Search

Climate change and human activities have massively impacted the hydrological cycle. Thus, it is of the greatest concern to examine the effect of climate change on water management, especially at the regional level, to understand the possible future shifts in water supply and water-related crises and support regional water management. Fortunately, there is a high degree of ambiguity in determining the effect of climate change on water requirements. In this paper, the statistical downscaling (SDSM) model is applied to simulate the potential impact of climate on crop water requirements (CWR) by downscaling ET0 in the region of Western Maharashtra, India, for the future periods, viz., the 2030s, 2050s, and 2080s, across three meteorological stations (Pune, Rahuri, and Solapur). Four crops, i.e., cotton, soybean, onion, and sugarcane, were selected during the analysis. The Penman-Monteith equation calculates reference crop evapotranspiration (ET0). Furthermore, in conjunction with the crop coefficient (Kc) equation, it calculates crop evapotranspiration (ETc)/CWR. The predictor variables were extracted from the National Centre for Environmental Prediction (NCEP) reanalysis dataset for 1961–2000 and the HadCM3 for 1961–2099 under the H3A2 and H3B2 scenarios. The results indicated by SDSM profound good applicability in downscaling due to satisfactory performance during calibration and validation for all three stations. The projected ET0 indicated an increase in mean annual ET0 compared to the present condition during the 2030s, 2050s, and 2080s. The ET0 would increase for all months (in summer, winter, and pre-monsoon seasons) and decrease from June to September (monsoon season). The estimated future CWR shows variation in the range for cotton (− 0.97 to 2.48%), soybean (− 2.09 to 1.63%), onion (0.49 to 4.62%), and sugarcane (0.05 to 2.86%). The significance of this research lies in its contribution to understanding the potential impacts of climate change at a regional level. This study provides valuable insights into the expected changes in water demand for key crops. The research also manifests implementing an identical methodology for downscaling other environmental parameters using a similar approach. [ABSTRACT FROM AUTHOR]

This paper investigated whether rainfall promotes dilution or increase in nutrient concentrations and which land use indicators are the main predictors of nutrients in intermittent rivers in a large Brazilian semiarid region. The total phosphorus (TP) and total inorganic nitrogen (TIN) were monitored between 2013 and 2018 at 92 river water quality monitoring sites. The monthly rainfall (Rn) was obtained from 575 rain gauges. Pearson's correlation (R) between Rn and nutrient concentration was performed. The correlation patterns were also analysed based on land use data: urban area (%), agricultural field area (%), demographic density (inhabitants/km2), sewer system coverage (%), and reservoir density (reservoir/km2). Backward stepwise regression was performed to identify predictors of nutrient concentrations. The results revealed a marginal effect of rainfall on nutrients when the effects of urbanisation outweigh all other aspects. However, in regions with greater accumulated rainfall and lower reservoir density, the rainfall was related to a linear increase in nutrient concentrations (R > 0.8). Contrastingly, in the basins with less accumulated rainfall and greater inter-basin hydrological disconnection, there was a linear reduction in nutrient concentration (R < − 0.5). In the backward stepwise regression, sewer system coverage and Rn had the greatest influence for TP, and the urban area was the strongest predictor for TIN. Importantly, our results demonstrated that in semiarid rivers in densely populated regions, there is no single pattern of variability in nutrient concentration, on a wide scale of assessment. Therefore, adaptative and decentralised management can be more effective in improving water quality in these regions. [ABSTRACT FROM AUTHOR]

The most robust approach to ecological monitoring and assessment is the use of regionally calibrated indicators. These should be calculated based on collocated biological (response) and physicochemical (stressor) variables and an objective rating and scoring system. In developing countries, a frequent lack of financial and technical resources for monitoring has led to many environmental problems being overlooked, such as the degradation of streams, rivers, and watersheds. In this paper, we propose the Karun Macroinvertebrate Tolerance Index (KMTI) for application to rivers in the Karun River basin, which is the largest watershed in Iran, draining semi-arid mountainous regions. The KMTI is the first biological index specifically developed and calibrated for Iranian water resources. Benthic macroinvertebrates, physical habitat, hydromorphic, and water quality data were collected and measured at 54 sites across four seasons in 2018 and 2019. A total of 101 families of benthic macroinvertebrates belonging to eight classes and 21 orders were identified, and tolerance values were determined for 95 families. The KMTI was found to be most efficient in identifying ecological degradation when data were used from winter samples with a discrimination efficiency (DE) 90% and a four-season mean of 84.3%. Also, the best DE of the water quality classification table based on the KMTI index was equal to 86.9%. [ABSTRACT FROM AUTHOR]

In this paper, Changji, Xinjiang, northwest China, was selected as the study area, and platinum group elements (PGEs) in PM2.5 were quantified by ICP-MS using microwave digestion. The results indicated that the average concentrations (and range) of Rh, Pd, and Pt in PM2.5 were 0.21 (n.d. −1.41) ng/m3, 8.09 (n.d. −59.50) ng/m3, and 0.12 (n.d. −0.83) ng/m3, respectively. The concentration of Pd was significantly higher than Rh and Pt. Moreover, the seasonal variations of Rh and Pd were the same: highest in summer and lower in other seasons. However, the seasonal variation of Pt was opposite to that of Rh and Pd: highest in winter and lower in other seasons. Seasonal differences in emission sources of PGEs and the climatic characteristics of arid regions played important roles in the seasonal changes of PGEs. Rh and Pd had a common source and similar diurnal variation. The major influencing factors were traffic volume and meteorological conditions. The diurnal variation regularity of Pt was different from Rh and Pd. The superimposed effect of vehicle exhaust emissions and coal-fired emissions was the main reason why the diurnal variation of Pt was more complicated than those of Rh and Pd. The diurnal concentration of Pt varied with the seasons. It is caused by seasonal coal combustion and meteorological conditions. [ABSTRACT FROM AUTHOR]

The relationship between human behaviour and vulnerability is interactive, especially in arid and semi-arid regions. This paper analyses vulnerability and human behaviour in the core areas of Qilian Mountains National Park, which is located in Qilian and Sunan counties. We used the vulnerability index and grey correlation degree methods to analyse the data. The results show that from 2005 to 2017, the vulnerability degree in the Qilian Mountain area decreased gradually (Qilian County vulnerability decreased from 0.0357 to − 0.2237, and Sunan County vulnerability decreased from 0.1428 to − 0.4489). In 2017, the degree had reached its lowest value due to central and local government policy (− 0.2237 and − 0.4489). Considering that human behaviour contributed to the vulnerability degree, we find that land use and agricultural development mode, the acceleration of industrialisation and changes in the spatial patterns of human activities, and the development of urbanization and changes in resident identities are the main concepts driving the relationship between human behaviour and vulnerability. The innovative assessment indicators developed in this study can be applied to thoroughly explore the relationship between human behaviour and vulnerability and to find the influencing factors. Under certain conditions, this approach can be applied to vulnerability research in specific countries and regions. [ABSTRACT FROM AUTHOR]

The Qehan Lake Basin (QLB) and its system of lakes are located in a marginal monsoon zone and are extremely sensitive to global climate change. In this paper, using aerial photographs from different periods, in addition to MSS, TM, and ETM images, and combining these with regional topographic maps, we analyze lake area changes from 1958 to 2010 and the relation between Qehan Lake (QL) and climate variability. Our results indicate that there was a relatively high lake level in 1959, when the area and volume of the lake were 118.9 km and 151.9 × 10 m, respectively, but this level was subject to a shrinking trend until 2010, when the lake area was only 28.1 km, and the water volume was 41.1 × 10 m. West Qehan Lake (WQL) has experienced severe water shrinkage and lake level fluctuation. In 1958, WQL was 80.2 km in area and 124.1 × 10 m in volume. However, due to a rapid decrease in precipitation and increases in both temperature and evaporation, it began to dry up in 2002. The WQL Water area decreased by 1.82 km/a, and the lake level declined by 7 m during 1958-2002, so it became an ephemeral lake. [ABSTRACT FROM AUTHOR]

