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Introduction: Climate change presents weighty challenges globally, with Nigeria particularly vulnerable to its multifaceted impacts. This review explores the effects of climate change-induced droughts and floods on food security in Nigeria, where agriculture is central to economic stability and livelihoods. Methods: The analysis integrates a comprehensive metadata evaluation, identifying trends, thematic gaps, and regional disparities in existing research. A systematic review of 2,500 publications, following PRISMA criteria, narrowed the focus to 450 studies, with 104 high-quality studies undergoing in-depth analysis. Results: Metadata analysis revealed an increase in research interest post-2010, a lack of longitudinal studies, and an underrepresentation of semi-arid northern regions in the literature. Findings indicate a growing threat to Nigeria's food security, as frequent flooding destroys infrastructure, erodes topsoil, and reduces agricultural productivity, leading to lower food output and increased costs. At the same time, droughts, particularly in the semi-arid north, drastically reduce crop yields and worsen food insecurity by depleting vital water resources. These challenges disproportionately affect smallholder farmers and pastoral communities, waning poverty and hunger. Discussion: The review highlights the complexity of Nigeria's food insecurity, shaped by factors such as geography, socioeconomic status, and adaptive capacity. Despite advancements in adaptation strategies, issues like fragmented policies and inadequate infrastructure continue to hinder effective responses. However, the review identifies key opportunities to enhance food security and resilience, including greater stakeholder engagement, increased investment in climate adaptation, and the use of digital technologies. By addressing these challenges and leveraging the opportunities, Nigeria can build a more resilient and sustainable food system capable of withstanding the increasing threats posed by climate change. [ABSTRACT FROM AUTHOR]

IntroductionClimate change presents weighty challenges globally, with Nigeria particularly vulnerable to its multifaceted impacts. This review explores the effects of climate change-induced droughts and floods on food security in Nigeria, where agriculture is central to economic stability and livelihoods.MethodsThe analysis integrates a comprehensive metadata evaluation, identifying trends, thematic gaps, and regional disparities in existing research. A systematic review of 2,500 publications, following PRISMA criteria, narrowed the focus to 450 studies, with 104 high-quality studies undergoing in-depth analysis.ResultsMetadata analysis revealed an increase in research interest post-2010, a lack of longitudinal studies, and an underrepresentation of semi-arid northern regions in the literature. Findings indicate a growing threat to Nigeria’s food security, as frequent flooding destroys infrastructure, erodes topsoil, and reduces agricultural productivity, leading to lower food output and increased costs. At the same time, droughts, particularly in the semi-arid north, drastically reduce crop yields and worsen food insecurity by depleting vital water resources. These challenges disproportionately affect smallholder farmers and pastoral communities, waning poverty and hunger.DiscussionThe review highlights the complexity of Nigeria’s food insecurity, shaped by factors such as geography, socioeconomic status, and adaptive capacity. Despite advancements in adaptation strategies, issues like fragmented policies and inadequate infrastructure continue to hinder effective responses. However, the review identifies key opportunities to enhance food security and resilience, including greater stakeholder engagement, increased investment in climate adaptation, and the use of digital technologies. By addressing these challenges and leveraging the opportunities, Nigeria can build a more resilient and sustainable food system capable of withstanding the increasing threats posed by climate change.

