Impact of Climate Change on Water Resources in Rwanda: A Case of Muvumba Catchment

Abstract

Climate change profoundly impacts water resources, affecting people's well-being, agriculture, industry, and urban development due to altered weather patterns. This study focuses on Rwanda's Muvumba catchment, aiming to assess climate change effects. Analyzing global (World Clim, GCMs, CMIP6) and national data sets, remote sensing (SRTM elevation data, DEM) generated insights on precipitation, evaporation, and temperature changes during 2012-2021 and projected 2021-2040. Employing GIS, HEC-HMS model, and remote sensing, a hydrological model evaluates Muvumba catchment's river discharge, informing effective implementation of mitigation and adaptation strategies. Analysis indicated fluctuating minimum temperatures (14°C to 17°C) and maximum annual temperatures (27°C to 28.3°C) in 2012-2021, with a 0.4°C rise in maximum temperature over the decade. Averaging 21.6°C to 22.5°C, increased evaporation heightened water body depletion, impacting Muvumba catchment's water availability, exacerbating drought and scarcity. Projections for 2021-2040 anticipate March at 15.01°C as the coldest month, while July hits 28.7°C. Mean temperature may range from 21°C to 23.3°C, with a projected 0.82°C increase. Notably, annual precipitation peaked in 2020 at 1176.31 mm and hit a low in 2017 with 628.77 mm, emphasizing the water stress issue. It was found that the impacted location was the Mulindi sub-catchment, which is susceptible to floods and soil erosion, with the silt end up as sediments in rivers and streams. Research indicated the prediction of 1033.68mm annual rainfall in 2012-2040. Over 20 years it is predicted the reduction of 18.76 mm of precipitation, the highest annual evaporation rate was 2013, indicated 3.83mm which led to more water lost from water bodies. From2012 to 2021 water quality level was varied between 7.6 pH and 7.35 pH which facilitated the release of toxic substances from sediments into water further impacting water quality. Future water demand and use scenarios show that water stress in Muvumba will gradually increase, river discharges reduced by 2019 and 2020 due to decreased precipitation, LULCCD showed reduction of 17% of forests which lead to high rises of temperature .The average monthly discharge is projected to decrease from June to August (Long dry season) by variation of 4.7 and 7.8%by 2021-2040. Large increase of stream flow is projected to occur in April and May by variation of 13 and 14.7%. The research recommended the upgrading and maintaining existing stations and calibrating meteorological instruments, including weather radar, to give all climate information required for future observing, climate trend detection, climate variability management, afforestation, early warning, and disaster management. Keyword: Climate change, Hydrological Modeling, Temperature, Precipitation, Evaporation and Water resources, Rwanda