The Chobe River, characterized by an unusual flood pulsing regime and shared between Botswana and Namibia, lies at the heart of the world's largest transfrontier conservation area (the Kavango-Zambezi Transfrontier Conservation Area). Significant ecological changes and vegetation conversions are occurring along its floodplains. Various scenarios for agricultural and urban water use are currently being proposed by the government of Botswana. However, the understanding of the river's annual flow regime and timing of the relative contributions of water from three different sources is relatively poor. In light of past and future climate change and variability, this means that allocating water between ecological flows and economic and domestic uses will become increasingly challenging. We reconstruct the inundation history in this basin to help ease this challenge. This paper presents a spatiotemporal approach to estimate the contribution of water from various sources and the magnitude of changes in the flooding extent in the basin between 1985 and 2010. We used time series analysis of bimonthly NOAA AVHRR and NASA MODIS data and climatologic and hydrologic records to determine the flooding timing and extent. The results indicate that between 12 and 62 % of the basin is flooded on an annual basis and that the spatial extent of the flooding varies throughout the year as a function of the timing of peak discharge in two larger basins. A 30-year trend analysis indicates a consistent decline in the average monthly flooded area in the basin. The results may prove useful in future water utilization feasibility studies, in determining measures for protecting ecological flows and levels, and in ecosystem dynamics studies in the context of current and future climate change and variability. [ABSTRACT FROM AUTHOR]

Desertification is a complex process, characterised not only by a damaged ecology but also by conflict over access to scarce resources and trade-offs between the needs of multiple stakeholders at multiple scales. As such, orthodox approaches to environmental assessment in drylands, which rely solely on ecological expertise, are gradually losing legitimacy and greater attention is being given to integrated and participatory assessment approaches, which draw on multiple sources of knowledge in order to accurately describe complex socioecological processes. Moreover, there is growing recognition that successful management of desertification requires a strategy that can accommodate the multiple and often competing needs of contemporary and future stakeholders. In light of these conceptual advances, this paper highlights seven key criteria that dryland environmental assessments must meet: (1) accurately understand complex socioecological system processes, (2) focus on slow variables, (3) integrate multiple scales of analysis, (4) integrate multiple stakeholder perspectives and values, (5) ensure that future generations are fairly represented, (6) ensure that less powerful stakeholders are fairly represented and (7) integrate local and scientific knowledge. The virtues and challenges of deliberative environmental assessments, a novel subset of participatory environmental assessment approaches which places emphasis on social learning, argumentation and critical reflection, are considered in relation to each of these requirements. We argue that deliberative approaches have the potential to achieve accurate, progressive and integrated assessment of dryland environments. [ABSTRACT FROM AUTHOR]

This paper provides a framework for the managers to devise means to protect, restore, and maintain the remaining bi-species groves for sustainable management of fragile arid land ecosystem. At the moment, there is no information available about the structural and functional ecology of these dwindling remnants. The selection criteria for the classification of the groves are based on understanding the positive association between the two species, Prosopis cineraria and Salvadora oleoides, in terms of spatial pattern and morphological features. It was achieved by highlighting the attributes of the benchmark grove and classification of other groves in reference to it. The results clearly show that positive association in the groves is due to differences in the growth strategies of the two species in terms of above- and belowground biomass allocation and architecture. Most of the groves are in various stages of degradation, and anthropogenic interferences are the major determinant linked with the declining status of the groves. These activities affect the complimentary attributes of the bi-species groves, thus disturbing the characteristic structural features which contributed to the stability of this fragile landscape. [ABSTRACT FROM AUTHOR]

Wind erosion is a phenomenon that is reasonably common in regions where dry winds blow. For the most part, these regions correspond to the dry lands; areas where the soil, generally, is dry and shifting and lacks vegetation for most of the year. The winds are sufficiently strong to lift and move sands and soil particles. The repeated removal of superficial layers by the action of winds can modify the texture of the topsoil, by removing the fine particles and leaving the larger particles. Dust and sandstorm (DSS) is the generic term for a serious environmental phenomenon that involves strong winds that blow a large quantity of dust and fine sand particles away from the ground and carry them over a long distance with significant environmental impacts along the way. In the realm of DSS in Iran country, the people who live in Yazd and Sistan–Baluchestan provinces form a single ecological community due to their geographic proximity and climatic contiguity. The major sources of DSS in the region are believed to be the desert and semidesert areas of the Yazd–Ardakan plain in Yazd province. Both Sistan and Baluchestan are the recipients of this dust. To address the long-range transboundary environmental problem of DSS, a regional cooperation mechanism must be established among the provinces in the region. Yazd–Ardakan plain, with area of about 650,000 ha, is located in the center of Iran, between Yazd and Ardakan cities. The mean annual rainfall is less than 65 mm. Rainfall distribution is a simple modal and more than 70% of it occurs in winter. Plant density varies from 0% to 25%, and Artemisia sieberi is the dominant plant species. The major part of Yazd–Ardakan plain is bare land. According to the recent investigation, more than 20,000-m3 dust with less than 100-μm diameter falls down annually on Yazd city with an area of 7,000 ha. Horizontal visibility is reduced to less than 6 m in stormy days in some parts of Yazd–Ardakan plain. This phenomenon causes car accidents on the main roads of Yazd–Ardakan and can cancel the airplane flights in the stormy days. At present, it is estimated that wind erosion causes more than $6.8 million damages to socioeconomic resources in Yazd plain each year. This paper describes the pattern of occurrence of wind erosion and major contributing factors, summarizes measured rates of wind erosion, outlines the techniques used to mitigate wind erosion hazard, and suggests research priorities. Also, damages of DSS have been estimated and methods for prevention and control are suggested. [ABSTRACT FROM AUTHOR]

There has been increasing concern in highlands of semiarid Turkey that conversion of these systems results in excessive soil erosion, ecosystem degradation, and loss of sustainable resources. An increasing rate of land use/cover changes especially in semiarid mountainous areas has resulted in important effects on physical and ecological processes, causing many regions to undergo accelerated environmental degradation in terms of soil erosion, mass movement and reservoir sedimentation. This paper, therefore, explores the impact of land use changes on land degradation in a linkage to the soil erodibility, RUSLE-K, in Cankiri–Indagi Mountain Pass, Turkey. The characterization of soil erodibility in this ecosystem is important from the standpoint of conserving fragile ecosystems and planning management practices. Five adjacent land uses (cropland, grassland, woodland, plantation, and recreational land) were selected for this research. Analysis of variance showed that soil properties and RUSLE-K statistically changed with land use changes and soils of the recreational land and cropland were more sensitive to water erosion than those of the woodland, grassland, and plantation. This was mainly due to the significant decreases in soil organic matter (SOM) and hydraulic conductivity (HC) in those lands. Additionally, soil samples randomly collected from the depths of 0–10 cm ( D 1) and 10–20 cm ( D 2) with irregular intervals in an area of 1,200 by 4,200 m sufficiently characterized not only the spatial distribution of soil organic matter (SOM), hydraulic conductivity (HC), clay (C), silt (Si), sand (S) and silt plus very fine sand (Si + VFS) but also the spatial distribution of RUSLE-K as an algebraically estimate of these parameters together with field assessment of soil structure to assess the dynamic relationships between soil properties and land use types. In this study, in order to perform the spatial analyses, the mean sampling intervals were 43, 50, 64, 78, 85 m for woodland, plantation, grassland, recreation, and cropland with the sample numbers of 56, 79, 72, 13, and 69, respectively, resulting in an average interval of 64 m for whole study area. Although nugget effect and nugget effect–sill ratio gave an idea about the sampling design adequacy, the better results are undoubtedly likely by both equi-probable spatial sampling and random sampling representative of all land uses. [ABSTRACT FROM AUTHOR]

Shiyang River basin is located in Hexi Corridor, central-west Gansu province, northwest China. It is an area of typical arid to semiarid features. Based on the TM image of Liangzhou oasis and Minqin oasis in 1986 and 2000, this paper calculated and analyzed the changes of percentage and area of land use/cover types, and also have got the transformation matrix of the landscape mosaics. Dynamics of runoff and exploitation of groundwater, the most important factors influencing land use changes were also analyzed. The ratio of utilized water quantity in upper and middle reaches to that in lower reaches has increased largely from less than 2 before 1970 reached up to more than 8 since 1995; groundwater exploitation has developed progressively. As a result of overuse of groundwater, the groundwater table lowering obviously, the lowering rates reached up to 0.6–0.8 m/year in some place. In addition, the cropping patterns in study area were also distributed irrefficiently that if the planting percentage of water-wasting grain crops dropped to 50% in both oases, it could save irrigating water by 1.2×108 m3 in Liangzhou oasis and 0.2×108 m3 in Minqin oasis one year. [ABSTRACT FROM AUTHOR]

