was removed deeply from the anolyte by MgNH 4 PO 4 precipitation; finally, Li 3 PO 4 was prepared by adding phosphate. The results show that the Mg2+ concentration in the anolyte can be reduced to 3 ppm in the Mg2+ removal process, and the Li+ loss rate is less than 1.9 %. In addition, the overall recovery of Li+ exceeds 95 %, and the removal of Mg2+ is more than 99.8 % during the whole process. The combined EID-MgNH 4 PO 4 precipitation technique proposed in this paper is expected to provide more references for developing lithium resources in arid and water-scarce salt lakes regions. [ABSTRACT FROM AUTHOR]

• Various Connectivity Index models are tested in a Mediterranean terraced catchment. • The Index using vegetation Weighting factor simulates the field pattern best. • All the indices are poor at replicating sedimentation and disconnectivity. Connectivity analysis has proved a very valuable approach in understanding runoff and sediment fluxes in catchments. Many analyses use Connectivity Indices to model the patterns, but various versions of the Index have been developed. This paper tests the effects of these variants of the Index as applied to an agricultural-terraced catchment in the semi-arid Mediterranean region where occurrence of connectivity is relatively well documented to validate the modelling. This paper compares three versions of the Connectivity Index that use vegetation/land use (C), topography (RI) and roughness (n) as the weighting factors. Two different slope algorithms are also tested. The weightings are derived from a UAV (drone) survey, with simultaneous ground field mapping. The UAV imagery is found to provide a good, high resolution basis for determining detailed topography and vegetation cover. The slope limit present in some modelling is found to be unsuitable in this landscape where steep terrace embankments that are vegetated in places, and also partially vegetated uplands, occur. Subsequent modelling removed the slope limit. The major patterns of flow produced are similar between the models and are largely related to the overall topography and major drainage lines but considerably modified by the terracing. The model outcomes differ in detail, with the C factor model, incorporating vegetation, coming nearer to the field situation. The main deficiency in all the indices is the weakness in modelling ponding and sedimentation created by the terraces, and therefore the disconnectivity in the landscape. Comparison with field data confirms the variable connectivity in rainstorms, the effects of features such as tracks, and the effect of management actions. Evidence from field mapping during the last two decades indicates that the models probably represent the maximum possible functional connectivity. [ABSTRACT FROM AUTHOR]

Knowledge of the trophic web structure and control mechanisms in reservoirs of the semiarid tropical regions can enable a better understanding and proper management of these aquatic environments. This paper used an ecosystem approach to two Brazilian semiarid reservoirs and evaluated the interactions between cage fish farms and fishing activity. The trophic web models of the reservoirs were elaborated using Ecopath with Ecosim (EwE) software. Over two years, the data were locally obtained, including information on fish farm, fishing activity, and functional groups (phytoplankton, aquatic macrophytes, benthic fauna, and fish). The modeling results indicated that most of the system energy is derived from the detritivory chain, which was more critical than the herbivory chain, with a Detritivory/Herbivory ratio of approximately 3.0 in both reservoirs. The key group of the ecosystem was the piscivorous fish, with Hoplias malabaricus and Cichla monoculus as the species with the greatest trophic impact, especially on fish at the intermediate trophic level. The benthic community and detritus had positive impacts on almost all other components of the trophic web. The reservoirs were considered immature, with low nutrient cycling and a high Total Primary Production/Total Respiration ratio. Systemic stability was deemed low for both reservoirs, which was indicated by the low overhead values. In both reservoirs, the presence of a well-developed detritus chain supports the trophic web and represents a source of stored energy in aquatic systems. The simulations demonstrated a positive relationship between fish farming and fishing activity, with all communities benefiting from the nutrient input from cage fish farms, with a biomass increase of aquatic organisms, either by direct or indirect effects. • This study evaluated the tradeoffs between fisheries and fish farming in net cages, from the aquatic communities perspective. • A food-web model was constructed and the interactions were simulated over time. • There was a positive interaction, with the presence of net cages fish farming favoring the fishing activity. [ABSTRACT FROM AUTHOR]