The Three Gorges Reservoir (TGR) is one of the world's largest hydropower projects and plays an important role in water resources management in the Yangtze River. For the sake of disaster prevention and catchment management, it is crucial to understand the regulation capacity of the TGR on extreme hydrological events and its impact on flow regime in a changing climate. This study obtains historical inflows of the TGR from 1961 to 2019 and uses a distributed hydrological model to simulate the future inflows from 2021 to 2070. These data are adopted to drive a machine learning‐based TGR operation model to obtain the simulated outflow with TGR operation, which are then compared with the natural flow without TGR operation to assess the impact of TGR. The results indicate that the average flood peaks and total flooding days in the historical period could have been reduced by 29.2% and 53.4% with the operation of TGR. The relative declines in drought indicators including duration and intensity were generally less than 10%. Faced with more severe extreme hydrological events in the future, the TGR is still expected to alleviate floods and droughts, but cannot bring them down to historical levels. The impact of TGR operation on flow regime will also evolve in a changing climate, potentially altering the habitats of river ecosystems. This study proposes feasible methods for simulating the operation of large reservoirs and quantifying the impact on flow regime, and provides insights for integrated watershed management in the upper Yangtze River basin. Plain Language Summary: The Three Gorges Reservoir (TGR) is located in the upper Yangtze River basin and is one of the world's largest hydropower projects. This study combines hydrological modeling and machine learning methods to quantify the effects of TGR operation on flow regime in the historical and future periods. The results indicate that the operation of TGR could play an important role in mitigating historical droughts and floods. Specifically, the flood peak in 1998 could have been reduced by 24.7% if the TGR was in operation. In the future, the extreme hydrological events will become more severe. While the TGR will continue to play a significant role, it cannot fully control floods and droughts to the same extent as it did in the historical period. In a changing climate, the Yangtze River basin will still face higher flood and drought risks with the operation of TGR. Under future climate scenarios, the operation of TGR will also alter the flow regime metrics and have new implications on the river ecosystem environment. Key Points: An ensemble learning model based on two neural networks is constructed to simulate Three Gorges Reservoir (TGR) operationsTGR can mitigate floods and droughts, but this capability might be weakened by more severe future extreme eventsTGR can offset most flow regime changes caused by climate change, but adaptive operation strategies are still needed [ABSTRACT FROM AUTHOR]

Floods are among the most devastating and financially burdensome natural disasters in Europe. The combined impact of climate change and land use change is expected to exacerbate and intensify the destructive consequences of river floods. In this study, we analysed the effects of wetland restoration on peak and base flows and on water quality in the Kylldal catchment of the Kyll River in the German Middle Mountains using the Soil and Water Assessment Tool+ (SWAT+). Monthly median daily discharge increases varied between 3% and 33% in the studied (micro)catchments. The higher median flow rates show that discharge peaks were attenuated and distributed over a longer period, making both extreme peak flows and low flows less common. Peak flows tended to decrease, with the largest effects between late fall and early spring when peak flow values decreased by up to 18%. The annual maximum peak flows in each of the three micro-catchments decreased by 12–24% on average. The occurrence of daily average flow rates larger than 1 m3 s−1 was up to 45% lower after wetland restoration. Low flows increased by up to 21% and 13% in the summer and fall, respectively, which suggests that drought risk also decreases after wetland restoration. Average nitrogen exports decreased by 38–50% in the project areas and by 20% at the catchment level. Average phosphorus exports decreased by 52–67% in the project areas and by 25% at the catchment level. The study highlights the potential of wetland restoration for improving hydrological services, mitigating flood risks, and enhancing water quality. Restoring and maintaining freshwater ecosystems and their natural sponge functions is crucial for effectively managing water resources and addressing the challenges posed by climate change and land use changes. [ABSTRACT FROM AUTHOR]

Urban development and climate change have strengthened the possibility of floods and droughts in cities. In this study, we evaluated the influences of these disasters and related social damage in nine major basins during the past 50 years. Unusually, the following conclusions were drawn from the analysis of relevant indicators before and after urbanization: (1) agricultural loss area (flood), grain loss, and direct economic loss showed an upward trend, while other indicators showed the opposite. (2) Floods most often occur in the Yangtze River Basin (58, 26.2%), followed by the Liaohe River Basin (49, 22.2%), which is closely related to the topography and economic progress of the area. (3) The modified Mann–Kendall (MK) analysis results are consistent with the indicators trend. Finally, the regularity of the climate change and urbanization process is revealed by the migration of the standard deviation ellipse and the mean center of the four indicators. China needs to integrate urban water/drought policy development with sustainable urbanization policy development to cope with the changing natural and social environment and to minimize urban ecological risks. [ABSTRACT FROM AUTHOR]

In this mini-review, we present evidence from the vast literature that one essential part of the coupled atmosphere–ocean system that makes life on Earth possible, the water cycle, is exhibiting changes along with many attributes of the global climate. Our starting point is the 6th Assessment Report of the IPCC, which appeared in 2021, where the almost monograph-size Chapter 8, with over 1800 references, is devoted entirely to the water cycle. In addition to listing the main observations on the Earth globally, we focus on Europe, particularly on the Carpathian (Pannonian) Basin. We collect plausible explanations of the possible causes behind an observably accelerating and intensifying water cycle. Some authors still suggest that changes in the natural boundary conditions, such as solar irradiance or Earth's orbital parameters, explain the observations. In contrast, most authors attribute such changes to the increasing greenhouse gas concentrations since the industrial revolution. The hypothesis being tested, and which has already yielded convincing affirmative answers, is that the hydrological cycle intensifies due to anthropogenic impacts. The Carpathian Basin, a part of the Danube watershed, including the sub-basin of the Tisza River, is no exception to these changes. The region is experiencing multiple drivers contributing to alterations in the water cycle, including increasing temperatures, shifting precipitation regimes, and various human impacts. [ABSTRACT FROM AUTHOR]