Green manure decomposition and nutrient recycling improve soil quality and productivity of different crops, but information on irrigated fruit orchards in the Brazilian semi-arid region is still scarce. Decomposition and nitrogen, phosphate, and potassium release from the cut biomass of three green manure legumes (sunn hemp, pigeon pea and jack bean) placed in litterbags, and spontaneous vegetation grown for 90 days in the rows of a passion fruit orchard were followed for 150 days. Biomasses decreased exponentially, reaching 12 (sunn hemp) to 25% (jack beans and spontaneous vegetation) after 150 days. K was rapidly released (< 21 and 4% of the original content remaining after 7 and 150 days, respectively), contrasting with more than half of the P and one third of the N remaining after 150 days. The amounts released were more influenced by the amounts of biomass produced (sunn hemp, 1583); (Jack bean 5152 kg ha-1); (Pigeon pea 822 kg ha-1); (Spontaneous plants 3175 kg ha-1); (spontaneous legumes 744 kg ha-1) than by variation in decomposition proportions among species. N release represented a liquid input to the soil, since more than 80% of the green manure and spontaneous vegetation contents came from N2-symbiotic fixation. Therefore, green manure is an effective technique to incorporate N and recycle K and P in irrigated orchards in the Brazilian semi-arid region. [ABSTRACT FROM AUTHOR]

The intensity and frequency of diverse hydro-meteorological disasters viz., extreme droughts, severe floods, and cyclones have increasing trends due to unsustainable management of land and water resources, coupled with increasing industrialization, urbanization and climate change. This study focuses on the forecasting of drought using selected Artificial Neural Network (ANN)-based models to enable decision-makers to improve regional water management plans and disaster mitigation/reduction plans. Four ANN models were developed in this study, viz., one conventional ANN model and three hybrid ANN models: (a) Wavelet based-ANN (WANN), (b) Bootstrap based-ANN (BANN), and (c) Wavelet-Bootstrap based-ANN (WBANN). The Standardized Precipitation Evapotranspiration Index (SPEI), the best drought index identified for the study area, was used as a variable for drought forecasting. Three drought indices, such as SPEI-3, SPEI-6 and SPEI-12 respectively representing "short-term", "intermediate-term", and "long-term" drought conditions, were forecasted for 1-month to 3-month lead times for six weather stations over the study area. Both statistical and graphical indicators were considered to assess the performance of the developed models. For the hybrid wavelet model, the performance was evaluated for different vanishing moments of Daubechies wavelets and decomposition levels. The best-performing bootstrap-based model was further used for analysing the uncertainty associated with different drought forecasts. Among the models developed for drought forecasting for 1 to 3 months, the performances of the WANN and WBANN models are superior to the simple ANN and BANN models for the SPEI-3, SPEI-6, and SPEI-12 up to the 3-month lead time. The performance of the WANN and WBANN models is the best for SPEI-12 (MAE = 0.091-0.347, NSE = 0.873-0.982) followed by SPEI-6 (MAE = 0.258-0.593; NSE = 0.487-0.848) and SPEI-3 (MAE = 0.332-0.787, NSE = 0.196-0.825) for all the stations up to 3-month lead time. This finding is supported by the WBANN analyze uncertainties as narrower band width for SPEI-12 (0.240-0.898) as compared to SPEI-6 (0.402-1.62) and SPEI-3 (0.474-2.304). Therefore, the WBANN model is recommended for the early warning of drought events as it facilitates the uncertainty analysis of drought forecasting results. [ABSTRACT FROM AUTHOR]

Semiarid regions are often affected by water scarcity and poor water quality. Seasonal changes in precipitation and drought events increase the pressure of use on water bodies and their pollution. In Central Northern Namibia, a high seasonal intra- and inter-annual variability of precipitation caused a 5-year lasting drought period. In the semiarid region, ephemeral channels and water pans represent the main water source, besides the institutionalized water supply. No systematic analysis of its quality has been conducted so far. The states of the surface waters at the end of the dry season in 2017 and the end of the rainy seasons in 2018 and 2019 were characterized by the analysis of physical–chemical parameters, focusing on usability. The first results show coarse contamination of the waters, which results in high turbidity values. Salt concentrations, such as Ca2+ and Na+, greatly increased due to evaporation. Al is present in high concentrations in solid and liquid phases, which indicates direct anthropogenic pollution. Spatial differences are evident in the study area and based on the precipitation gradient, land use, and population density. The waters cannot be used as drinking water without prior treatment. [ABSTRACT FROM AUTHOR]

In semi-arid regions, interactions between biophysical and socio-economic variables are complex. Such interactions and their respective variables significantly alter land use and land cover, degrade landscape's structure, and impede the efficacy of the adopted land management interventions. This scenario is particularly prevalent in communal land tenure system or areas managed by a hybrid of traditional and state led institutions. Hence, this study sought to investigate the impacts of land use and land cover changes (LULCCs) on land degradation (LD) under communal rural districts, and the key drivers of habitat fragmentation in the Greater Sekhukhune District Municipality (GSDM), South Africa. The study used the wet and dry season multi-temporal remotely sensed image data, key-informant interviews, and workshop with tribal council to determine the major drivers of LULCC and LD. Results revealed that mines and quarries, subsistence and commercial cultivation, and thicket/dense bush LULCs declined significantly during the study period. These LULCs mostly declined in wet season, with loss in vegetation cover highly prevalent. Specifically, the highest conversions were from shrub/grassland to bare soil, thicket/dense bush to shrub/grassland, and shrub/grassland to residential, respectively. Generally, LULCC affected vegetation productivity within the study area, with increased negative NDVI values observed during the dry season. The findings from key informants and the tribal council workshop emphasized that soil erosion, abandonment of cropland, and injudicious land use (i.e. overgrazing and consequent bush encroachment) have severely degraded the land. The study also established that the degrading land can be attributed to the weakening local communal land management system, particularly the weakening tribal councils. The study recommends an urgent need for collaborative (i.e. government, tribal authorities, and land users) land management through designing relevant multi-stakeholder LD mitigation measures. [ABSTRACT FROM AUTHOR]

It is critical to understand the risk of element pollution in soils by evaluating their background levels. Phosphorus (P) content in agricultural soils needs to be assessed from agronomic and environmental standpoints. The current study intended to calculate the background levels of available and total P in soils. To achieve this goal, 50 sites without human activities were selected. Soils were sampled from the surface and subsurface of each site (100 soil samples). The available P forms in soils were extracted using the water-extractable P (WEP), calcium chloride-extractable P (CCEP), and Olsen-extractable P (OEP) methods. The first two extractants are being used to evaluate P leaching from soils, while the last one is being used as an agronomic indicator. The methods used to calculate background levels were the iterative 2-δ technique (2-δ) and the calculated distribution function (CDF). Results showed that the upper limits of background levels using 2-δ method were 1.45, 0.92, 8.12, and 424.4 mg kg−1 for WEP, CCEP, OEP, and total P, respectively. Also, the upper limits of background levels using CDF method were 1.42, 1.15, 12.09, and 447.6 mg kg−1, for WEP, CCEP, OEP, and total P, respectively. It can be concluded that using these background levels, which for the first time were calculated for P, would enable us to have an accurate examination of P excess as a result of human activities. [ABSTRACT FROM AUTHOR]

Barren lands are being transformed into agricultural fields with the growing demand for agriculture-based products. Hence, monitoring these regions for better planning and management is crucial. Surveying with high-resolution RS (remote sensing) satellites like Worldview-2 provides a faster and cheaper solution than conventional surveys. In the study, the arid region comprising cropland and barrenlands are efficiently and autonomously delineated using its spectral and textural properties using state-of-the-art random forest (RF) ensemble classifiers. The textural information window size is optimized and at a GLCM (gray-level co-occurrence matrix) window size of 13, a stable trend in classification accuracy was observed. A further rise in window sizes did not improve the classification accuracy; beyond GLCM 19, a decline in accuracy was observed. Comparing GLCM-13 RF with the no-GLCM RF classifier, the GLCM-based classifiers performed better; thus, the textural information assisted in removing isolated crop-classified outputs that are falsely predicted pixel groups. Still, it also obscured information about barren lands present within croplands. Delineation accuracy was 93.8 % for the no-GLCM RF classifier, whereas, for the GLCM-13 RF classifier, an accuracy of 97.3 % was observed. Thus, overall, a 3.5 % improvement in accuracy was observed while using the GLCM RF classifier with window size 13. The textural information with proper calibration over high-spatial resolution datasets improves crop delineation in the present study. Henceforth, a more accurate cropland identification will provide a better estimate of the actual cropland area in such an arid region, which will assist in formulating a better resource management policy. [ABSTRACT FROM AUTHOR]

