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Although Ghana is a leading global cocoa producer, its production and yield have experienced declines in recent years due to various factors, including long-term climate change such as increasing temperatures and changing rainfall patterns, as well as drought events. With the increasing exposure of cocoa-producing regions to extreme weather events, the vulnerability of cocoa production is also expected to rise. Supplemental irrigation for cocoa farmers has emerged as a viable adaptation strategy to ensure a consistent water supply and enhance yield. However, understanding the potential for surface and groundwater irrigation in the cocoa-growing belt remains limited. Consequently, this study aims to provide decision-support maps for surface and groundwater irrigation potential to aid planning and investment in climate-smart cocoa irrigation. Utilizing state-of-the-art geospatial and remote sensing tools, data, and methods, alongside in-situ groundwater data, we assess the irrigation potential within Ghana's cocoa-growing areas. Our analysis identified a total area of 22,126 km 2 for cocoa plantations and 125.2 km 2 for surface water bodies within the cocoa-growing regions. The multi-criteria analysis (MCA) revealed that approximately 80% of the study area exhibits moderate to very high groundwater availability potential. Comparing the MCA output with existing borehole locations demonstrated a reasonable correlation, with about 80% of existing boreholes located in areas with moderate to very high potential. Boreholes in very high potential areas had the highest mean yield of 90.7 l/min, while those in low groundwater availability potential areas registered the lowest mean yield of 58.2 l/min. Our study offers a comprehensive evaluation of water storage components and their implications for cocoa irrigation in Ghana. While groundwater availability shows a generally positive trend, soil moisture and surface water have been declining, particularly in the last decade. These findings underline the need for climate-smart cocoa irrigation strategies that make use of abundant groundwater resources during deficit periods. A balanced conjunctive use of surface and groundwater resources could thus serve as a sustainable solution for maintaining cocoa production in the face of climate change.

This study evaluates the ability of different gridded rainfall datasets to plausibly represent the spatio-temporal patterns of multiple hydrological processes (i.e. streamflow, actual evaporation, soil moisture and terrestrial water storage) for large-scale hydrological modelling in the predominantly semi-arid Volta River basin (VRB) in West Africa. Seventeen precipitation products based essentially on gauge-corrected satellite data (TAMSAT, CHIRPS, ARC, RFE, MSWEP, GSMaP, PERSIANN-CDR, CMORPH-CRT, TRMM 3B42 and TRMM 3B42RT) and on reanalysis (ERA5, PGF, EWEMBI, WFDEI-GPCC, WFDEI-CRU, MERRA-2 and JRA-55) are compared as input for the fully distributed mesoscale Hydrologic Model (mHM). To assess the model sensitivity to meteorological forcing during rainfall partitioning into evaporation and runoff, six different temperature reanalysis datasets are used in combination with the precipitation datasets, which results in evaluating 102 combinations of rainfall–temperature input data. The model is recalibrated for each of the 102 input combinations, and the model responses are evaluated by using in situ streamflow data and satellite remote-sensing datasets from GLEAM evaporation, ESA CCI soil moisture and GRACE terrestrial water storage. A bias-insensitive metric is used to assess the impact of meteorological forcing on the simulation of the spatial patterns of hydrological processes. The results of the process-based evaluation show that the rainfall datasets have contrasting performances across the four climatic zones present in the VRB. The top three best-performing rainfall datasets are TAMSAT, CHIRPS and PERSIANN-CDR for streamflow; ARC, RFE and CMORPH-CRT for terrestrial water storage; MERRA-2, EWEMBI/WFDEI-GPCC and PGF for the temporal dynamics of soil moisture; MSWEP, TAMSAT and ARC for the spatial patterns of soil moisture; ARC, RFE and GSMaP-std for the temporal dynamics of actual evaporation; and MSWEP, TAMSAT and MERRA-2 for the spatial patterns of actual evaporation. No single rainfall or temperature dataset consistently ranks first in reproducing the spatio-temporal variability of all hydrological processes. A dataset that is best in reproducing the temporal dynamics is not necessarily the best for the spatial patterns. In addition, the results suggest that there is more uncertainty in representing the spatial patterns of hydrological processes than their temporal dynamics. Finally, some region-tailored datasets outperform the global datasets, thereby stressing the necessity and importance of regional evaluation studies for satellite and reanalysis meteorological datasets, which are increasingly becoming an alternative to in situ measurements in data-scarce regions.

