Browsing by Author "Dotse, Sam-Quarcoo"

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    Impact of climate change on groundwater recharge in the lake Manyara catchment, Tanzania
    (Elsevier, 2021-12-15) Nyemboa, Latifa; Larbi, Isaac; Mwabumbaa, Mohamed; Selemani, Juma; Dotse, Sam-Quarcoo; Limantol, Andrew; Bessah, Enoch
    Groundwater account for about 60 to 80% of water supply to the population of Tanzania's semi-arid regions for domestic and agriculture uses. Despite the importance of groundwater resource in semi-arid areas, limited information exists on the recharge amount and potential recharge zones in Tanzania in the context of climate change which could result in unsustainable withdrawals. This study aimed to estimate the potential impact of climate change on groundwater recharge and identify potential recharge zones in the Lake Manyara catchment using Water and Energy Transfer between Soil, Plants and Atmosphere under the quasi-steady State (WetSpass) model. The WetSpass model was setup and calibrated using hydro-meteorological data (rainfall, temperature, wind speed, potential evapotranspiration, and groundwater depth) and biophysical data (soil, land use, topography, and slope). Simulated rainfall, temperature and potential evapotranspiration from an ensemble of four CORDEX-Africa regional climate models for the period 2021–2050 under the Representative Concentration Pathway (RCP 8.5) scenario (hereafter referred as business-as-usual scenario) were used as input in the WetSpass model for the climate change impact assessment. WetSpass model calibration using the water balance equation showed a coefficient of determination (R2) value of 0.9 and Root-Mean-Square Error (RMSE) of 0.49 mm/yr between the simulated and calculated recharge. It was determined that the mean annual recharge of 53.9 mm/year (149 MCM/year) for the period 1989–2018 would increase by 7.9% in the future (2021–2050) under the business-as-usual climate scenario, due to the increase in rainfall. Seasonality and spatial differences in recharge amount were observed, with recharge projected to increase in the dry season and at areas that receive high amount of rainfall. Potential recharge zones in the catchment were found mostly around the northern part near Ngorongoro, the south-western part, and around Mbulu region. Findings from this study would help policymakers, and local stakeholders in planning and management of the groundwater resources for sustainable development.
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    Rainfall and temperature changes under different climate scenarios at the watersheds surrounding the Ngorongoro Conservation Area in Tanzania
    (Elsevier, 2022-04) Mwabumba, Mohamed; Yadav, Brijesh; Rwiza, Mwemezi; Larbi, Isaac; Dotse, Sam-Quarcoo; Manoba, Andrew; Sarpong, Solomon; Kwawuvi, Daniel
    Considering the high vulnerability of Northern Tanzania to climate change, an in-depth assessment at the local scale is required urgently to formulate sustainable adaptations measures. Therefore, this study analyzed the fu- ture (2021-2050) changes in rainfall and temperature under the representative concentration pathways (RCP4.5 and RCP8.5) for the watersheds surrounding the Ngorongoro Conservation Area (NCA) at a spatio-temporal scale relative to the observed historical (1982-2011) period. The climate change analysis was performed at monthly and annual scale using outputs from a multi-model ensemble of Regional Climate Models (RCMs) and statistically downscaled Global Climate Models (GCMs). The performance of the RCMs were evaluated, and the downscaling of the GCMs were performed using Statistical Downscaling System Model (SDSM) and LARS-WG, with all the models indicating a higher accuracy at monthly scale when evaluated using statistical indicators such as corre- lation (r), Nash-Sutcliff Efficiency (NSE) and percentage bias (PBIAS). The results show an increase in the mean annual rainfall and temperature in both RCPs. The percentage change in rainfall indicated an increase relative to historical data for all seasons under both RCPs, except for the June, July, August and September (JJAS) season, which showed a decrease in rainfall. Spatially, rainfall would increase over the entire basin under both RCPs with higher increase under RCP4.5. Similar spatial increase results are also projected for temperature under both RCPs. The results of this study provide vital information for the planning and management of the studied watershed under changing climatic conditions.