Study region: Nenjiang River Basin (NRB), Northeast China. Study focus: Water safety management and sustainable development planning increasingly seek to incorporate the impact of reservoirs on downstream floods and droughts; while the effectiveness of reservoir operation in regulating flood and drought risks under climate change has not been assessed extensively. We focus on discerning whether and to what extent reservoirs can mitigate the risk of hydrologic extremes from the perspective of historical and future climate change. New hydrological insight for the region: We found that coupling reservoir operations into basin hydrological simulation can efficiently improve model capacity to capture both flood and hydrological drought characteristics. The Nierji Reservoir contributed largely to reducing historical flood and drought risks in the NRB. However, the risk of floods and hydrological droughts will increase under future climate change, and reservoir operations cannot completely eliminate the increasing risks of future floods and hydrological droughts. The annual probability of flooding under different future scenarios will exceed 48%, much higher than the 22.2% for the historical period. The frequency of droughts is anticipated to increase by 139.20% under the Shared Socioeconomic Pathways (SSP) 370 scenario. To mitigate the increase of flood and drought risks caused by future climate change, it is necessary to further optimize reservoir scheduling principles, thereby improving the basin's resilience to hydrological extremes.

Two late Holocene cold events were described for the Southern Russian Far East: 2800–2600 year BP and the Little Ice Age (LIA) (~1300–1850 CE). The synthesis is based on multi-proxy records on profile "the mainland (Primorye)-islands (Sakhalin-Kurils)". Main archives are sediments of small lakes and peat bogs that recorded the high-resolution environmental changes. The temporal resolution of reconstructions here is up to 26–40 years. During the cold event of 2800–2600 year BP, the humidity decreased sharply, there were long-term dry seasons without strong floods, and buried soil formed on floodplains. The LIA was wet in the mainland and the Kurils, with frequent strong floods, but was drier in Sakhalin. The cooling was characterized by sharp temperature fluctuations where high moisture conditions alternated with short-term drier periods. The shift in geographical position and intensity of the main centers of atmospheric action caused a paleoclimatic interpretation of these events (Aleutian Low, Siberian and North Pacific Highs, the summer Okhotsk anticyclone and the Far East depression). Changes in the North Pacific oscillations played an important role in the alternation of cold-dry and cold-wet periods. Anomalies in the intensity of El Niño and the monsoon system led to changes in tropical and extratropical cyclone trajectories and cyclogenesis in general. [ABSTRACT FROM AUTHOR]

This study outlines a framework for examining potential impacts of future climate change in Poyang Lake water levels using linked models. The catchment hydrological model (WATLAC) was used to simulate river runoffs from a baseline period (1986–2005) and near-future (2020–2035) climate scenarios based on eight global climate models (GCMs). Outputs from the hydrological model combined with the Yangtze River's effects were fed into a lake water-level model, developing in the back-propagation neural network. Model projections indicate that spring–summer water levels of Poyang Lake are expected to increase by 5–25%, and autumn–winter water levels are likely to be lower and decrease by 5–30%, relative to the baseline period. This amounts to higher lake water levels by as much as 2 m in flood seasons and lower water levels in dry seasons in the range of 0.1–1.3 m, indicating that the lake may be wet-get-wetter and dry-get-drier. The probability of occurrence for both the extreme high and low water levels may exhibit obviously increasing trends by up to 5% more than at present, indicating an increased risk in the severity of lake floods and droughts. Projected changes also include possible shifts in the timing and magnitude of the lake water levels.