Whilst substantial efforts have been deployed to understand the “Sahel hydrological paradox”, most of the studies focused on small experimental watersheds around the central and western Sahel. To our knowledge, there is no study on this issue covering all the watersheds located within the Sahelian belt. The absence of relevant studies may be attributed to a sparsity of in situ data leading to a dearth of knowledge on the Sahel hydrology. To fill this knowledge gap, the present study leverages analytical methods and freely available geospatial datasets to understand the effects of climatic factors, soil moisture and vegetation cover changes on surface runoff in 45 watersheds located within the Sahelian belt over two decades (2000–2021). Analyses show increasing trends in annual precipitation and potential evapotranspiration (PET) in more than 80% of the watersheds. Surface runoff, soil moisture (SM), and vegetation cover measured using the normalised difference vegetation index (NDVI) also show increasing trends in all the watersheds. Multivariable linear regression (MLR) analyses reveal that precipitation, PET, SM, and NDVI contribute about 62% of surface runoff variance. Further analyses using MLR, and the partial least squares regression (PLSR) show that precipitation and NDVI are the main factors influencing surface runoff in the Sahel. Elasticity coefficients reveal that a 10% increase in precipitation, SM and NDVI may lead to about 22%, 26% and 45% increase in surface runoff respectively. In contrast, a 10% increase in PET may lead to a 61% decline in surface runoff in the Sahel. This is the first hydrological study covering all the watersheds located within the Sahelian belt with results showing that surface runoff is influenced by climate, SM and NDVI to varying degrees. Given the unique hydrological characteristics of the Sahel, a better understanding of the different factors influencing surface runoff may be crucial for enhancing climate adaptation and ecological restoration efforts in the region such as the Great Green Wall Initiative.

A comprehensive evaluation of the impacts of climate change on water resources of the West Africa Volta River basin is conducted in this study, as the region is expected to be hardest hit by global warming. A large ensemble of 12 general circulation models (GCMs) from the fifth Coupled Model Intercomparison Project (CMIP5) that are dynamically downscaled by five regional climate models (RCMs) from the Coordinated Regional-climate Downscaling Experiment (CORDEX)-Africa is used. In total, 43 RCM–GCM combinations are considered under three representative concentration pathways (RCP2.6, RCP4.5, and RCP8.5). The reliability of each of the climate datasets is first evaluated with satellite and reanalysis reference datasets. Subsequently, the Rank Resampling for Distributions and Dependences (R2D2) multivariate bias correction method is applied to the climate datasets. The bias-corrected climate projections are then used as input to the mesoscale Hydrologic Model (mHM) for hydrological projections over the 21st century (1991–2100). Results reveal contrasting dynamics in the seasonality of rainfall, depending on the selected greenhouse gas emission scenarios and the future projection periods. Although air temperature and potential evaporation increase under all RCPs, an increase in the magnitude of all hydrological variables (actual evaporation, total runoff, groundwater recharge, soil moisture, and terrestrial water storage) is only projected under RCP8.5. High- and low-flow analysis suggests an increased flood risk under RCP8.5, particularly in the Black Volta, while hydrological droughts would be recurrent under RCP2.6 and RCP4.5, particularly in the White Volta. The evolutions of streamflow indicate a future delay in the date of occurrence of low flows up to 11 d under RCP8.5, while high flows could occur 6 d earlier (RCP2.6) or 5 d later (RCP8.5), as compared to the historical period. Disparities are observed in the spatial patterns of hydroclimatic variables across climatic zones, with higher warming in the Sahelian zone. Therefore, climate change would have severe implications for future water availability with concerns for rain-fed agriculture, thereby weakening the water–energy–food security nexus and amplifying the vulnerability of the local population. The variability between climate models highlights uncertainties in the projections and indicates a need to better represent complex climate features in regional models. These findings could serve as a guideline for both the scientific community to improve climate change projections and for decision-makers to elaborate adaptation and mitigation strategies to cope with the consequences of climate change and strengthen regional socioeconomic development.