In the semiarid Bulal transboundary catchment of southern Ethiopia, groundwater is the only reliable drought-resilient water source. The central and southern parts of the catchment are dominantly overlain by the transboundary aquifers of the Bulal basalts, while the basement rocks outcrop in the eastern part. This study uses an integrated geographic information system (GIS), remote sensing (RS), and analytical hierarchal process (AHP) to identify and delineate the groundwater potential zones of the semiarid Bulal catchment within the Ethiopian territory. Based on their relative importance to groundwater occurrence and movement, ten input parameters were chosen. According to Saaty's AHP approach, the input themes and each of their distinct features were given normalized weights. A composite groundwater potential zone index (GWPZI) map was generated by integrating all the input layers employing the GIS-overlay analysis technique. The map was validated using the yield of wells from the catchment. The GWPZI map depicts four groundwater potential zones: high (representing 27% of the total area), moderate (20%), low (28%), and very low (25%). The geological feature has the greatest influence on the distribution of groundwater potential. Areas with high potential are mainly overlain by the Bulal basaltic flow, while low groundwater potential zones are in the regolith over the basement rocks. Unlike conventional methods, our novel approach is effective in identifying relatively shallow GWPZs throughout the catchment, and it can be applied in similar semiarid regions. The GWPZI map serves as a quick guide for effectively planning, managing, and developing the catchment's groundwater resources. [ABSTRACT FROM AUTHOR]

Coastal aquifer is a fragile environment due to the interaction of groundwater with seawater, especially in arid environments. Groundwater along Kuwait's Bay is polluted due to discharge of waste from desalination plants, power plants, and other anthropogenic activities. Earlier studies on submarine groundwater discharge in Kuwait's Bay region have reported the transfer of nutrient flux from the groundwater to Kuwait's Bay. The current study focused on nitrate sources and processes governing their distribution in groundwater samples collected from the southern part of Kuwait's Bay. The concentration of nitrate in the samples ranged from 22.7 to 803.9 mg/L. Higher values were noted in the samples collected inland and a few samples adjacent to the Bay. Spearman's correlation analysis of the data indicated that NO3− has a strong positive correlation with SO42− and moderate positive correlation with Na + , TDS/EC. The PCA analysis and factor scores revealed the different sources for groundwater nitrate contamination as follows: leakage of sewer lines in the urban region has led to the infiltration of contaminated sewage, high saline environment due to seawater intrusion, chemical weathering, and influence of denitrifying bacteria. The health risk has resulted due to the NO3− concentration being above the standard limit for adults. Furthermore, the nitrate concentration was higher in the region adjoining the landfills. In addition, the discharge of groundwater with higher nitrate to the adjacent open water in the Bay may lead to eutrophication. Hence, proper management strategies are to be adopted to control the nitrate pollution in groundwater. [ABSTRACT FROM AUTHOR]

The shortage of freshwater and salinization are considered two major development problems in arid and semi-arid regions. The growth of population, development of industry and agriculture, and climate change cause over-extraction of groundwater resources; consequently, the quality and quantity of groundwater decreased, especially in the arid and semi-arid areas. The present study investigates the reasons for salinization of the Kashan aquifer. In this study, 53 observation wells located in the aquifer were examined for qualitative study. A total of 80 samples were collected from selected wells over a period of 5 years (2005–2009) and analyzed for 9 chemical parameters (electrical conductivity (EC), pH, total dissolved solids (TDS), sodium (Na+), potassium (K+), calcium(Ca2+, magnesium (Mg2+), chlorine (Cl−), and bicarbonate (HCO−3)). Groundwater table study shows that the direction of groundwater flow throughout the aquifer is often from the west to the east of the aquifer, except for the northeastern part of the aquifer, where a backflow from the northeast (salt lake) into the aquifer is visible. Results of ion analysis in different areas of the aquifer indicate the occurrence of upconing phenomenon in the center and south regions and the occurrence of saline water intrusion phenomenon in northeast regions. To simulate the condition of the Kashan aquifer for the next 50 years, a model of the quantity and quality of the aquifer was developed using the SEAWAT code. According to the results, the salinization of the Kashan plain aquifer should occur due to two main reasons: irregular groundwater extraction and upconing phenomenon and the intrusion of saline water from the salt lake towards the aquifer. The Kashan aquifer salinization forecast results show that the continuation of the current pumping activities for the next 50 years should increase the numbers of wells affected by salinity. Considering the critical situation of the Kashan aquifer and the existing serious threats, serious decisions and measures for the proper management of groundwater and aquifer protection are vital. [ABSTRACT FROM AUTHOR]

Information about the spatiotemporal variability of soil salinity is important for managing salinization in gravel–sand mulched fields. We used inverse distance weighting (IDW) and cokriging to model the spatial variability of soil salinity from 2013 to 2016 and used an autoregressive moving-average (ARMA) model time series to analyze the temporal variability. The objectives of this paper are (a) to compare IDW and cokriging for predicting salinity in deep soil layers from surface data, thus finding a more appropriate method to model the spatial variability of soil salinity, and, using ARMA time series, (b) to identify one or a few sampling points, where soil salt content is the most temporally stable, to increase sampling efficiency or decrease cost and to estimate the overall soil salt content of a field. The IDW interpolation was more accurate than cokriging when using surface salt content to estimate the content in deep layers; so, we used IDW to interpolate the data and draw spatial distribution maps of salt content. Salinity in the 0–10 cm layer gradually decreased with the amount of gravel–sand mulching, from 1.02 to 0.7 g/kg over four years, and increased with depth. ARMA was accurate when using sample dates to predict soil salinity in the time series, and the model was more stable. The stability of the salt spatial patterns over time and along the soil profile allowed us to identify a location representative of the field-mean salt content, with mean relative error ranging between 0.56 and 2.19%. The monitoring of soil salt from a few observations is thus a valuable tool for practitioners and will aid the management of soil salt in gravel–sand-mulched fields in arid regions, with a range of potential applications beyond the framework of monitoring salinity. [ABSTRACT FROM AUTHOR]

Biskra region currently shows signs of stress and a high risk of groundwater contamination by various chemicals and pesticides. For this purpose, a modified integrated susceptibility index (SI) is coupled with remote sensing (RS) and WetSpass model to assess the sensitivity of the groundwater and the risk of pollution in the most exploited aquifer (Quaternary aquifer) in the study area. The results of the modified SI model show that a major part of the aquifer is at risk of contamination if the farmers do not implement good agricultural practices. Four sensitivity levels are considered, reflecting a vulnerability rating that ranges from low to very high. The very high category is observed in the agricultural areas with an estimated pollution index ranging from 84 to 90.57, while a large part of the aquifer shows a high vulnerability to contamination (64 < SI ≤ 84). This category is found in areas characterized by the dominance of bare soil. In urban areas, the vulnerability level decreases to low category (37 < SI ≤ 45). However, the area of forests is classified as moderate to vulnerability (45 < SI ≤ 64). The different statistical and GIS methods confirm the reliability of the obtained SI map. The combination of the SI method with WetSpass model and RS can give a reliable map to help and assist the authorities and decision-makers in groundwater resources planning and the implementation of monitoring programs and networks to control the quality of groundwater in arid environments. [ABSTRACT FROM AUTHOR]

We investigated soil characteristics and heavy metal content changes in 12 inactive dumpsites in humid and semiarid tropical climates in Northeast Brazil. The metals Cu, Cr, Ni, Pb and Zn in soil samples were determined by atomic absorption spectrophotometry. Other parameters measured include pH, electric conductivity, soil texture, soil organic carbon, total porosity and available P. The soil contents of sand, clay, soil organic carbon, available P and heavy metals, and soil bulk density, total porosity and pH were efficient indicators of soil degradation. We found no influence of current use, soil class or climate on the soil response. The mean concentrations of heavy metals in the dumpsite soils followed the order Zn (49.96 mg kg−1) > Cu (38.48 mg kg−1) > Pb (24.64 mg kg−1) > Cr (21.94 mg kg−1) > Ni (7.77 mg kg−1). They were 6- to 36-fold higher than the background values for the region and were above the Brazilian guideline values for metals. The four dumpsite soils that showed simultaneous contamination with two or more heavy metals were located in the semiarid region. This challenges the assumption that soil impacts in the semiarid region are minimal due to lower leaching and high evaporation. Soil changes increase with time under activity, size and decommission time of the dumpsite. These data are important for local authorities to establish more effective targeting policies for closure of dumps and control of the spread of contaminants in areas impacted by the disposal of municipal waste. [ABSTRACT FROM AUTHOR]

