Theme 1: Water Availability

The Bui hydropower plant plays a vital role in the socio-economic development of Ghana. This paper attempt to explore the combined effects of climate-land use land cover change on power production using the (WEAP) model: Water Evaluation and Planning system. The historical analysis of rainfall and stream flow variability showed that the annual coefficient of variation of rainfall and stream flow are, respectively, 8.6{\%} and 60.85{\%}. The stream flow varied greatly than the rainfall, due to land use land cover changes (LULC). In fact, the LULC analysis revealed important changes in vegetative areas and water bodies. The WEAP model evaluation showed that combined effects of LULC and climate change reduce water availability for all of demand sectors, including hydropower generation at the Bui hydropower plant. However, it was projected that Bui power production will increase by 40.7{\%} and 24.93{\%}, respectively, under wet and adaptation conditions, and decrease by 46{\%} and 2.5{\%}, respectively, under dry and current conditions. The wet condition is defined as an increase in rainfall by 14{\%}, the dry condition as the decrease in rainfall by 15{\%}; current account is business as usual, and the adaptation is as the efficient use of water for the period 2012–2040.

Potential implications of rainfall variability along with Land Use and Land Cover Change (LULC) on stream flow have been assessed in the Black Volta basin using the SWAT model. The spatio-temporal variability of rainfall over the Black Volta was assessed using the Mann-Kendall monotonic trend test and the Sen's slope for the period 1976–2011. The statistics of the trend test showed that 61.4{\%} of the rain gauges presented an increased precipitation trend whereas the rest of the stations showed a decreased trend. However, the test performed at the 95{\%} confidence interval level showed that the detected trends in the rainfall data were not statistically significant. Land use trends between the year 2000 and 2013 show that within thirteen years, land use classes like bare land, urban areas, water bodies, agricultural lands, deciduous forests and evergreen forests have increased respectively by 67.06{\%}, 33.22{\%}, 7.62{\%}, 29.66{\%}, 60.18{\%}, and 38.38{\%}. Only grass land has decreased by 44.54{\%} within this period. Changes in seasonal stream flow due to LULC were assessed by defining dry and wet seasons. The results showed that from year 2000 to year 2013, the dry season discharge has increased by 6{\%} whereas the discharge of wet season has increased by 1{\%}. The changes in stream flows components such us surface run-off (SURF{\_}Q), lateral flow (LAT{\_}Q) and ground water contribution to stream flow (GW{\_}Q) and also on evapotranspiration (ET) changes due to LULC was evaluated. The results showed that between the year 2000 and 2013, SURF{\_}Q and LAT{\_}Q have respectively increased by 27{\%} and 19{\%} while GW{\_}Q has decreased by 6{\%} while ET has increased by 4.59{\%}. The resultant effects are that the water yield to stream flow has increased by 4{\%}.

Climate change potential impacts are evaluated through the changes in the local and regional climate. However, Global and Regional Climate simulated outputs do not often capture these changes well, hampering their direct applicability. Impact studies using coarse resolution data require bias-correction of climate variables, a process that minimizes the discrepancy between observed and simulated climate variables. This study assessed climate projections in the Volta Basin using an ensemble of 4 Regional Climate Models under the Representative Concentration Pathways-RCPs 4.5 and 8.5 scenarios in the CORDEX-Africa datasets. These datasets were bias-corrected using the Climate Model data for hydrologic modeling tool (CMhyd) and 27-years of Climate Forecast System Reanalysis data. The performances of the ensemble bias-corrected precipitation ranged from 97-99%, 93-99%, 70-485mm, and-9-5% for R 2 , NSE, RMSE, and PBIAS respectively. TMAX bias-correction performances ranged from 65-99%, 27-99%, 0-4°C and-2-7% for R 2 , NSE, RMSE and PBIAS respectively. For TMIN, the performances ranged from 91-99%, 91-99%, 0-1°C and 0-1% for R 2 , NSE, RMSE and PBIAS respectively. The annual projected change in precipitation under RCP4.5 and 8.5 indicated a decrease in precipitation for the near (the 2020s), the mid-century (2050s), and the end far (2080s) with a relative increase from late November to January, a period currently part of dry season period in the Volta Basin. This suggests that the basin could expect a potential shift in the rainy season. The 12-month standard precipitation index suggests more frequent and longer drought periods in the future. Changes in annual mean monthly maximum temperature revealed an increase under all scenarios and throughout the century with an intensified increase by the end of the century under the higher CO 2 concentration scenario (RCP 8.5). The study showed that under RCP 4.5 and 8.5 scenarios, the Volta Basin will experience frequent drought and extreme precipitation events, warmer days, and nights temperatures although RCP 4.5 showed a relatively lower magnitude of these extremes. It is therefore important to emphasize the need for strong adaptation to preserve water resources, limit negative impacts on energy and agricultural production, and other ecosystems services in the Volta Basin.