• Understanding the riparian zone from the watershed river-groundwater transformation. • Revealing the contributions of groundwater to landscape ecological patterns. • Proposing pathways to maintain a healthy landscape ecological pattern. In arid and semiarid areas with scarce precipitation, strong evaporation, and fragile ecosystems, rivers and groundwater interact frequently. Dynamic hydrological changes and solute transport jointly determine the evolution of the landscape in riparian zones, resulting in the formation of a landscape ecological pattern in arid areas that is unique and includes a system of rivers and lakes. In recent decades, unsustainable and mono-purpose grey infrastructure has been implemented in many arid areas, and the effect of river-groundwater interactions on the landscape ecological pattern in riparian zones has often been neglected. These processes have triggered variations in or even the reversal of landscape ecological patterns in these arid areas. This study selected the arid and semiarid basin in northwestern China as the study area. Multiple methods were used to study the evolution of the landscape ecological pattern in the riparian zones driven by typical hydrological processes from the perspective of river-groundwater transformation. Three results were obtained from the analysis: (1) The driving force of the evolution was identified, and the spatial geological heterogeneity, meteorological and hydrological conditions, and river-groundwater interactions played dominant roles in the evolution of the landscape ecological pattern in the riparian zones. (2) Human activities and climate change controlled the direction and intensity of landscape evolution. (3) Pathways for maintaining a healthy landscape ecological pattern in riparian zones and suggestions for identifying the key issues that should be studied in the future were proposed. This paper primarily contributes to a better understanding of landscape ecological patterns in the riparian zone in arid areas from the watershed river-groundwater transformation perspective, thereby promoting integrated watershed management. [ABSTRACT FROM AUTHOR]

• Managed vegetation represents a powerful tool for climate adaptation and mitigation, offering significant potential for positive environmental impact. • In the context of the Arabian Peninsula, managed vegetation has the remarkable capability to cool the surface temperature by over 5°Celsius, particularly during the hottest days of the year. • Achieving sustainability in water management remains a critical challenge that requires careful attention and proactive measures. The growth of vegetation in desert areas is expected to cause considerable changes to the local climate. Compared to bare ground desert, the balance of different processes related to vegetation such as reduced albedo and increased evapotranspiration can either warm up or cool down the surface climate. Quantifying these changes is essential for impact assessments of climate mitigation and adaptation measures, especially in regions increasingly hit by heat waves such as the Arabian Peninsula. In this respect, the analysis of in situ observations is challenging owing to limited data, uneven vegetation distribution, complex terrain, and other confounding factors. Thus, this study, using long-term satellite data at the daily temporal resolution, estimates the impact of vegetation on land surface temperature for several agricultural regions in the Kingdom of Saudi Arabia. Results demonstrate that managed vegetation has a significant cooling effect during the day and particularly during hot weather events, reducing the highest temperatures by > 5 °C. During heat waves, managed vegetation can provide an additional cooling effect of about 3 °C (2 to 4 °C depending on the location). This effect is robustly assessed though a tailored statistical indicator that is suitable for application over complex terrain that are found in the Saudi agricultural sites. However, a situation is identified where the vegetation vigor collapsed and the cooling effect vanished, which was possibly related to issues associated with water management sustainability. Thus, herein, this paper discusses several potential solutions to achieve sustainable irrigation among those that were recently proposed in the scientific literature, such as desalinization from renewable energy and land-use change options that could enhance local precipitation. This study supports the decision-making process of the green initiatives undertaken in the Middle East and similar efforts in other arid regions. [ABSTRACT FROM AUTHOR]

Coastal arid regions face significant challenges in ensuring energy, water, and food security. Given the urgency of meeting these demands, it is necessary to consider innovative solutions that enhance adaptive capacity and sustainable development of coastal zones. Harnessing wave energy has become a potential ocean renewable resource that can provide significant benefits to mitigating coastal vulnerability and climate change. However, most wave energy projects still face different challenges that limit their financing and commercial deployment. This paper aims to evaluate the techno-economic feasibility of 0.5 MW Marine Ecoparks as maritime clusters coupled with wave energy converter, seawater desalination, and marine aquaculture modules to produce the water-energy-food nexus and boost, symbiotically, the viability of the wave energy sector and the blue economy in the arid coastal communities of Baja California, a Mexican Pacific region with a mid-wave energy resource. Based on technical and economic data available in the literature, the cost estimates and the contribution of each coupled module to the Marine Ecopark profitability were carried out and compared against other forms of energy generation using different current and projected 2030 market scenarios. All the cases analyzed show that the Pelamis device generates higher techno-economic performance than the WaveDragon. While individual wave energy devised siting is not profitable, economic scaling in increases maritime clusters' profitability. Optimally selected Pelamis facilities attain capacity factors over 40 % and a Levelized Cost of Energy of 480 $/MWh. The coupled seaweed aquaculture module generates the highest water-energy-food nexus profitability, whereas seawater desalination is not economically viable. All wave energy farms show a decrease in estimated electricity cost by 2030, reaching 198 USD/MWh for the most competitive Pelamis farms. [Display omitted] [ABSTRACT FROM AUTHOR]