The objective of this study is to present a comprehensive water risk management plan for the Napostá Grande watershed, in the southwest of Buenos Aires province (Argentina). The definition of programs is used, articulated in projects and activities to be applied in the short, medium and long term. Taking into account the review of specific bibliography, scientifictechnical reports, land use planning plans and interviews carried out with social actors from the scientific and political sphere, it is evident that in the study area the lack of articulation between the interventions carried out in the upper, middle and lower basin depending on the type of settlement, socio-economic activities developed and the perception and social representations of water risk built. The results express that although the proposed plan includes threats and weaknesses, it also includes opportunities and strengths that must be considered, taking into account a prospective, multiscale and trans-scale vision of spatial processes. The plan presented thus constitutes a valuable tool that can be used in various geographical situations as a model for the establishment of intervention strategies that promote the reduction of risk scenarios and guide territorial planning and decision-making. [ABSTRACT FROM AUTHOR]

Water resources management is a critical issue in Africa where many regions are subjected to sequential droughts and floods. The objective of our work was to assess spatiotemporal variability in water storage and related controls (climate, human intervention) in major African aquifers and consider approaches toward more sustainable development. Different approaches were used to track water storage, including GRACE/GRACE Follow On satellites for Total Water Storage (TWS); satellite altimetry for reservoir storage, MODIS satellites for vegetation indices, and limited ground-based monitoring. Results show that declining trends in TWS (60–73 km ^3 over the 18 yr GRACE record) were restricted to aquifers in northern Africa, controlled primarily by irrigation water use in the Nubian and NW Saharan aquifers. Rising TWS trends were found in aquifers in western Africa (23–49 km ^3 ), attributed to increased recharge from land use change and cropland expansion. Interannual variability dominated TWS variability in eastern and southern Africa, controlled primarily by climate extremes. Climate teleconnections, particularly El Nino Southern Oscillation and Indian Ocean Dipole, strongly controlled droughts and floods in eastern and southern Africa. Huge aquifer storage in northern Africa suggests that the recent decadal storage declines should not impact the regional aquifers but may affect local conditions. Increasing groundwater levels in western Africa will need to be managed because of locally rising groundwater flooding. More climate resilient water management can be accomplished in eastern and southern Africa by storing water from wet to dry climate cycles. Accessing the natural water storage provided by aquifers in Africa is the obvious way to manage the variability between droughts and floods.

Extreme weather and climate variability have become a subject of big concern worldwide. In response, efforts have been made to evaluate the trends in climatic parameters in two geographical regions of India – Northeast (NER) and West coast region (WCR) for the period 1901-2009. This paper studies trends in cyclones and depressions, floods and droughts, thunderstorms, hailstorms, the number of fog and poor visibility days in the research areas. A detailed analysis indicates a mixed trend for cyclones and depressions, flood and drought events. Moderate and severe cold waves also show a significant decreasing trend. The same behaviour is observed in the frequency of heat waves too. There is a significant increase in thunderstorm and hailstorm frequency. During the winter season, fog and poor visibility days show a positive correlation in Imphal, Kailashahar and Agartala. It can be concluded that in the midst of global warming and climate change, the climate response is mixed for both regions.

Global perspectives on the complexities of environmental change impacts associated with past and present human activity are needed for the food and water security challenges of the twenty-first century. This is especially true for rivers, for which the onset and persistence of a range in human activities, altering their function and form, have been temporally and spatially variable. Ancient civilisations, states and empires extended geographically to cover sub-continental areas where their river modifying activities became linked to regional Earth system stresses arising from climate and land use change. We present a new interpretative framework for characterising and classifying human impact on river systems, emphasising that this has taken place over decadal to millennial time periods on a sub-continental scale. This 16-element classification and documentation of different human transformations, including land management, urbanisation, industry and engineering activities, is used to explore anthropogenic channel and floodplain disruptions that have followed each other in different sequences in different places. It is significant that these inadvertent and deliberate human interventions have also taken place in parallel with contrasting climatic fluctuations that have been sub-continental in scale and varied in time. We assess the influence of the dominant modes of regional climate variability (monsoons, El Niño Southern Oscillation, Indian Ocean Dipole, North Atlantic Oscillation, Pacific Decadal Oscillation and Siberian High) on the speed and pattern of river system adjustment to anthropogenic perturbations. Some river civilisations have proved resilient to change given their adaptive management, while others have been overwhelmed by climate-related changes in river morphodynamics. We conclude that integrated socioeconomic, climatic and hydromorphological histories provide usefully instructive antecedents for sensibly managing, as they evolve, the even more serious coupled environmental stresses likely in the future. [ABSTRACT FROM AUTHOR]