Groundwater is the main available freshwater resource and therefore its use, management and sustainability are closely related to the Sustainable Development Goals (SDGs). However, Land Use Land Cover (LULC) and climate change are among the factors impacting groundwater recharge. The use of land-use and climate data in conjunction with hydrological models are valuable tools for assessing these impacts on river basins. This systematic review aimed at assessing the integrated modeling approach for evaluating hydrological processes and groundwater recharge based on LULC and climate change. The analysis is based on 200 peer-reviewed articles indexed in Scopus, and the Web of Science. Continuous research and the development of context-specific groundwater recharge models are essential to increase the long-term viability of water resources in any basin. The long-term impacts of natural and anthropogenic drivers on river basin interactions require integrating knowledge and modeling capabilities across biophysical responses, environmental problems, policies, economics, social, and data.

The northeast region of Côte d’Ivoire, where agriculture is the main economic activity, is potentially vulnerable to extreme climatic conditions. This study aims to make a comprehensive spatio-temporal analysis of trends in extreme indices related to precipitation and temperature for the Zanzan region of Côte d’Ivoire over the period of 1981–2020. The statistical significance of the calculated trends was assessed using the non-parametric Mann–Kendall test, while Sen’s slope estimation was used to define the amount of change. For extreme precipitations, the results showed a decreasing trend in annual total precipitations estimated at 112.37 mm and in daily precipitations intensity indices. Furthermore, the consecutive dry days’ index showed an increasing trend estimated at 18.67 days. Unlike the trends in precipitation extremes, which showed statistically non-significant trends, the trends in temperature extremes were mostly significant over the entire study area. The cold spells indices all show decreasing trends, while the warm spells show increasing trends. Drawing inferences from the results, it becomes clear that the study area may be threatened by food insecurity and water scarcity. The results are aimed to support climate adaptation efforts and policy intervention in the region.

Irrigation is important for food security, however, water requirements for sustainable irrigation may be affected by climate change. The study analysed water requirements of two commonly cultivated crops in the dry season in the Ghanaian Savannah regions under baseline and future periods. Crop water requirement (CWR) and crop irrigation requirement (CIR) were lowest in baseline periods and increased in the 2020s, 2050s, and 2080s for RCP 4.5 and RCP 8.5 at all locations. CIR was higher for tomato as compared to onions for most locations. Seasonal changes in the CWR ranged from 2-9, 3-12, and 3-12% and 2-8 3-12% and 5-18% for the 2020s, 2050s and 2080s under RCP 4.5 and RCP 8.5, respectively, for both the crops. Bole and Zuarungu recorded highest increases in CWR for tomato, whereas the least change was observed at Yendi for onions. Changes in seasonal CIR ranged from 3-19, 2-21, and 6-22%, respectively, for the 2020s, 2050s and 2080s for RCP 4.5. Under RCP 8.5, changes in seasonal CIR ranged from 3-23, 5-23, and 6-27% were observed for the 2020s, 2050s, and 2080s, respectively. Highest increases in CIR were noticed at Bole and Zuarungu for tomato, whereas the least change was observed at Wenchi for onions. Findings of the study support zero hunger and climate action, goals 2 and 13 of the Sustainable Development Goals (SDGs).

Irrigation is important for food security, however, water requirements for sustainable irrigation may be affected by climate change. The study analysed water requirements of two commonly cultivated crops in the dry season in the Ghanaian Savannah regions under baseline and future periods. Crop water requirement (CWR) and crop irrigation requirement (CIR) were lowest in baseline periods and increased in the 2020s, 2050s, and 2080s for RCP 4.5 and RCP 8.5 at all locations. CIR was higher for tomato as compared to onions for most locations. Seasonal changes in the CWR ranged from 2–9, 3–12, and 3–12% and 2–8 3–12% and 5–18% for the 2020s, 2050s and 2080s under RCP 4.5 and RCP 8.5, respectively, for both the crops. Bole and Zuarungu recorded highest increases in CWR for tomato, whereas the least change was observed at Yendi for onions. Changes in seasonal CIR ranged from 3–19, 2–21, and 6–22%, respectively, for the 2020s, 2050s and 2080s for RCP 4.5. Under RCP 8.5, changes in seasonal C...