• Based on the principles of SPEI, we develop a GDAI. • The relationship between GDAI and AI is closer. • The correlation between GDAI and SPEI is also better. Climate change has increased the risk of drought in both arid and non-arid regions of the globe. Therefore, in order to monitor and evaluate global drought and aridity, based on the principle of standardized precipitation evapotranspiration index (SPEI), this paper selected precipitation and potential evapotranspiration data and used a frequency calculation method to develop a multi-scale global drought aridity index (GDAI) that concurrently considers spatial and temporal variation characteristics: the spatiotemporal standardized precipitation evapotranspiration index. The index was compared with the aridity index (AI) and SPEI. The results showed that the correlation coefficients between GDAI and AI were greater than 0.8 in most areas, and the relationship was closer and could reveal the global aridity and wetness zoning. In addition, the correlation between GDAI and SPEI was also better, which could capture the temporal change characteristics of drought. Moreover, this study also compared the grades of GDAI and SPEI with the actual drought grades in Yunnan from September 2009 to August 2010, and found that GDAI was better than SPEI, and GDAI was the most accurately evaluated at the 3 month time scale, with an accuracy rate of 86.11%. Therefore, this index is more helpful for the assessment and monitoring of global drought and aridity. [ABSTRACT FROM AUTHOR]

• A Decision Support System for flash-flood risk management in the arid areas is designed. • An integrated GIS and Watershed Modelling System is applied for flood flow simulation. • AI and Classic Delphi are employed for smart sustainable management of flash-flood risks. • Flood risk is analysed using Failure Mode and Effects Analysis & Hazard & Operability techniques. This paper presents a novel framework for smart integrated risk management in arid regions. The framework combines flash flood modelling, statistical methods, artificial intelligence (AI), geographic evaluations, risk analysis, and decision-making modules to enhance community resilience. Flash flood is simulated by using Watershed Modelling System (WMS). Statistical methods are also used to trim outlier data from physical systems and climatic data. Furthermore, three AI methods, including Support Vector Machine (SVM), Artificial Neural Network (ANN), and Nearest Neighbours Classification (NNC), are used to predict and classify flash flood occurrences. Geographic Information System (GIS) is also utilised to assess potential risks in vulnerable regions, together with Failure Mode and Effects Analysis (FMEA) and Hazard and Operability Study (HAZOP) methods. The decision-making module employs the Classic Delphi technique to classify the appropriate solutions for flood risk control. The methodology is demonstrated by its application to the real case study of the Khosf region in Iran, which suffers from both drought and severe floods simultaneously, exacerbated by recent climate changes. The results show high Coefficient of determination (R2) scores for the three AI methods, with SVM at 0.88, ANN at 0.79, and NNC at 0.89. FMEA results indicate that over 50% of scenarios are at high flood risk, while HAZOP indicates 30% of scenarios with the same risk rate. Additionally, peak flows of over 24 m3/s are considered flood occurrences that can cause financial damage in all scenarios and risk techniques of the case study. Finally, our research findings indicate a practical decision support system that is compatible with sustainable development concepts and can enhance community resilience in arid regions. [ABSTRACT FROM AUTHOR]

In the digital soil mapping framework, machine learning (ML) algorithms are currently the most popular methods for the spatial prediction of soil properties. The fast developments of easy-to-use software implementations for a large panel of ML algorithms have encouraged comparison studies between algorithms, with the goal of ranking their performances and identifying the best ones among them. However, as no firm conclusions can be drawn about the best ML algorithm to be used in general, this suggests that combining a set of them could be a better approach. Numerous methods have been proposed to do so, most of them relying on a linear weighting of the individual algorithms. However, there are almost as many methods for linearly weighting ML algorithms as there are ML algorithms, thus leaving the problem unsolved. Moreover, these weighting methods are mostly used out-of-the-box, without paying a proper attention to the associated hypotheses. In this paper, we propose to address this issue by setting the problem in a more formal framework. Starting from classical hypotheses, it is shown how the benefit of averaging various ML algorithms can be estimated from their joint performances. Relying afterwards on the most commonly used linear weighting schemes, it is reminded that, as long as the performance metrics are based on mean square errors, the best averaging method is by essence the best linear (unbiased) predictor. Using a more general Bayesian framework, it is also shown that accounting for conditional biases when weighting ML algorithms is a key issue for obtaining improved predictions, and explicit formulas are proposed for that goal. Finally, these theoretical results are illustrated and discussed using a soil data set collected over an arid and semi-arid region in Iran where clay content, calcium carbonate equivalent, soil organic carbon and electrical conductivity were measured in topsoil samples. • Averaging results of several machine learning algorithms is beneficial. • Numerous averaging methods exist but are mostly used out-of-the-box. • The benefit of averaging depends on the correlation between prediction residuals. • Conditional biases are a key issue when averaging machine learning results. • A Bayesian approach provides the best results when conditional biases are present. [ABSTRACT FROM AUTHOR]