In July 2021, Typhoon In‐Fa produced record‐breaking extreme precipitation events (hereafter referred to as the 2021 EPEs) in central and eastern China, and caused serious socioeconomic losses and casualties. However, it is still unknown whether the 2021 EPEs can be attributed to anthropogenic climate change (ACC) and how the occurrence probabilities of precipitation events of a similar magnitude might evolve in the future. The 2021 EPEs in central (eastern) China occurred in the context of no linear trend (a significantly increasing trend at a rate of 4.44%/decade) in the region‐averaged Rx5day (summer maximum 5‐day accumulated precipitation) percentage precipitation anomaly (PPA), indicating that global warming might have no impact on the 2021 EPE in central China but might have impacted the 2021 EPE in eastern China by increasing the long‐term trend of EPEs. Using the scaled generalized extreme value distribution, we detected a slightly negative (significantly positive) association of the Rx5day PPA time series in central (eastern) China with the global mean temperature anomaly, suggesting that global warming might have no (a detectable) contribution to the changes in occurrence probability of precipitation extremes like the 2021 EPEs in central (eastern) China. Historical attributions (1961–2020) showed that the likelihood of the 2021 EPE in central/eastern China decreased/increased by approximately +47% (−23% to +89%)/+55% (−45% to +201%) due to ACC. By the end of the 21st century, the likelihood of precipitation extremes similar to the 2021 EPE in central/eastern China under SSP585 is 14 (9–19)/15 (9–20) times higher than under historical climate conditions. Plain Language Summary Central and eastern China experienced record‐breaking extreme precipitation events (EPEs) in July 2021. The summer maximum 5‐day accumulated precipitation (Rx5day) of the 2021 EPE in central (eastern) China exceeded the climatology during 1981–2010 by 116.8% (96.1%). Under climate conditions of 1961 and 2021 and based on observations, the 2021 EPE was estimated to be a 1‐in‐76‐year event and 1‐in‐212‐year event in central China, respectively, and a 1‐in‐>10,000‐year and a 1‐in‐256‐year event in eastern China, respectively. Here, we estimate the contribution of anthropogenic climate change (ACC) to precipitation extremes of a similar magnitude to the 2021 EPEs and project how their probability might change in the future, based on climate projections from Coupled Model Intercomparison Project Phase 6. We estimate that ACC is responsible for +47%/+55% of the decrease/increase in the occurrence probability of the 2021 EPE in central/eastern China. By the end of the 21st century under a high emission scenario, the probability of occurrence of precipitation extremes similar to the 2021 EPE in central/eastern China is projected to be 14/15 times larger than under historical climate conditions. Our results highlight that EPEs in central and eastern China are becoming more frequent and more extreme in response to increasing greenhouse gas emissions. Key Points Global warming might have no (a detectable) contribution to the occurrence probability of a precipitation extreme like the 2021 extreme precipitation event (EPE) in central (eastern) China Anthropogenic climate change contributed to +47%/+55% of the decrease/increase in the occurrence probability of the 2021 EPE in central/eastern China By the end of the 21st century, the likelihood of such event in central/eastern China would be increased by 14/15 times under SSP585

