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Climate variability and change greatly affect agricultural and water resource management over West Africa. This paper presents the current characteristics and projected change in regional crop water demand (CWD), irrigation requirement (IR), and water availability (WA) over West Africa. Observed and simulated daily rainfall, minimum temperature, maximum temperature, and evapotranspiration are used to derive the above agro-meteorological and hydrological variables. For future periods, high-resolution climate data from three regional climate models under two different scenarios, i.e., representative concentration pathway (RCP) 4.5 and 8.5, are considered. Evaluation of the characteristics of present-day CWD, IR, and WA indicated that the ensemble mean of the model-derived outputs reproduced the prevailing spatial patterns of CWD and IR. Moreover, the wetter part of the domain, especially along the southern coast, was correctly delineated from the drier northern regions, despite having biases. The ensemble model also simulated the annual cycle of water supply and the bimodal pattern of the water demand curves correctly. In terms of future projections, the outcomes from the study suggest an average increase in the CWD by up to 0.808 mm/day and IR by 1.244 mm/day towards the end of the twenty-first century, compared to the baseline period. The hot-spot areas, where there is higher projected increment in CWD and IR, are over Senegal, Southern Mali, and Western Burkina Faso. In most cases, WA is projected to decrease towards the end of the twenty-first century by −0.418 mm/day. The largest decline in WA is found to be over Guinea and most of the eastern parts of West Africa. Despite the current under-utilization of the existing groundwater resources, the threat of global warming in reducing future WA and increasing CWD suggested caution on the scale of irrigation schemes and management strategies. The outcomes from the study could be a crucial input for the agricultural and water managers for introducing effective measures to ensure sustainability of irrigated farm lands. [ABSTRACT FROM AUTHOR]

Background: Climate change has altered global hydrological cycles mainly due to changes in temperature and precipitation, which may exacerbate the global and regional water shortage issues, especially in the countries along the Belt and Road (B&R). Methods: In this paper, we assessed water supply, demand, and stress under three climate change scenarios in the major countries along the Belt and Road. We ensembled ten Global Climate Model (GCM) runoff data and downscaled it to a finer resolution of 0.1 × 0.1 by the random forest model. Results: Our results showed that the GCM runoff was highly correlated with the FAO renewable water resources and thus could be used to estimate water supply. Climate change would increase water supply by 4.85%, 5.18%, 8.16% and water demand by 1.45%, 1.68%, 2.36% under RCP 2.6, 4.5, and 8.5 scenarios by 2050s, respectively. As a result, climate change will, in general, have little impact on water stress in the B&R countries as a whole. However, climate change will make future water resources more unevenly distributed among the B&R countries and regions, exacerbating water stress in some countries, especially in Central Asia and West Asia. Our results are informative for water resource managers and policymakers in the B&R countries to make sustainable water management strategies under future climate change. [ABSTRACT FROM AUTHOR]

Climate change (CC) impacts on hydrology pose significant global concerns due to their effects on water availability, thereby impacting various human activities reliant on this essential resource. This study assesses the influence of CC on the water supply in the Angostura-Bolivia basin. We employed the RegCM4 system, which develops its own regional climate models (RCMs) tailored to the Angostura basin using specific convective schemes, diverging from reliance on pre-existing RCMs, like those provided by CORDEX. Methodologically, the study involves hydrometeorological data collection and analysis, utilizing dynamic and statistical downscaling methods to refine the RCMs derived from ERA-Interim reanalysis data. Subsequently, precipitation and temperature projections are generated under CC scenarios (RCP 4.5 and RCP 8.5) for both near (2045–2055) and far (2065–2075) future periods, compared to the historical period (1981–2010). The final stage employs the HydroBID system to project future runoff, considering both perturbed and unperturbed hydrometeorological data under CC effects. The analysis of flow duration curves for 50%, 75%, and 90% exceedance probabilities reveals a significant reduction in flows across all scenarios, indicating a noteworthy impact on water availability. These findings underscore the urgency of comprehending and adapting to CC on hydrology, emphasizing the critical importance of sustainable water resource management amidst evolving climatic conditions. [ABSTRACT FROM AUTHOR]