The phenomenon of climate change is the biggest environmental challenge in the world. Climate is a determinant factor in species distribution, and climate change will affect the species' abilities to occupy geographic regions. In this study which was conducted in May of 2019, spatio-temporal changes in potential habitats of Gymnocarpus decander were assessed using the MRI-CGCM3 climate change model for RCP2.6 and RCP8.5 scenarios for the near future (2041–2061) and far future (2061–2080) periods for this purpose, climatic variables of 24 synoptic stations across a case study, bio-climatic data and vegetation cover maps of G. decander were used. First, using the factor analysis process, the dimensions of the station-observed climatic variables were reduced to five factors with a total variance of 88.3%. Then, the region was divided into five homogeneous climatic regions using partitional clustering analysis. In this study by using the logistic regression modeling technique, the probability of the presence of the desired species for two groups of independent variables including climatic factors and bioclimatic variables in each of the groups was modeled. The results showed that the best models for determining the potential habitats of G. decander are logistic regression models in groups with independent bioclimatic variables. According to the results obtained from both scenarios, the habitats of G. decander species will decrease in the future. In the most optimistic case, about 8% of G. decander habitats will be lost by 2060 and about 12% by 2080. According to modeling results, currently, 48.2% total area of the region under study has a high potential for the presence of G. decander. Also, results indicate that region number 4 in this study with an altitude range of about 800–1250 m, 16 °C average temperature in the growing season and annual precipitation around 150–170 mm is the major habitat for G. decander. According to climate change under the RCP2.6 scenario, the area of potential habitats of G. decander will decrease to 40% in the near future and 36.4% in the far future; and according to climate change under the RCP8.5 scenario, the area of potential habitats of G. decander will decrease to 23.9% in the near future and 32.5% in the far future. In the far future, because of the increase in total precipitation, some of the lost potential habitats during the near future will be suitable again for G. decander. Due to its stability in harsh environmental conditions, G. decander appears as a type-forming species in a wide range of natural habitats in the study area and is therefore important in terms of soil protection and forage production. [ABSTRACT FROM AUTHOR]

Fires can pose a threat to forest ecosystems when those ecosystems are not fire-adapted or when forest community conditions make them vulnerable to wildfires. Thus, investigating fire-prone environmental conditions is urgently needed to create action plans that preserve these ecosystems. In this sense, climate variables can determine the environmental conditions favorable for forest fires. Our study confirms that vapor pressure deficit (VPD) is an essential climate indicator for forest fires, as it is related to maximum temperatures and low humidity, representing the stress conditions for vegetation prone to fires. This study explores the extent to which ENSO phases can modulate climatic conditions that lead to high VPD over Guanajuato, a semi-arid region in central Mexico, during the dry season (March–April-May). Using fire occurrence data from MODIS (2000–2019) and Landsat 5 (1998–1999), we developed a climatic probability model for the occurrence of forest fires using VPD estimated from ERA5 reanalysis for each ENSO phase. We found that VPD and the occurrence of forest fires were higher during El Niño than under Neutral and La Niña years, with a higher risk of forest fire occurrence in Guanajuato's southern region. This study concludes that it is necessary to implement regional and local fire management plans, especially where the largest number of natural protected areas is located. [ABSTRACT FROM AUTHOR]

Many toxicological studies revealed the deleterious effects on human health induced by trace metals in ambient particulate matter (PM). This study reports the season-dependent water-soluble and total metal mass in PM10 collected simultaneously over five microenvironments in a semi-arid urban region, Ahmedabad, located in western India. The mineral dust fraction in PM10 over Bapunagar, Narol, Paldi, Income Tax, and Science City was estimated to be around 39, 45, 47, 44, and 31% during summer (May–June 2017) and 24, 55, 28, 27, and 28% during winter (December 2017–January 2018), respectively, corroborating mineral dust is perennial in the air over Ahmedabad. The PM2.5/PM10 mass ratios over all the sites were higher during winter (40–60%) as compared to those during summer (30–40%), indicating the contribution from the anthropogenic sources to PM mass. Among the metals monitored, the estimated considerable amount of high masses of Zn, Cu, Ni, Cd, and Sb during winter can be ascribed to the anthropogenic inputs based on the estimated enrichment factors (EF). In contrast to the crustal source, these metals might have been possibly emitted from several other man-made sources, which were found to be more water-soluble during both seasons. As per the standards of incremental excess lifetime cancer risk (IELCR), it is estimated that the atmospheric mass concentration of carcinogenic metals such as Cr, Co, and As was higher in all these sites, whereas the metals such as Pb, Ni, and Cd are also found over the industrial site (Narol) in addition to the above-said metals. Notably, people are highly susceptible to these metals, leading to the potential risk of cancer during both seasons. [ABSTRACT FROM AUTHOR]

There is a close relationship between human health and the quality of the ration used by domestic animals. Also, molds, like genus of Aspergillus, infect animal and human food products with dangerous toxic substances, i.e., aflatoxins that are causing primary and secondary mycotoxicosis in animals and human. The aim of this study was to compare fungal species that contaminated and produced aflatoxin in livestock and poultry feed in Gonabad that is a semi-arid city in northeast of Iran. Sampling was randomly performed three times from two livestock feed mills and two poultry feed mills during summer and autumn. Samples were cultured in two forms of solid and suspension in Sabouraud dextrose agar with chloramphenicol medium (SC) for 5 days in 28 °C. Microscopic diagnostic test and also molecular diagnostic test were used to determine fungal species in culture based on β-tubulin gene sequencing. A total of 27.25% and 31.7% of two livestock feed and two poultry feed samples were contaminated with Aspergillus, respectively. Aspergillus flavus (n = 4), Aspergillus Fumigatus (n = 2), Aspergillus versicolor (n = 2), Aspergillus niger (n = 2), Aspergillus parasiticus (n = 1), Aspergillus ochraceus (n = 1), and Aspergillus terreus (n = 1) were detected by molecular PCR test. The rate of contamination to genus of Aspergillus in autumn was higher than summer (P value = 0.008). Poultry feed sample showed more contamination to Aspergillus species compared with livestock feed. [ABSTRACT FROM AUTHOR]

Impervious surfaces are a significant issue of both urbanization and environmental assessment. However, it is a problem to classify impervious surface (IS) and soil areas as separate classes in land cover classification. The objectives of this study are to obtain impervious surface, vegetation, and soil areas clearly of an urban complex with a semi-arid climate and to better determine the relationships of IS, vegetation, and soil areas with land surface temperatures (LSTs). For this purpose, IS, vegetation, and soil areas in a semi-arid city of Turkey-Kayseri city were identified by using Normalized Difference Anthropogenic Impervious Surface Index (NDAISI) data and support vector machine (SVM) method together in the classification of different areas. Landsat 5, 7, and 8 satellite images of 1987, 2000, and 2013 were used, respectively, in this study. Afterward, the effects of these areas on LSTs were analyzed. Regression analysis was used to determine the relationships between land cover areas and surface temperatures. To better demonstrate these relationships, besides common pixel-based and classical regional-based approaches, a new density-based regional analysis approach was proposed. This study is an innovative one in terms of detecting IS and indicating relationships between land cover areas and surface temperatures in semi-arid regions. Another innovation of the study is related to the results produced. The results showed that decreasing LST values were observed with increasing IS and vegetation cover values and increasing LST values were observed with increasing soil areas. The present findings may provide significant contributions to the literature and will facilitate the development of urban planning strategies in semi-arid regions. [ABSTRACT FROM AUTHOR]

Oases support 90% of the province's inhabitants and produce more than 95% of the social wealth in Xinjiang Province of China. Oases' dependency on water availability from mountainous regions plays a critical factor in the sustainability of agricultural practices and oasis expansion. In this study, we have chosen the Cele Oasis located in the south rim of the Taklimakan Desert, typical of oases in the region, as a case study to examine water availability. With over 97% of Cele's economy tied to agriculture, unfettered expansion of the oasis into the desert has raised concern on water availability. A spatial and temporal analysis of water availability is performed using newly available data to determine whether agricultural production within the Cele Oasis has overexploited available water resources or if feasible expansion of agricultural production is feasible beyond its current boundary. Transferability of the methodology for assessing water availability spatially and temporally will be beneficial to other oases in the arid region that face similar concerns. [ABSTRACT FROM AUTHOR]

Accurate assessment of deep percolation (potential groundwater recharge) under different field crops is essential for sustainable management of scarce water resources and proper planning of crop rotation in irrigated, semi-arid regions of the world. The potential recharge from commonly grown field crops in semi-arid Indo-Gangetic Plain (IGP) of India was estimated using HYDRUS-1D model, where, irrigation, evapotranspiration, and soil moisture dynamics were simulated. Simultaneously, net groundwater use by different cropping patterns was also calculated. Among the hydraulic parameters, n was found most sensitive for water percolation. During rainy season, 293.8 and 159.1 mm water was percolated below the root zone of cotton and soybean, respectively, which accounted for 39.4 and 32.9% of the water input. During winter season, 66.8 and 30.3 mm water was percolated below the root zone of winter maize and mustard, respectively, accounting for 20.5 and 10.6% of added water. It was observed that net groundwater use was positive for cotton, soybean, and summer maize with the values of 168.8, 159.1, and 18.0 mm year−1, respectively, and negative for rice, wheat, winter maize, and mustard. For the eight most important cropping patterns of semi-arid IGP, the net groundwater use was negative and varied between − 4.4 mm year−1 for cotton-maize and −423 mm year−1 for rice-wheat. With these cropping patterns, the overall rate of decline of groundwater was 231 mm year−1. It was found that maize-wheat and soybean-wheat cropping patterns consume much less water than rice-wheat cropping pattern and therefore are suitable to arrest the declining trend of groundwater in semi-arid IGP of India. [ABSTRACT FROM AUTHOR]

