Forecasting Future Volta River System Discharges: Evaluating the Influence of Climate Change and Socio-Economic Shifts

As the scientific consensus concerning global climate change has increased in recent decades, research on the potential impacts of climate change on water resources has been given high importance. However, in Sub-Saharan Africa, few studies have fully evaluated the potential implications of climate change on its water resource systems. The Volta River is one of the major rivers in Africa, covering six riparian countries (mainly Ghana and Burkina Faso). It is a principal water source for approximately 24 million people in the region. The catchment is primarily agricultural, providing food supplies to rural areas, demonstrating the classic water, food, energy nexus. In this study, an Integrated Catchment Model (INCA) was applied to the whole Volta River system to simulate flow in the rivers and at the outlet of the artificial Lake Volta. High-resolution climate scenarios downscaled from three different Global Climate Models (CNRM-CM5, HadGEM2-ES and CanESM2) as part of the CORDEX Africa project were used to drive the INCA model and to assess changes in flow by the 2050s and 2090s under the high climate forcing scenario RCP8.5. The results showed that peak flows during the monsoon months could increase into the future, although the downscaled HadGEM2-ES scenario indicated a decreasing trend by the 2090s. The duration of high flow could become longer compared to the recent condition. In addition, we considered three different socio-economic scenarios for the Volta River Basin, which make different assumptions about population growth and increases in the area of agricultural land use. However, the effects of changing socio-economic conditions on flow are minor compared to the climate change impact. Under the combined impact from climate change (CNRM-CM5) and medium+ socio-economic changes, the extreme high flow (Q5) of Black Volta River is projected to increase 11% and 36% at the 2050s and 2090s, respectively. Lake Volta outflow would increase +1% and +5% at the 2050s and 2090s, respectively. These results provide valuable information assisting future water resource development and adaptive strategies in the Volta Basin.