The Cantareira Water Production System (CWPS), which supplies water to the most populous region in Brazil, is facing significant challenges due to hydroclimate change, thus threatening its water security. This research integrates data from climate models and field observations with hydrological modeling, aimed at quantifying trends in key variables of the hydrological cycle. The GFDL-CM4 climate model, the most suitable for the study area, was employed to generate runoff data under both current conditions and future scenarios (SSP2-4.5 and SSP5-8.5). Our analysis reveals an increasing trend in the frequency of dry hydrological years. The Standard Precipitation Index (SPI) and Drought Magnitude (DM) confirm an increase in both the occurrence and duration of droughts in future scenarios. The runoff in all basins was reduced, causing a substantial decrease in minimum flows of 16.9%, medium flows of 11.8%, and high flows of 9.2% for the SSP5-8.5 scenario. This research introduces an approach to hydroclimate impact assessment, combining rigorous data analysis with advanced modeling techniques. Our findings not only provide a comprehensive understanding of the challenges faced by the CWPS, but also offer critical quantitative insights essential for developing effective public policies and adaptive strategies for sustainable water resource management. [ABSTRACT FROM AUTHOR]

The Hindu Kush Himalaya region in Nepal is considered hydrologically vulnerable and fragile, and is likely to face adverse impacts due to climate change. Many rivers originate in this region, which are the lifeline for the millions of riparian people. The Marsyangdi river basin is the hub of hydroelectric power generation. The main objective of this study is to assess the impact of climate change in water availability by using the Soil and Water Assessment Tool (SWAT) model. Future climate projections were derived from three regional climate models (RCMs), namely ACCESS1‐CCAM (ACCESS) CNRM‐CM5‐CCAM (CNRM), and MPI‐ESM‐LR‐CSIRO‐CCAM under two representative concentration pathways, RCP 4.5 and RCP 8.5. These projections were bias‐corrected against the observed historical data, and simulation of impact was assessed using the SWAT model. This study reveals an increase in maximum temperature by 1.4°C by the 2040s (2031–50) and 2.6°C by the 2070s (2061–80) and in minimum temperature by 1.8 and 2.9°C by the 2040s and 2070s, respectively. The future projected rainfall shows a declining trend in all the models. The maximum increase in annual rainfall in the CNRM model is about 31.1% for RCP 8.5 during the 2040s and the MPI RCP 8.5 model show a minimum reduction of about 19.6% in the 2070s. In all three models the average annual rainfall is expected to increase by 10.2 and 10.7% by the 2040s and 2070s respectively. The reduction in streamflow in 2031–2050 is maximally about 19% in the CNRM RCP 8.5 and minimally about 6.3% in the MPI RCP 8.5. For the period 2061–2080, the CNRM RCP 8.5 shows a maximum decrease in streamflow of about 18.9% and the MPI RCP 8.5 shows a minimum reduction in streamflow of about 2.6%. This study will give significant insight to the planners for sustainable and integrated management of water resources and for the operation and design of hydropower projects in the basin. [ABSTRACT FROM AUTHOR]

This study aims to evaluate the effect of climate change on water availability in the Bilate catchment, Southern Ethiopia. The bias-corrected outputs of five climate models and their ensemble mean were used for the baseline (1976-2005), the 2050s, and 2080s under Representative Concentration Pathways (RCP) for both RCP4.5 and RCP8.5 scenarios. A semi-distributed physically-based Hydrologic Engineering Center of Hydrologic Modeling System (HEC-HMS) was used to perform rainfall-runoff simulation after sensitivity analysis, calibration, and validation. The forecasted temperatures of the watershed will increase in the future. The forecasting from all the climate models indicated that rainfall of the watershed will increase by 34% in the 2050s and 21% in 2080s under RCP4.5 and RCP8.5 respectively. The discharge projection for almost all climate models shows an increment up to 27% whereas it will decline up to 30% under RCP 4.5 and RCP8.5 respectively in the 2050s. In the 2080s, nearly all climate models will show an increment up to 25% in discharge whereas it will decrease up to 32% under RCP4.5 and RCP8.5 respectively. This research paves the way to reduce the impacts of changing climate for sustainable water resources management. [ABSTRACT FROM AUTHOR]

Mediterranean countries are strongly affected by reduced surface water resources. This study aims to assess the climate change impacts on runoff supply to the Bin El Ouidane dam in Morocco, the largest in the country in terms of hydropower production. A water balance model coupled with a stochastic calibration method to provide confidence intervals on simulated discharge is used to reproduce discharge using observed and bias-corrected ECMWF Reanalysis 5th Generation (ERA5) rainfall (WFDE5). Five regional climate models from the EURO-CORDEX initiative are considered to estimate the climate change impacts on surface runoff for the Representative Concentration Pathway (RCP4.5) and RCP8.5 scenarios. Results indicate a future increase in evapotranspiration (+15 to +36%) associated with a decrease in precipitation (−16 to −34%) in both climate scenarios. The hydrological projections indicated a significant decrease in runoff (−57 to −86%), more severe when the model is driven by WFDE5 compared to observed precipitation. Consequently, the strong decline of surface water resources imply a change in water ressource management for hydropower production and local agriculture to adapt to the future climatic conditions. [ABSTRACT FROM AUTHOR]