In arid environmental regions, such as the Kingdom of Saudi Arabia (KSA), each and every drop of groundwater needs to be efficiently utilized to meet growing water demands. Ground water treatment plants (WTPs) are regularly being monitored by the municipalities to ensure safe water supply. However, analyzing large data to assess the performance of a WTP has always been a daunting task for plant's management. Most of existing performance assessment frameworks were developed for surface WTPs. In this research, an assessment framework using performance-based water quality indices ( P ) is developed to facilitate senior management of ground WTPs for effective decision-making. The framework is also implemented on a case study of Buraydah, Qassim, Saudi Arabia. Five most important water quality parameters (WQPs) have been selected to assess the performance of different components of the WTP, including raw water, pre-treatment, ultrafiltration, sand filtration, reverse osmosis, and final product. Depending on the relative importance of WQPs for a specific treatment process, different weighting schemes have been developed for each treatment process using fuzzy analytical hierarchical process (FAHP) to address the possible uncertainties in data and imprecision in expert opinion. Subsequently, fuzzy weighted sum method (FWSM) is employed to develop aggregated P for assessing average monthly performance during the year 2016. Study results show that all the units consistently performed 'high,' and the plant is meeting drinking water quality standards throughout the year. Hypothetical scenario analysis revealed robustness of the developed framework by showing lacking performance in case failure of different units. [ABSTRACT FROM AUTHOR]

The aim of this study was to produce a land productivity dynamic map of a degraded catchment located in dryland ecosystem via a land degradation assessment using three indicators, namely land use, land productivity, and soil organic carbon density. The study was conducted in the Mogan Catchment, Turkey, between 2000 and 2010. The study embraced the current trend for assessing ecosystem services over wide areas. For this purpose, satellite images were used to determine changes in land use and vegetation density. In addition, a total of 834 soil samples were collected from the surface soil in 2000 and 2010 to assess the soil organic carbon density. In more than 37% of the catchment area of approx. 37,100 ha, land productivity had declined, while about 43% of the catchment showed early signs of decline. Analysis of long-term changes and the conversion of levels of vegetative or standing biomass into land productivity dynamics (LPD) is only the first step. Current land management practices are contributing to serious, widespread land degradation, with only a very small area of the catchment showing a stable or increasing LPD for the period from 2000 to 2010. The implementation of land management policies and practices in order to achieve sustainable land management are urgently required. [ABSTRACT FROM AUTHOR]

Understanding the responses of vegetation characteristics and soil properties to grazing disturbance is useful for grassland ecosystem restoration and management in semiarid areas. Here, we examined the effects of long-term grazing on vegetation characteristics, soil properties, and their relationships across four grassland types (meadow, Stipa steppe, scattered tree grassland, and sandy grassland) in the Horqin grassland, northern China. Our results showed that grazing greatly decreased vegetation cover, aboveground plant biomass, and root biomass in all four grassland types. Plant cover and aboveground biomass of perennials were decreased by grazing in all four grasslands, whereas grazing increased the cover and biomass of shrubs in Stipa steppe and of annuals in scattered tree grassland. Grazing decreased soil carbon and nitrogen content in Stipa steppe and scattered tree grassland, whereas soil bulk density showed the opposite trend. Long-term grazing significantly decreased soil pH and electrical conductivity (EC) in annual-dominated sandy grassland. Soil moisture in fenced and grazed grasslands decreased in the following order of meadow, Stipa steppe, scattered tree grassland, and sandy grassland. Correlation analyses showed that aboveground plant biomass was significantly positively associated with the soil carbon and nitrogen content in grazed and fenced grasslands. Species richness was significantly positively correlated with soil bulk density, moisture, EC, and pH in fenced grasslands, but no relationship was detected in grazed grasslands. These results suggest that the soil carbon and nitrogen content significantly maintains ecosystem function in both fenced and grazed grasslands. However, grazing may eliminate the association of species richness with soil properties in semiarid grasslands. [ABSTRACT FROM AUTHOR]

Understanding the responses of vegetation characteristics and soil properties to grazing disturbance is useful for grassland ecosystem restoration and management in semiarid areas. Here, we examined the effects of long-term grazing on vegetation characteristics, soil properties, and their relationships across four grassland types (meadow, Stipa steppe, scattered tree grassland, and sandy grassland) in the Horqin grassland, northern China. Our results showed that grazing greatly decreased vegetation cover, aboveground plant biomass, and root biomass in all four grassland types. Plant cover and aboveground biomass of perennials were decreased by grazing in all four grasslands, whereas grazing increased the cover and biomass of shrubs in Stipa steppe and of annuals in scattered tree grassland. Grazing decreased soil carbon and nitrogen content in Stipa steppe and scattered tree grassland, whereas soil bulk density showed the opposite trend. Long-term grazing significantly decreased soil pH and electrical conductivity (EC) in annual-dominated sandy grassland. Soil moisture in fenced and grazed grasslands decreased in the following order of meadow, Stipa steppe, scattered tree grassland, and sandy grassland. Correlation analyses showed that aboveground plant biomass was significantly positively associated with the soil carbon and nitrogen content in grazed and fenced grasslands. Species richness was significantly positively correlated with soil bulk density, moisture, EC, and pH in fenced grasslands, but no relationship was detected in grazed grasslands. These results suggest that the soil carbon and nitrogen content significantly maintains ecosystem function in both fenced and grazed grasslands. However, grazing may eliminate the association of species richness with soil properties in semiarid grasslands. [ABSTRACT FROM AUTHOR]

Assessment of groundwater quality is of utmost significance in arid regions like Saudi Arabia where the lack of present-day recharge and high evaporation rates coupled with increasing groundwater withdrawal may restrict its usage for domestic or agricultural purposes. In the present study, groundwater samples collected from agricultural farms in Hail (15 samples), Al Jawf (15 samples), and Tabuk (30 samples) regions were analyzed for their major ion concentration. The objective of the study was to determine the groundwater facies, the main hydrochemical process governing the groundwater chemistry, the saturation index with respect to the principal mineral phases, and the suitability of the groundwater for irrigational use. The groundwater samples fall within the Ca-Cl type, mixed Ca-Mg-Cl type, and Na-Cl type. Evaporation and reverse ion exchange appear to be the major processes controlling the groundwater chemistry though reverse ion exchange process is the more dominating factor. The various ionic relationships confirmed the reverse ion exchange process where the Ca and Mg in the aquifer matrix have been replaced by Na at favorable exchange sites. This phenomenon has accounted for the dominance of Ca and Mg ions over Na ion at all the sites. The process of reverse ion exchange was further substantiated by the use of modified Piper diagram (Chadha's classification) and the chloro-alkaline indices. Evaporation as a result of extreme aridity has resulted in the groundwater being oversaturated with aragonite/calcite and dolomite as revealed by the saturation indices. The groundwater samples were classified as safe (less than 10) in terms of sodium adsorption ratio (SAR) values, good (less than 1.25) in terms of residual sodium carbonate (RSC) values, and safe to moderate (between 0 and 3) in terms of Mg hazard for irrigation purposes. Though the high salinity groundwater in the three regions coupled with low SAR values are good for the soil structure, it can have a negative impact on the crop production by adversely affecting the crop physiology. Cultivation of high-salinity-resistant varieties of crops is recommended for maximum agricultural productivity. [ABSTRACT FROM AUTHOR]