Although many large-N quantitative studies have evidenced the adverse effects of climatic extremes on social stability in China during the historical period, most of them rely on temperature and precipitation as major explanatory variables, while the influence of floods and droughts on social crises is rarely measured. Furthermore, a comparison of the climate-society nexus among different geographic regions and at different temporal scales is missing in those studies. To address this knowledge gap, this study examines quantitatively the influence of floods and droughts on internal wars in three agro-ecological (rice, wheat, and pastoral) regions in China in AD1470-1911. Poisson regression and wavelet transform coherence analyses are applied to allow for the non-linear and non-stationary nature of the climate-war nexus. Results show that floods and droughts are significant in driving internal wars in historical China, but are characterized by strong regional variation. In the rice region, floods trigger internal wars at the inter-annual and multi-decadal time scales. In the wheat region, both floods and droughts cause internal wars at the inter-annual and multi-decadal time scales. In the pastoral region, internal wars are associated with floods only at the multi-decadal time scale. In addition, the multi-decadal coherence between hydro-climatic extremes and internal wars in all three of the agro-ecological regions is only significant in periods in which population density is increasing or the upper limit of regional carrying capacity is being reached. The above results imply that the climate-war nexus is mediated by regional geographic factors such as physical environmental setting and population pressure. Hence, we encourage researchers who study the historical human-climate relationship to boil down data according to geographic regions in the course of statistical analysis and to examine each region individually in follow-up studies. [ABSTRACT FROM AUTHOR]

Changes in climate because of global warming during the 20th and 21st centuries have a direct impact on the hydrological cycle as driven by precipitation. However, studying precipitation over the Western Maritime Continent (WMC) is a great challenge, as the WMC has a complex topography and weather system. Understanding changes in precipitation patterns and their groupings is an important aspect of planning mitigation measures to minimize flood and drought risk as well as of understanding the redistribution of precipitation arising from climate change. This paper employs Ward's hierarchical clustering on regional climate model (RCM)-simulated monthly precipitation gridded data over 42 approximately evenly distributed grid stations from the years 2030 to 2060. The aim was to investigate spatial and temporal groupings over the four major landmasses in the WMC and to compare these with historical precipitation groupings. The results showed that the four large-scale islands of Java, Sumatra, Peninsular Malaysia and Borneo would experience a significant spatial redistribution of precipitation over the years 2030 to 2060, as compared to historical patterns from 1980 to 2005. The spatial groups were also compared for two future forcing scenarios, representative concentration pathways (RCPs) 4.5 and 8.5, and different groupings over the Borneo region were observed. [ABSTRACT FROM AUTHOR]

In China, cities are normally built along rivers. The capital of China has changed several times since the establishment of the Xia dynasty, the first dynasty of China. However, most of the capital cities were located along the middle and lower reaches of the Yellow River. The Yellow River system, composed of the Yellow River and its tributaries, has exerted huge effects on the rise and fall of the ancient capitals. Xi'an, Luoyang and Kaifeng are known as the most important, the most famous and the longest-serving capitals of ancient China along the middle and lower reaches of the Yellow River. Focusing on the three historical capitals, this study investigated how changes in the Yellow River system, floods and droughts, and the development of water transport had affected the courses of development of China's ancient capitals. [ABSTRACT FROM AUTHOR]

Uncertainties exist regarding the magnitude of in situ dissolved organic matter (DOM) processing in lotic systems. In addition, little is known about the effects of extreme hydrological events on in-stream DOM retention or release during downriver transport. This study quantified the net in-stream retention/release efficiencies ( η ) of dissolved organic carbon (DOC) and its humic and protein-like fluorescent fractions along a Mediterranean river during drought, baseflow and flood conditions. High performance size exclusion chromatography was used to describe the apparent size distributions of the humic and protein-like DOM moieties. A snapshot mass balance allowed estimating the η values of DOC and humic and protein-like fractions. Significant DOM net retention ( η < 0) was detected during the drought condition and the protein-like fraction was more retained than the humic-like fraction and bulk DOC. In addition, small substances were more efficiently retained than larger substances. DOC retention decreased under baseflow conditions, but it remained significant. The humic and protein-like net efficiencies exhibited high variability, but the net retention were not significant. From a longitudinal perspective, the entire fluvial corridor contributed net retention of DOC and humic and protein-like moieties net retention during drought condition. In contrast, net retention/release efficiencies exhibited spatial variability during baseflow condition. The flood preferentially mobilized large size DOM molecules and the fluvial corridor behaved as a homogeneous passive DOM ( η = 0 ) conduit. This research highlights the relevance of hydrological extreme events on the magnitude of DOM retention/release mass balance and emphasizes the need to perform measurements during these conditions to quantify the impact of fluvial corridors on DOM fate and transport. [ABSTRACT FROM AUTHOR]

