Hydrologic responses to climate and land use/cover changes in world heritage site of Ngorongoro conservation area and surrounding catchments, northern Tanzania

Abstract

In Tanzania, various studies have analyzed the impact of climate and land use/cover changes on water resources. However, information on the interactions between climate and land use/cover change, temporal and spatial variability of hydrological components and water quality at the local scale is insufficient. The objective of this study was to evaluate the hydrological response to climate and land use/cover changes in Ngorongoro Conservation Area (NCA) and surroundings. The study performed climate change analysis using outputs from a multi-model ensemble of Regional Climate Models (RCMs) and statistically downscaled Global Climate Models (GCMs). The CA–Markov model applied to project Land use/cover for the future 2025 and 2035. This study further used the Soil Water Assessment Tool (SWAT) modelling approaches to analyse the hydrological responses and HYDRUS 1D to determine the change in Groundwater quality due to climate and land use/cover changes. The analysis of climate change between historical period (1982-2011) and future period (2021-2050) indicated an increase in the mean annual rainfall and temperature, seasonal rainfall except June to September (JJAS) season which showed a decreasing trend. Spatially, rainfall and temperatures would increase over the entire area. The projected Land use/cover change for the period 2025 to 2035 compared to the baseline 2016, showed a reduction in bushland, forest, water, and woodland, but an intensification in cultivated land, grassland, bare land, and the built-up area. The surface runoff, evapotranspiration, lateral flow, and water yield would significantly increase in the future, while groundwater would decrease under combined climate and land use/cover change. It is predicted that two anions (Cl− and PO4 −3 ) and two cations (Na+ and K+ ) would exceed the permissible limits for the drinking water set by the World Health organisation (WHO) and Tanzania Bureau of Standards (TBS), from 2036 to 2050. Changes in groundwater quality due to major cations and anions is significantly correlated to evapotranspiration and temperature with Pearson correlation (r) between 0.35 and 0.85. Furthermore, correlate to the changes in all land use/ cover types with Pearson correlation (r) between 0.56 and 0.96. The results obtained provide further insight into future water resources management planning and adaptation strategie