Determining heavy metal background concentrations in soils is fundamental in order to support the monitoring of potentially contaminated areas. This is particularly important to areas submitted to high environmental impact where an intensive and local monitoring is required. To this end, the aim of this study was to establish background concentrations and quality reference values (QRVs) for the heavy metals Cd, Cr, Cu, Fe, Mn, Ni, Pb, Zn, As, and Hg in an environmentally impacted watershed from Brazil. Geochemical associations among Fe, Mn, and trace elements were also assessed to provide an alternative tool for establishing background concentrations. A total of one hundred and four samples comprised twenty-six composite soil samples from areas of native forest or minimal anthropic influence. Samples were digested (USEPA method 3051A), and the metals were determined by ICP-OES, except for As and Hg measured by atomic absorption spectrophotometer. Background concentrations of heavy metals in soils had the following decreasing order: Fe > Mn > Zn > Cr > Pb > Ni > Cu > As > Cd > Hg. These values were usually lower than those observed in the international and national literature. The QRVs for Ipojuca watershed followed the order (mg kg) Fe (13,020.40) > Mn (91.80) > Zn (30.12) > Cr (15.00) > Pb (13.12) > Cu (3.53) > Ni (3.30) > As (0.51) > Cd (0.08) > Hg (0.04). Significant correlation among Fe, Mn, and heavy metals shows that solubilization by the method 3051A provides a reasonable estimate for predicting background concentrations for Cd, Cr, and Cu as well as Zn, Cr, Cu, and Ni. [ABSTRACT FROM AUTHOR]

The ecological water conveyance project (EWCP) in the lower reaches of the Tarim River provided a valuable opportunity to study hydro-ecological processes of desert riparian vegetation. Ecological effects of the EWCP were assessed at large spatial and temporal scales based on 13 years of monitoring data. This study analyzed the trends in hydrological processes and the ecological effects of the EWCP. The EWCP resulted in increased groundwater storage-expressed as a general rise in the groundwater table-and improved soil moisture conditions. The change of water conditions also directly affected vegetative cover and the phenology of herbs, trees, and shrubs. Vegetative cover of herbs was most closely correlated to groundwater depth at the last year-end ( R = 0.81), and trees and shrubs were most closely correlated to annual average groundwater depth ( R = 0.79 and 0.66, respectively). The Normalized Difference Vegetation Index (NDVI) responded to groundwater depth on a 1-year time lag. Although the EWCP improved the NDVI, the study area is still sparsely vegetated. The main limitation of the EWCP is that it can only preserve the survival of existing vegetation, but it does not effectively promote the reproduction and regeneration of natural vegetation. [ABSTRACT FROM AUTHOR]

Semiarid northwestern Mexico presents a growing water demand produced by agricultural and domestic requirements during the last two decades. The community of Guadalupe Valley and the city of Ensenada rely on groundwater pumping from the local aquifer as its sole source of water supply. This dependency has resulted in an imbalance between groundwater pumpage and natural recharge. A two-dimensional groundwater flow model was applied to the Guadalupe Valley Aquifer, which was calibrated and validated for the period 1984-2005. The model analysis verified that groundwater levels in the region are subject to steep declines due to decades of intensive groundwater exploitation for agricultural and domestic purposes. The calibrated model was used to assess the effects of different water management scenarios for the period 2007-2025. If the base case (status quo) scenario continues, groundwater levels are in a continuous drawdown trend. Some wells would run dry by August 2017, and water demand may not be met without incurring in an overdraft. The optimistic scenario implies the achievement of the mean groundwater recharge and discharge. Groundwater level depletion could be stopped and restored. The sustainable scenario implies the reduction of current extraction (up to about 50 %), when groundwater level depletion could be stopped. A reduction in current extraction mitigates water stress in the aquifer but cannot solely reverse declining water tables across the region. The combination of reduced current extraction and an implemented alternative solution (such as groundwater artificial recharge), provides the most effective measure to stabilize and reverse declining groundwater levels while meeting water demands in the region. [ABSTRACT FROM AUTHOR]

In this semi-arid area, many studies focused on the two-phase vegetation pattern were carried out to explore a changing vegetation trajectory on degraded land. However, this study conducted an analysis of a two-phase vegetation pattern and explored the successional vegetation trajectories in a positive succession without disturbance. In this work, 60 randomly distributed plots (1 × 1 m) were invested on four abandoned land areas (4-, 12-, 22-, and 50-year abandoned land) to determine attributes of vegetation, and soil physical and nutritional properties. It was found that vegetation distribution development went from homogeneous on 4-year abandoned land to heterogeneous on 50-year abandoned land, with a positive succession. Meanwhile, there was a significant difference in soil physical and nutritional properties for the inside and outside of vegetation patches. Vegetation patches can supply better soil physical and nutritional properties for vegetation than bare patches along the abandoned time. Vegetation diversity changes without a regular trend which may be due to the effect of environment and interspecies competition. This work picked up the slack for vegetation patterns succession research and provided a quantitative analysis approach. [ABSTRACT FROM AUTHOR]

Labile fractions of soil organic matter (SOM) respond rapidly to land management practices and can be used as a sensitive indicator of changes in SOM. However, there is little information about the effect of agroforestry practices on labile SOM fractions in semiarid regions of China. In order to test the effects of land use change from monocropping to agroforestry systems on labile SOM fractions, we investigated soil microbial biomass C (MBC) and N, particulate organic matter C (POMC) and N (POMN), as well as total organic C (TOC) and total N (TN) in the 0- to 15-cm and the 15- to 30-cm layers in 4-year-old poplar-based agroforestry systems and adjoining monocropping systems with two different soil textures (sandy loam and sandy clay loam) in a semiarid region of Northeast China. Our results showed that poplar-based agroforestry practices affected soil MBC, POMC, and POMN, albeit there was no significant difference in TOC and TN. Agroforestry practices increased MBC, POMC, and POMN in sandy clay loam soils. However, in sandy loam soils, agroforestry practices only increased MBC and even decreased POMC and POMN at the 0- to 15-cm layer. Our results suggest that labile SOM fractions respond sensitively to poplar-based agroforestry practices and can provide early information about the changes in SOM in semiarid regions of Northeast China and highlight that the effects of agroforestry practices on labile SOM fractions vary with soil texture. [ABSTRACT FROM AUTHOR]

Inland lakes are major surface water resource in arid regions of Central Asia. The area changes in these lakes have been proved to be the results of regional climate changes and recent human activities. This study aimed at investigating the area variations of the nine major lakes in Central Asia over the last 30 years. Firstly, multi-temporal Landsat imagery in 1975, 1990, 1999, and 2007 were used to delineate lake extents automatically based on Normalized Difference Water Index (NDWI) threshold segmentation, then lake area variations were detailed in three decades and the mechanism of these changes was analyzed with meteorological data and hydrological data. The results indicated that the total surface areas of these nine lakes had decreased from 91,402.06 km to 46,049.23 km during 1975-2007, accounting for 49.62% of their original area of 1975. Tail-end lakes in flat areas had shrunk dramatically as they were induced by both climate changes and human impacts, while alpine lakes remained relatively stable due to the small precipitation variations. With different water usage of river outlets, the variations of open lakes were more flexible than those of other two types. According to comprehensive analyses, different types of inland lakes presented different trends of area changes under the background of global warming effects in Central Asia, which showed that the increased human activities had broken the balance of water cycles in this region. [ABSTRACT FROM AUTHOR]

Airborne particle concentration (APC) measurements were carried out at the Sede Boker experimental station located in the northern Negev Desert, about 50 km south of Beer Sheva, during the years 1987–1997. The basic sampling period used in 1987–1993 was 12 h (day and night) and in 1994–1997 the sampling period was 24 h. For the entire study period, the average airborne particle concentration (APC) was 123.8 μg/m3, the highest value was 4204.2 μg/m3; and the lowest, near 5 μg/m3. For the 24 h average, about 90% of the cases were defined as normal situations (APC between 0–200 μg/m3) about, 8.5%, hazy periods (APC between 200–500 μg/m3), 1.4% dusty periods (APC between 500–1000 μg/m3) and about 0.7% were intense dusty periods (APC above 1000 μg/m3). Statistical analysis of the data showed significant seasonal and monthly fluctuations. The seasonal variation of the APC was further examined using different definitions of the seasons (astronomical, meteorological, and synoptic). [ABSTRACT FROM AUTHOR]

This study evaluates whether the size structure of seston (the sum of living and nonliving particles in the water column) reflects the effects of fish on wetland water quality. Using enclosures, we measured water quality and zooplankton community structure in the presence and absence of two fish species with distinct foraging strategies [benthivorous carp ( Cyprinus carpio) and planktivorous mosquitofish ( Gambusia holbrooki)]. Seston collected from the enclosures was counted and sized automatically with a Coulter counter, and the size structure in the range of 1–60 μm was modelled using the underlying Pareto distribution of particles. Only Cyprinus contributed to a loss of water quality (increased nutrient levels, algal and non-algal turbidity, hypoxia), while both fish species changed zooplankton community composition compared to fishless controls. However, these changes were not reflected in parameters [goodness of fit ( r 2) and parameter c (slopes)] of Pareto models. Multivariate statistics suggest that seston size structure responded more to environmental gradients related to water depth but the relationships were also weak. Our overall result contrasts with the regulation of size spectra constructed from living organisms. Although seston integrates many structural and functional features of the water column, the lack of strong relationships between Pareto model parameters and water quality suggests that a size-based approach to characterise seston structure has a limited potential for assessing biota-mediated effects in wetlands in a straightforward manner. [ABSTRACT FROM AUTHOR]