Pakistan has become a poster child for extreme weather events such as floods and droughts in recent years. The frequency and severity of these events are expected to increase in the future due to predicted climatic changes. This scenario suggests the likelihood of increased crop damage in flood- or drought-prone areas, and hence the need for risk-reducing mechanisms. This paper attempts to determine whether crop insurance is an acceptable tool against flood and drought events in rural Pakistan. It also analyses the factors influencing a farmer's willingness to pay insurance premiums. In a rural farm-household survey, farmers were asked about their willingness to pay for a hypothetical crop insurance programme employing a “double-bounded dichotomous contingent valuation method”. The results revealed that around 30% of the respondents accepted the idea of crop insurance as a tool to reduce and mitigate the financial risks associated with floods and droughts. Our findings suggest that the frequency and severity of the previous weather-related extremes, socio-economic settings, farm typology and the farming communities’ ability to pay need to be taken into consideration when introducing crop insurance programmes against flood or drought in Pakistan. Furthermore, disseminating awareness among farming communities about the future climatic changes and the associated risks of the occurrence of extreme weather events is imperative. The government's willingness to share/subsidize insurance premiums may increase the demand for crop insurance among smallholders in Pakistan and protect them from the negative repercussions of these extreme weather events in order to sustain their livelihoods. [ABSTRACT FROM PUBLISHER]

New approaches that are cost effective and sustainable are needed globally to better manage flood and drought impacts. Recharging monsoon floodwaters in upstream areas to boost small-scale groundwater irrigation and to protect flood-affected urbanized areas downstream is proposed as one such approach and has been termed ‘Underground Taming of Floods for Irrigation’ (UTFI). Prospective locations for implementing UTFI are identified using a GIS-based method specifically developed here. There are three main steps to the method: (1) pre-feasibility analysis, (2) spatial data processing, and (3) index determination to rank prospects for establishing UTFI interventions. The methodology was applied to watersheds within the Ganges River Basin in South Asia. Data on the drainage density, flood frequency, flood mortality and distribution, extreme rainfall events, landuse, population density, geology, slope, soil, groundwater level, aquifer transmissivity and economic loss due to floods were used. The ranking and overlay index method adopted in arriving at the final suitability map showed that within the 43 % of the Ganges that is routinely subjected to floods, 68 % of this area had either ‘very high’ or ‘high’ suitability. Most important parameters identified from the sensitivity analysis were flood mortality and distribution, flood frequency and extent, drainage density and groundwater level. Suitability index values were generated for watersheds of different sizes which showed that smaller watersheds (100 km2 or less) provide better results but that up to 1000 km2 was considered acceptable. These results can be useful for prioritizing areas to apply integrated flood and drought management measures. The approach developed here may be directly transferable to other river basins. [ABSTRACT FROM AUTHOR]

Extreme weather and climate variability have become a subject of big concern worldwide. In response, efforts have been made to evaluate the trends in climatic parameters in two geographical regions of India - Northeast (NER) and West coast region (WCR) for the period 1901-2009. This paper studies trends in cyclones and depressions, floods and droughts, thunderstorms, hailstorms, the number of fog and poor visibility days in the research areas. A detailed analysis indicates a mixed trend for cyclones and depressions, flood and drought events. Moderate and severe cold waves also show a significant decreasing trend. The same behaviour is observed in the frequency of heat waves too. There is a significant increase in thunderstorm and hailstorm frequency. During the winter season, fog and poor visibility days show a positive correlation in Imphal, Kailashahar and Agartala. It can be concluded that in the midst of global warming and climate change, the climate response is mixed for both regions. [ABSTRACT FROM AUTHOR]

This study analyses the changing characteristics in the level of Poyang Lake during the period 1960–2010. Results show that the changing stage of annual lake level variations is evident, and average onset time of the lake dry season has advanced since the 1990s. Investigation indicates that the Yangtze River discharge has a greater impact on annual lake level variations than the lake’s catchment inflow. Climate change in the Yangtze River basin since the 1990s is possibly the precondition for the advance of the lake dry season, which is further aggravated by the effects of the Three Gorges Dam in the 2000s. [ABSTRACT FROM AUTHOR]

