ASSESSING THE RESPONSE OF HYDROLOGICAL PROCESSES TO CLIMATE CHANGE IN THE PRA RIVER BASIN, GHANA
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ABSTRACT The Pra River Basin (PRB), Ghana, provides significant agricultural productivity and ecosystem services to Ghana. The challenge in water management within the PRB is constantly becoming a topical issue owing to the influence of increased climate change. Also, recent scenarios in climate variability have resulted in changing temperature and rainfall pattern thereby threatening water resource in three dams that source its water from the river basin. This has also negatively impacted river flow attributable to high rate of pollution, increased runoff, and high evaporation. It is therefore important to have an understanding of the consequence of variation in climate change on current and future hydrologic regimes and hydrologic extreme events through modelling approach. Hence, this research investigated the response of hydrological processes and hydrologic extremes in relation to climate change in the River Pra Basin by employing five (5) new Coupled Model Intercomparison Project (CMIP6) GCM for two time slices, near future (2030s) and mid future (2050s) under two emission SSP2-4.5 and SSP5-8.5 scenarios. Preliminary analysis revealed bias-corrected CNRM-CM6-1 (with linear scaling technique for precipitation and distribution mapping approach for temperature) as the best suitable climate model for climate change projection and further assessment of climate change impacts on streamflow and hydrologic extremes. SWAT model calibrated and validated data results compared with observed flow data were deemed satisfactory for future flow simulations over the Pra Basin. The change in projected monthly CNRM-CM6-1 precipitation data show variable temporal trends ranging between 2.84-5.74 mm under both SSP2-4.5 and SSP5-8.5 and with a more seasonal variation in change in precipitation projected under SSP5-8.5. Also, a continuous increasing trend is observed for mean projected temperature under SSP2-4.5 and SSP5-8.5 scenarios. The mean flow by the end of the middle of 21st century was projected to decrease at about 20.8% under SSP2-4.5 and 28.2% under SSP5-8.5 relative to the baseline period. Also, all seasons showed a decrease in annual seasonal discharge for the period of 2045 to 2074. Finally, the analysis of hydrologic flow regimes for extreme streamflow assessment revealed that the variability and magnitude of floods may increase in the near future due to increase in Q1(13.5%) and Q5 (5.4%) under SSP5. Hence flood mitigation measures as well as proper water resources management strategies must be ensured by stakeholders through the implementation of the PRB IWRM plan to avoid any catastrophes downstream of the basin.
- Nexus: Water-Climate