South America contributes to roughly 30% of global runoff to the oceans. Because the regional economy and biodiversity depend significantly on its water resources, assessing potential climate change impacts on the continental water balance is crucial to support water management planning. Here we evaluate the mean alterations of water balance variables and river discharge in South America by the end of this century using two different GHG scenarios (RCP4.5 and RCP8.5). An ensemble comprising 25 global climate models (GCM) from CMIP5 is used to force a continental-scale hydrologic-hydrodynamic model developed for that region. A negative signal with respect to changes in precipitation, evapotranspiration, and runoff is observed on most of the continent. Major decreases in the annual mean discharge are expected for the Orinoco, Tocantins, and Amazon basins, which would be around 8–14% at least (statistically significant – RCP4.5 and RCP8.5, respectively). Only the Uruguay Basin presents a positive trend for the mean discharge. [ABSTRACT FROM AUTHOR]

The aim of this study is to assess the impacts of climate change on the water resources of Cyprus with special emphasis on water availability and to evaluate the capacity of the resource itself, as well as of the government and people in Cyprus to adapt to climate change. The methodology followed includes the recording of the baseline situation and the assessment of climate change impacts and vulnerabilities. For the assessment, climate projections produced by regional climate models were used. The climate change factors, which are considered to affect the water resources in Cyprus, refer to the increase in temperature, the decrease in precipitation as well as the increase in droughts and in heavy rainfall. For the impact assessment, the changes in river and groundwater flows as well as other WSIs were studied. For the adaptation assessment, the degree of freshwater and non-freshwater resources exploitation and the measures for water demand reduction and the enhancement of drought preparedness were examined. At first, priorities with regard to climate change vulnerability, the water availability for domestic water supply and irrigation in mountain areas and the water availability for irrigation in plain and coastal areas were identified, while water availability for domestic water supply was estimated to present limited vulnerability to climate change. [ABSTRACT FROM AUTHOR]

Climate change impact assessment is crucial for strategic planning in many areas, including water management, agriculture and forestry. Water planning has a long tradition in the Czech Republic, who has implemented the requirements of the Water Framework Directive since 2000. Following the expected impacts of climate change on the hydrological regime, adaptation measures in the water sector are being prepared as part of strategic plans. This contribution studies the uncertainty propagation of climate scenarios in hydrological data, which are then used to assess the reliability of water resources and to design appropriate adaptation measures. The results are being discussed for a case study in the deficit area of Rakovnický stream and Blšanska river basins, which are among the driest areas in the Czech Republic. Research of the impact of climate change on the reliability of water resources has been prepared using ensembles of selected regional climate models. This approach has allowed a probabilistic assessment of the impact on the hydrology regime and the reliability of water supply from reservoirs for various time horizons of climate change. In view of the relatively large variance of potential impacts on water resources, options for further strategic planning in the water management area are being discussed. [ABSTRACT FROM AUTHOR]

The future planning and management of water resources ought to be based on climate change projections at relevant temporal and spatial scales. This work uses the new regional demarcation for Southern Africa (SA) to investigate the spatio-temporal precipitation variability and trends of centennial-scale observation and modeled data, based on datasets from the sixth phase of the Coupled Model Intercomparison Project (CMIP6). The study employs several statistical methods to rank the models according to their precipitation simulation ability. The Theil–Sen slope estimator is used to assess precipitation trends, with a Student's t-test for the significance test. The comparison of observation and model historical data enables identification of the best-performing global climate models (GCMs), which are then employed in the projection analysis under two Shared Socioeconomic Pathways (SSPs): SSP2-4.5 and SSP5-8.5. The GCMs adequately capture the annual precipitation variation but with a general overestimation, especially over high-elevation areas. Most of the models fail to capture precipitation over the Lesotho-Eswatini area. The three best-performing GCMs over SA are FGOALS-g3, MPI-ESM1-2-HR and NorESM2-LM. The sub-regions demonstrate that precipitation trends cannot be generalized and that localized studies can provide more accurate findings. Overall, precipitation in the wet and dry seasons shows an initial increase during the near future over western and eastern SA, followed by a reduction in precipitation during the mid- and far future under both projection scenarios. Madagascar is expected to experience a decrease in precipitation amount throughout the twenty-first century. [ABSTRACT FROM AUTHOR]