The Water Framework Directive sets out a series of deadlines for implementation that are proving hard to meet as a result of the economic recession. In addition to which, we also have to face the serious challenges affecting the Spanish water situation: floods, droughts, water shortages in Eastern Spain, without ignoring the need to conserve the wealth of waterworks in the country. This article discusses a series of points and measures concerning the stakeholders involved and covering different areas of action related to water These measures are all geared to stimulating this sector by productive investment which would help create employment. [ABSTRACT FROM AUTHOR]

The present study has been taken up to quantify the possible impact of the climate change on the water resources of Indian river systems within the constraints of the uncertainty of climate change predictions. The study uses the PRECIS daily weather data to determine the spatio-temporal water availability in the river systems. A distributed hydrological model, namely SWAT has been used to simulate all the river basins of the country. The analysis has been performed to evaluate the severity of droughts and floods and thus identify the vulnerable hotspots that may require attention in view of the climate change in various parts of the country. The analysis is also performed on the blue and green water so as to identify the climate change impacts on these sub-components of water that are responsible for environmental functions and biomass production. These results have been made available at http://gisserver.civil.iitd.ac.in/natcom for use by a large cross-section of users. [ABSTRACT FROM AUTHOR]

1. We used information theoretic statistics [Akaike’s Information Criterion (AIC)] and regression analysis in a multiple hypothesis testing approach to assess the processes capable of explaining long-term demographic variation in a lightly exploited brook trout population in Ball Creek, NC. We sampled a 100-m-long second-order site during both spring and autumn 1991–2004, using three-pass electrofishing. 2. Principle component analysis indicated that the site had lower average velocity, greater amounts of depositional substrata and lower amount of erosional substrata during the 1999–2002 drought than in non-drought years. In addition, drought years had lower flows, and lower variation in flows, than non-drought years. 3. Both young-of-the-year (YOY) and adult densities varied by an order of magnitude during the study. AIC analysis conducted on regressions of per capita rate of increase versus various population and habitat parameters for the population, adults and YOY, for both spring and autumn data sets, indicated that simple density dependence almost always was the only interpretable model with Akaike weights ( wi) ranging from 0.262 to 0.836. 4. Growth analyses yielded more variable results, with simple density dependence being the only interpretable model for both adult spring data ( wi = 0.999) and YOY autumn data ( wi = 0.905), and positive density dependence ( wi = 0.636) and simple density independence ( wi = 0.241) representing interpretable models for spring YOY data. 5. We detected a significant stock–recruitment relationship between both spring and autumn densities of adults in year t and autumn YOY density in year t + 1. Finally, spring YOY density was positively correlated with both autumn YOY density and spring mean YOY standard length (SL), suggesting that processes affecting recruitment show residual effects at least in the first year of life. This population appears to be regulated primarily by density-dependent processes, although high flows also negatively affected mean SLs of YOY. [ABSTRACT FROM AUTHOR]

Summary: Repeated severe floods and damages in the Poyang Lake basin in China during the 1990s have raised the concern of how the floods have been affected by regional climate variations and by human induced changes in landscape (e.g., draining wetlands around the lake) and land-use in the basin. To address this concern and related issues it is important to know how the climate, land-use and land-cover changes in the region affect the annual and seasonal variations of basin hydrology and streamflow. This knowledge is essential for long-term planning for land-use to protect water resources and to effectively manage floods in the Poyang Lake basin as well as the lower reaches of the Yangtze River. It also has important ecological and socioeconomic implications for the region. This study used the SWAT model to examine the climate and land-use and land-cover effects on hydrology and streamflow in the Xinjiang River basin of the Poyang Lake. A major finding of this study is that the climate effect is dominant in annual streamflow. While land-cover change may have a moderate impact on annual streamflow it strongly influences seasonal streamflow and alters the annual hydrograph of the basin. Because of the vegetation and associated seasonal variations of its impact on evapotranspiration, increase of forest cover after returning agricultural lands to forest reduces wet season streamflow and raises it in dry season, thus reducing flood potentials in the wet season and drought severity in the dry season. On the other hand, losing forests increases flood potential and also enhances drought impacts. Results of this study improve our understanding of hydrological consequences of land-use and climate changes, and provide needed knowledge for effectively developing and managing land-use for sustainability and productivity in the Poyang Lake basin. [Copyright &y& Elsevier]