High air temperatures and low atmospheric humidity can result in severe disasters such as flash droughts in regions characterized by high humidity (monsoon regions). However, it remains unclear whether responses of hot extremes to warming temperature are amplified on dry days as well as the response of dry extremes on hot days. Here, taking eastern monsoon China (EMC) as a typical monsoon region, we find a faster increase in air temperature on drier summer days, and a faster decrease in atmospheric humidity on hotter days, indicating “hotter days get drier” and “drier days get hotter” (i.e., coupling hotter and drier extremes), especially in southern EMC. The southern EMC is also a hotspot where the coupling hot‐dry extremes has become significantly stronger during the past six decades. The stronger hot‐dry coupling in southern EMC is associated with anomalies in large‐scale circulations, such as reduced total cloud cover, abnormal anticyclones in the upper atmosphere, intense descending motion, and strong moisture divergence over this region. Land‐atmosphere feedback enhance the hot‐dry coupling in southern EMC by increasing land surface dryness (seen as a decrease in the evaporation fraction). The decreasing evaporation fraction is associated with drying surface soil moisture, controlled by decreases in pre‐summer 1‐m soil moisture and summer‐mean precipitation. Given hot extremes are projected to increase and atmospheric humidity is predicted to decrease in the future, it is very likely that increasing hot‐dry days and associated disasters will be witnessed in monsoon regions, which should be mitigated against by adopting adaptive measures. Plain Language Summary High air temperatures (i.e., hot extremes) and low atmospheric humidity (i.e., dry extremes) are regarded as important metrics affecting human society and the environment in monsoon regions, including food production and natural disasters. Our results show that over eastern monsoon China (EMC), positive responses of hot extremes to warming temperature are magnified on dry days, at the same time, negative responses of dry extremes to warming temperature are enhanced on hot days. In other words, the warming rates of hot extremes per 1°C warming are fastest on dries days, meanwhile, the drying rates of dry extremes per 1°C warming are fastest on hottest days, especially in southern EMC. The southern EMC is also a hotspot where more hot or dry days have become hot‐dry days (i.e., stronger coupling of hot and dry extremes) during the past six decades. This stronger coupling of hot and dry extremes can be explained by anomalous large‐scale circulations and land‐atmosphere feedbacks in southern EMC. Our findings suggest that the positive coupling of hotter and drier extremes should be taken into consideration, and adaptive measures are required to mitigate adverse effects of hot and dry extremes. Key Points Positive (negative) responses of hot (dry) extremes to warming temperature are amplified on dry (hot) days over eastern monsoon China Coupling of hot and dry extremes has strengthened in past six decades in southern EMC Coupling of hotter and drier extremes can be explained by anomalies of large‐scale circulations and land‐atmosphere feedbacks

Cocoa production in Ghana faces challenges from climate change and land use dynamics, necessitating sustainable intensification through supplemental irrigation. However, the availability of water resources for irrigation remains underexplored in Ghana’s agroforestry landscapes. This study assesses the potential of water resources for irrigation and impacts of land use and climate changes in the moist semi-deciduous agroforestry-dominated Upper Offin basin. Using Landsat images, the study analyzed land use patterns, hydro-climatic trends (1981–2022), and water balance based on rainfall and evapotranspiration. Findings reveal that streamflow represents only 10% of average annual rainfall (1333 mm), with subsurface flow predominating. Annual actual evapotranspiration (AET) accounts for 85% of rainfall, while deep percolation offers additional water potential. Shallow groundwater could irrigate 10% of the area during the 5-month dry season, doubling with deep percolation. Land use changes threaten this potential, as forest areas declined while cropland and grassland expanded (2008–2021), associated highly with the alteration of water balance components. Although rainfall remained stable, rising temperatures could increase cocoa water demand. AET declined over time, correlating with FAO-WaPOR data, while streamflow increased during the observed period (1986–2012). The study recommends groundwater supplemental irrigation systems for sustainable cocoa farming in Ghana and similar agroforestry regions, addressing climate and land use challenges effectively.