Thermal stress poses significant direct and indirect risks to human health. Under climate change, both mean temperature and the frequency and intensity of extreme thermal stress events are projected to increase. Located within an arid to semi-arid region, Iran is anticipated to experience particularly intense temperature and humidity changes under climate change, potentially heightening the public health challenges associated with thermal stress. To facilitate improved adaptation to these thermal threats, accurate high spatial resolution thermal heat stress risk maps are important. This study combines various climate indices to produce such a thermal stress risk map for the reference period 1980–2010, with RCP4.5 projections for the period 2020–2049. Although the results of the various indices are statistically significantly correlated, each index returned a remarkably different spatial distribution and risk classification. Therefore, a fuzzy approach was followed through a geographical information system (GIS) to combine the results of the five bioclimatic indices and prepare a final thermal stress risk map. Based on the RCP4.5 scenario, the results indicate a notable 24.5% reduction in the areas susceptible to thermal stress at the high-risk and very high–risk levels, compared with the reference period. The lowest projected risk is for the central parts of Iran, while the southern and northern coasts of Iran were the zones of the highest risk, for which adaptation responses are most necessary. [ABSTRACT FROM AUTHOR]

In light of ongoing changes in how humans interact with the environment, it is of great importance to quantitatively assess the impact of land use and cover change (LUCC) on ecosystems. Using a variety of methods, we analyzed land-use patterns and ecosystem service values (ESV) in 1990, 2000, and 2010; normalized difference vegetation index (NDVI) from 1982 to 2010 in the arid region of Northwest China; and quantitatively assessed the effects of LUCC on changes in NDVI and ESV. The results indicate the following: (1) From 1990 to 2010, the rate of increase in the amount of cropland and urban land was highest at 19.13% and 18.25%, respectively, followed by the rate for water cover (5.10%) and forest land (3.55%), while grassland experienced a reduction of 2.25%. (2) From 1990 to 2010, the total ESV increased by 1.82%. Changes in the amount of water cover and cropland were responsible for an increase in ESV of 1.42% and 1.10%, respectively, while the change in the amount of grassland was responsible for a decrease of 1.09%. Based on this, it seems likely that climate variability is a substantial cause of change in ESV. (3) From 1982 to 2010, NDVI showed an overall increase, first increasing significantly between 1982 and 2002 and then decreasing somewhat from 2002 to 2010. From 1990 to 2010, the contribution rate of LUCC to change in total NDVI was 26.74%, indicating that the contribution rate of climate variability to NDVI change was up to 73.26%. Therefore, over those 20 years, climate warming and humidification had an important impact on the development of ecosystems in the arid region of Northwest China. [ABSTRACT FROM AUTHOR]

Transpiration plays a key role in water and energy fluxes at various scales. While in recent remote sensing offers a fast and convenient method for tracing transpiration at multiple scales, the approach is mostly indirect and relies on energy balance. Although several hyperspectral indices have been reported to show potentials for tracing transpiration directly, both at leaf and canopy scales, they remain in pioneer stages and need extensive validations. In this study, we used the Soil, Canopy Observation, Photochemistry and Energy fluxes (SCOPE) model calibrated to arid ecosystems in Central Asia, to generate a simulated dataset for validation. Furthermore, new and robust indices have been developed by combining both simulated and in situ measured datasets. Results suggested that the SR(1525, 2150), ND(1425, 2145), and previously reported index of dSR(660,1040) have significant relationships with both simulated and in situ measured transpiration. Further analyses revealed that the ND(1425,2145) shows consistent performance, even with different methodologies of combining simulation and field-measured datasets. Statistically significant results were obtained in this study, even for a dominant drought-tolerant species in arid land, a place that typically has weak vegetation reflectance under strong background radiation. We foresee the approach being conducted in other regions where vegetation reflectance dominates. This may lead to robust hyperspectral indices being developed for directly tracing transpiration at various scales. [ABSTRACT FROM AUTHOR]

Semi-arid regions across the globe are fronting water crises, signaling a challenge to ensure future water security. Given the high inter-seasonal rainfall variability and unrestrained groundwater extraction, the precise quantification of groundwater flow components in an aquifer system is a priority. To address this challenge, we used high-resolution remote sensing (RS) data (Landsat and IRS) and GIS modeling (SEBAL, ArcCN) to spatially quantify major groundwater balance (GWB) components, viz., evapotranspiration (ET), rainfall recharge (R), surface runoff (Q), groundwater extraction (PG), irrigation return flow (IRF), and ultimately changes in groundwater storage (ΔS) in a small semi-arid crystalline representative watershed. Results show that a total of ~ 230 mm of groundwater is extracted during 2008-2009, creating a negative impact on the groundwater resource, which is further enhanced by limited recharge and high ET. A decrease of approximately 65 mm in groundwater storage is observed in a single hydrological year, and given a very low specific yield, this decrease will introduce large water level decline. The study establishes that declining groundwater level in the watershed is a direct result of over-extraction, and owing to this scenario, efficient irrigation and land use policies are suggested as potential approaches to minimize extraction specifically in the dry season. Our methodology provides a systematic assessment of vital GWB components at a high spatial resolution and an insight on various sustainable mitigation methods. This methodology is useful in the planning and management of groundwater resources, particularly in water-stressed areas. [ABSTRACT FROM AUTHOR]

Groundwater hazard assessments involve many activities dealing with the impacts of pollution on groundwater, such as human health studies and environment modelling. Nitrate contamination is considered a hazard to human health, environment and ecosystem. In groundwater management, the hazard should be assessed before any action can be taken, particularly for groundwater pollution and water quality. Thus, pollution due to the presence of nitrate poses considerable hazard to drinking water, and excessive nutrient loads deteriorate the ecosystem. The parametric IPNOA model is one of the well-known methods used for evaluating nitrate content. However, it cannot predict the effect of soil and land use/land cover (LULC) types on calculations relying on parametric well samples. Therefore, in this study, the parametric model was trained and integrated with the multivariate data-driven model with different levels of information to assess groundwater nitrate contamination in Saladin, Iraq. The IPNOA model was developed with 185 different well samples and contributing parameters. Then, the IPNOA model was integrated with the logistic regression (LR) model to predict the nitrate contamination levels. Geographic information system techniques were also used to assess the spatial prediction of nitrate contamination. High-resolution SPOT-5 satellite images with 5 m spatial resolution were processed by object-based image analysis and support vector machine algorithm to extract LULC. Mapping of potential areas of nitrate contamination was examined using receiver operating characteristic assessment. Results indicated that the optimised LR-IPNOA model was more accurate in determining and analysing the nitrate hazard concentration than the standalone IPNOA model. This method can be easily replicated in other areas that have similar climatic condition. Therefore, stakeholders in planning and environmental decision makers could benefit immensely from the proposed method of this research, which can be potentially used for a sustainable management of urban, industrialised and agricultural sectors. [ABSTRACT FROM AUTHOR]

Earlier studies by the authors on English soils under grassland strongly supported their hypothesis that soil/plant systems have naturally evolved to conserve nitrogen (N) by having a close match between the dynamics of mineral-N production in soils and the dynamics of plant N requirements. Thus, maximum mineral-N production in soils occurred in spring when plant N requirements were greatest and were very low in mid to late summer. Low temperature and a high C:N ratio of senescing material helped to conserve N in winter, but mobile N was associated with pollution inputs. We test the hypothesis that under the much more arid conditions of Pakistan, soil/plant systems naturally have evolved to conserve mineral-N, especially over the very dry and cooler months between October and February. When soils from a grassland site were incubated at ambient temperatures after removal of plant roots and exclusion of atmospheric N inputs, there was consistent evidence of immobilization of nitrate and immobilization and possibly volatilization of ammonia/ammonium. In the wetter months of July and August, the soil at 0-10 cm depth showed no evidence of significant ammonium-N production in July and only small ammonium production at 10-20 cm depth in August, but was associated with significant nitrate-N immobilization in August. Nitrate leaching only appeared likely towards the end of the rainy season in September. The results strongly suggest that, under grass, the retention of atmospheric N inputs over the long dry periods is regulating the pools of available N in the soils, rather than the N produced by mineralization of soil organic matter. [ABSTRACT FROM AUTHOR]