Assessment of the impact of land use change and climate change on the hydropower potential of the Maziba catchment.

Abstract

Climate change and land use impact the hydrology of catchments in different ways. Catchment Management Interventions (CMIs) implemented in the Maziba region of western Uganda have brought about changes in land use in the catchment. The main objective of this study was to model the impact of land use change affected by CMIs and climate change on the hydropower reliability of River Maziba. Unsupervised classification of land use was done in ArcGIS. The changes in land use were assessed in the catchment which were attributed to CMIs between 2014-2022. Four land use/ land cover (LULC) classes were identified which include forests, vegetation, bare land and settlement. Results indicated that settlement registered the most significant increase by 79%. There was also an increase in forest cover by 10%. A reduction was registered in vegetation and bare land 13.6% and 33.6% respectively. Two downscaled Regional Climate Models (RCA4 and REMO2009) from the CORDEX datasets were used in this study to create future scenarios for precipitation under Representative Concentration Pathways (RCPs) 4.5 and 8.5. A calibrated HEC-HMS model was applied for the midcentury period (2041-2060) to simulate future stream flows. Flow duration curves were plotted and the firm flows (flow≥ 95% exceedance probability) were determined for the four scenarios under RCP 4.5 and RCP8.5. The future land use (2041) was projected using the CA Markov model in Idrisi Selva. The current hydropower generation capacity of River Maziba according to discharge exceeded 95% of the time is 756.13 kW. Two scenarios have been described in this study. One fixes land use and varies climatic scenarios. The hydropower reliability of the river obtained according to discharge exceeded 95% was 1075.67 kW (42% increase) under the most probable baseline scenario of a general temperature rise of 1.8oC by 2100 and 553.65 kW (27% reduction) under extreme scenario of carbon dioxide emissions three times higher than present with a general temperature rise of 3.7oC by 2100. The other varies land use changes with climatic conditions fixed. Changes in land use alone had no significant impact on the discharge. The study concludes that climate change affects stream flows more significantly than changes in land use.