Climate change effects are expected to be profoundly local and region-specific, underlining the urgent need for local-level assessments. This study emphasizes the agriculturally important Zanzan region of northeastern Côte d'Ivoire and examines future changes in precipitation, temperature, and resultant drought conditions based on six global climate models (GCMs) from the Coupled Model Intercomparison Project 6 (CMIP6) under shared socioeconomic pathways (SSPs) scenarios - SSP2-4.5 and SSP5-8.5. We integrate data from 12 stations within the Zanzan region, applying CMhyd software to correct model biases. Key statistical metrics confirm the well-calibrated nature of the corrected GCMs vis-à-vis observed data. Projections show a decrease in annual precipitation by an average of 133 mm and 177 mm under SSP2-4.5 and SSP5-8.5 scenarios respectively by 2100. Future precipitation patterns suggest a shift towards the prevalent dry season. Tmax and Tmin are projected to increase by +3 °C and +4.8 °C (SSP2-4.5 and SSP5-8.5) and +3.3 °C (both scenarios) respectively, by the end of the century. These changes suggest an intensification of severe droughts, particularly in the 2050s and 2080s, as assessed by the SPEI. Additionally, extreme temperatures (TX90p) and consecutive dry days (CDD) are projected to intensify, posing imminent threats to food security, water resources, and public health in the Zanzan region. This study bridges a critical gap by offering localized insights into future climate scenarios, thereby enhancing our understanding of the region-specific impacts of climate change. The research also underscores the urgency of adaptation and mitigation strategies tailored to the Zanzan region's vulnerabilities.

The upper Bandama basin at Badikaha in the North of Côte d'Ivoire, subject to climate change, has recorded a rapid population growth that significantly affects water availability. This study applies the water evaluation and planning (WEAP) system model to explore how the water resources available currently can meet people's needs in the future, mainly for irrigation, mining activities, rural and urban water supply and cattle breeding. The outputs from two regional climate models RACMO 22T and CCLM 4-8-17 under representative concentration pathway (RCP) 4.5 and RCP 8.5 scenarios were used for the climate change impact assessment. Results predict an increase in mean annual temperature by 1.5°C while precipitation could decrease by 21% by 2090. The climate model outputs coupled with the WEAP model show that unmet water demand estimated to 50 million m3 in 2020 could reach 115 million m3 in 2050. Nevertheless, climate change mitigation scenarios by the WEAP model, including the implementation of dams, boreholes and the hydraulics infrastructure improvement reveal that water scarcity could be reduced significantly in the catchment.

Climate change effects are expected to be profoundly local and region-specific, underlining the urgent need for local-level assessments. This study emphasizes the agriculturally important Zanzan region of northeastern Côte d’Ivoire and examines future changes in precipitation, temperature, and resultant drought conditions based on six global climate models (GCMs) from the Coupled Model Intercomparison Project 6 (CMIP6) under shared socioeconomic pathways (SSPs) scenarios - SSP2-4.5 and SSP5-8.5. We integrate data from 12 stations within the Zanzan region, applying CMhyd software to correct model biases. Key statistical metrics confirm the well-calibrated nature of the corrected GCMs vis-à-vis observed data. Projections show a decrease in annual precipitation by an average of 133 mm and 177 mm under SSP2-4.5 and SSP5-8.5 scenarios respectively by 2100. Future precipitation patterns suggest a shift towards the prevalent dry season. Tmax and Tmin are projected to increase by +3 °C and +4.8 °C (SSP2-4.5 and SSP5-8.5) and +3.3 °C (both scenarios) respectively, by the end of the century. These changes suggest an intensification of severe droughts, particularly in the 2050s and 2080s, as assessed by the SPEI. Additionally, extreme temperatures (TX90p) and consecutive dry days (CDD) are projected to intensify, posing imminent threats to food security, water resources, and public health in the Zanzan region. This study bridges a critical gap by offering localized insights into future climate scenarios, thereby enhancing our understanding of the region-specific impacts of climate change. The research also underscores the urgency of adaptation and mitigation strategies tailored to the Zanzan region’s vulnerabilities.