Using the ERA-5 monthly reanalysis data and precipitation observations, this paper analyses the interdacal dry-wet transition and its mechanism in the Tarim Basin(TB) during summer. From the long-term perspective(1961–2021), TB is in a trend of "wet in the west and dry in the east". By taking a nine-year moving average of the precipitation(PRE), the research period is divided into three subperiods: P1(1961–1987), P2(1988–2009) and P3(2010−2021). From P1 to P3, the regional averaged Standardized Precipitation Evapotranspiration Index(SPEI) demonstrates an interdecadal turning of "wetting to drying". During P2(1988–2009), the dynamic component of water vapor increases the zonal moisture transport, causing a slight increase in PRE. The potential evapotranspiration(PET) is weakened by the increase in PRE and relative humidity(RH), the decrease in 2-m temperature(T2m) and 10-m wind speed(10UV), resulting in the humidification of the TB. In the P3(2010–2021), the non-linear component of water vapor increases moisture convergence in the western TB, causing a significant increase in PRE. However, the decrease in RH, accompanied by increases in T2m and UV10, results in a rapid increase in PET. The TB gets dry. The South Asian high(SAH) develops southeastward, guiding more water vapor transport from the upstream westerly and the tropical Indian Ocean. The Western Pacific subtropical high(WPSH) extends northwestward, increasing water vapor convergence in the western TB. The main reason for the increased precipitation changes from increased water vapor advection to enhanced water vapor convergence. The differences in PRE formation and T2m amplitude cause the interdecadal change in RH, deriving an interdecadal transition of wet and dry in the TB. Our findings may deepen the understanding of climate change, and provide a scientific support for ecological development, and global climate governance in arid/semi-arid regions. • TB has been presented an interdacal dry-wet transition in summer. • The summer SPEI in the TB is consistent with the interdacadal variations of PET. • The SAH and the WPSH modulate the moisture transport pathways and precipitation formation, influence the dry-wet transition in the TB. [ABSTRACT FROM AUTHOR]

Understanding the origins of groundwater and its movement from mountain to plain during different high intensity rainfall events is critical for conserving water supplies, determining water-use policies and controlling pollution. These factors are also the keys for understanding the dominant processes in hydrological models. In this study, groundwater resources and recharge processes during heavy precipitation were explored by using stable isotope tracers in the hilly area of Taihang Mountain. It was found that the δ2H and δ18O values of precipitation exhibited obvious precipitation amount effect during different precipitation intensity events. The stable isotopic values in groundwater and river water showed significantly varied during the single extreme heavy precipitation and the continuous heavy precipitation events. In the rainy season, precipitation amounts greater than 40 mm/d could effectively recharge the shallow groundwater in the study area. By comparing the spatial isotopic distribution of groundwater, soil water, and river water with precipitation, we showed distinct groundwater recharge patterns in terms of their water resources, timing, and the degree of river water and groundwater interaction during the single extreme heavy precipitation and the continuous heavy precipitation. After the single extreme heavy precipitation, the δ2H and δ18O values of groundwater, soil water, and river water showed stable over time and had the same similar variations, suggested that the groundwater recharge was mainly dominated by precipitation with preferential flow or bypass flow. While after the continuous heavy precipitation, the variation of δ2H and δ18O in all water is consistent with the previous precipitation, which shown a mixing effect of previous enrich precipitation and depleted heavy precipitation, suggested that groundwater source was dominated by a continuous recharge of previous heavier precipitation with translatory flow. The groundwater main recharge mechanism is not constant, but changes with rainfall intensity. The rainfall intensity play an important role in groundwater recharge change affecting runoff process. Overall, this paper presents a new insight to understand the effect of rainfall intensity on hydrological process, which could be used to provide vital information in the semi-humid and semi-arid regions where water resources are critical in climate change adaptation strategies. [Display omitted] • We identified the controls on groundwater recharge during different precipitation intensity events. • Precipitation greater than 40 mm/d could effectively recharge shallow groundwater. • Bypass flow after extreme precipitation produced stream water and groundwater recharge. • Groundwater recharge was by a continuous recharge with translatory flow after the continuous heavy precipitation. [ABSTRACT FROM AUTHOR]