Floods and droughts are natural phenomena of difficult prevision. Awareness, mitigation and water resource management, depend upon timely information on the beginning of a dry or wet period and on their extension in time and space. This study predicts SPI steady state class probabilities in the Douro region, Portugal, through an empirical and Markov chain approach, expected residence time in each class of severity; expected first passage time, recurrence time and class prediction in a short-term basis. It was verified that all these variables are useful for water resources management. [ABSTRACT FROM AUTHOR]

Although Meiyu rainfall has its in-phase spatial variability over the Changjiang-Huaihe River Valley (CHRV) in most years, it is distributed in some years like a seesaw to the north and south of the Changjiang River, when the precipitation tends to be nearly normal throughout the valley, which would inevitably increase difficulties of making short-term prediction of the rainfall. For this reason, EOF analysis is made on 15 related stations' precipitation from June to July during 1951-2004, revealing that the EOF2 mode shows largely a north-south seesaw-like pattern, and thereby classifying Meiyu patterns into two types: ‘northern drought and southern flood (NDSF)’ and ‘northern flood and southern drought (NFSD)’. Afterwards, the authors investigated ocean-atmospheric characteristics when these two anomalous types occurred using the NCEP reanalysis (version 1) and the extended reconstructed SSTs (version 2). The results show that in the NDSF years, the low-level frontal area and moisture convergence center lie more southward, accompanied by weaker subtropical summer monsoon over East Asia, with the western Pacific subtropical high and 200 hPa South Asia High being more southward. Both the Northern and Southern Hemisphere Annular Modes are stronger than normal in preceding February; SST is higher off China during boreal winter and spring and the opposite happens in the NFSD years. Also, this seesaw-form Meiyu rainfall distribution might be affected to some degree by the previous ENSO event. [ABSTRACT FROM AUTHOR]

We used strong inference with Akaike's Information Criterion (AIC) to assess the processes capable of explaining long-term (1984-1995) variation in the per capita rate of change of mottled sculpin (Cottus bairdi) populations in the Coweeta Creek drainage (USA). We sampled two fourth- and one fifth-order sites (BCA [uppermost], BCB, and CC [lowermost]) along a downstream gradient, and the study encompassed extensive flow variation. Physical habitat availability varied significantly both within and among the sites. Sculpin densities in all sites were highly stable (coefficients of variation = 0.23-0.41) and sampling variability was low (coefficients of variation = 0.11-0.15). Population stability was positively associated with habitat stability, and the only significant correlations of population parameters among sites involved juveniles. Sculpin densities were significantly higher in BCB than in CC. The data suggest that, despite their proximity, the dynamics of populations within the sites are being determined by small-scale (i.e., 30-50 m) rather than broad-scale spatial processes. Both AIC and Dennis and Taper analyses indicated that simple density dependence had the greatest ability to explain variation in r for all life-history classes in all sites (AIC, seven of nine cases; Dennis and Taper, nine of nine cases). Multiprocess models had little explanatory power. When adults were removed from two sites, juvenile sculpin shifted into microhabitats formerly occupied by adults. No shifts occurred in control sites. Consequently, it is likely that the patterns of density dependence observed in all three sites were a consequence of intraspecific competition for space. Our findings argue for a multitiered approach to the study of population variation, one that encompasses long-term monitoring, spatial variation, and experimental testing of potential mechanisms. [ABSTRACT FROM AUTHOR]

The Weihe River Basin (WRB) in a monsoon transition zone of East Asia interacts with multiple weather systems and is susceptible to floods and droughts. We developed a framework based on the Empirical Orthogonal Function analysis, Complete Ensemble Empirical Mode Decomposition with Adaptive Noise analysis, and moving-average based Spearman rank correlation to identify the spatial patterns of the dry/wet conditions from 1470 to 2016, decompose the dry/wet index into the leading components with a period between 2 and 3 years and 100+ years, and discover their driving forces on multiple time scales. Results show that WRB can be divided into four distinguishable hydroclimatic subregions located in the southeast, west, central, and north. The East Asian summer monsoon and South Asian summer monsoon impact this region mainly on the inter-annual and inter-decadal scales, while the impacts of ENSO, PDO, AO, and NAO are dominant on the multi-decadal and centennial scales. [Display omitted] • Developed a new framework to attribute dry/wet spatiotemporal variability on multiple time scales. • Revealed four unique hydroclimatic subregions for the Weihe River Basin. • Identified the effects of monsoons, plateau circulation, westerly, and solar activities on Weihe. • Dry/wet conditions of the subregions show opposite responses to solar activity. [ABSTRACT FROM AUTHOR]