Abstract
This article illustrates the impact of potential future climate scenarios on water quantity in time and space for an East African floodplain catchment surrounded by mountainous areas. In East Africa, agricultural intensification is shifting from upland cultivation into the wetlands due to year-round water availability and fertile soils. These advantageous agricultural conditions might be hampered through climate change impacts. Additionally, water-related risks, like droughts and flooding events, are likely to increase. Hence, this study investigates future climate patterns and their impact on water resources in one production cluster in Tanzania. To account for these changes, a regional climate model ensemble of the Coordinated Regional Downscaling Experiment (CORDEX) Africa project was analyzed to investigate changes in climatic patterns until 2060, according to the RCP4.5 (representative concentration pathways) and RCP8.5 scenarios. The semi-distributed Soil and Water Assessment Tool (SWAT) was utilized to analyze the impacts on water resources according to all scenarios. Modeling results indicate increasing temperatures, especially in the hot dry season, intensifying the distinctive features of the dry and rainy season. This consequently aggravates hydrological extremes, such as more-pronounced flooding and decreasing low flows. Overall, annual averages of water yield and surface runoff increase up to 61.6% and 67.8%, respectively, within the bias-corrected scenario simulations, compared to the historical simulations. However, changes in precipitation among the analyzed scenarios vary between −8.3% and +22.5% of the annual averages. Hydrological modeling results also show heterogeneous spatial patterns inside the catchment. These spatio-temporal patterns indicate the possibility of an aggravation for severe floods in wet seasons, as well as an increasing drought risk in dry seasons across the scenario simulations. Apart from that, the discharge peak, which is crucial for the flood recession agriculture in the floodplain, is likely to shift from April to May from the 2020s onwards.
Highlights
Wetlands in East Africa cover an area of approximately 180,000 km2 [1,2] and a share of about 10%of the land surface in Tanzania, numbers vary regarding this [3]
These study results show that in addition to climate change analyses, manifold factors are influencing the hydrology within the catchment [75]
The study clearly showed the broad range of possible future climate scenarios for the Kilombero
Summary
Wetlands in East Africa cover an area of approximately 180,000 km2 [1,2] and a share of about 10%of the land surface in Tanzania, numbers vary regarding this [3]. East African wetlands are endangered due to anthropogenic activities [6] This pressure is driven by several push factors, such as population growth, degradation of upland soils, and increasing rainfall variability due to climate change. Wetlands have relatively fertile soils in combination with year-round water availability as pull factors for the conversion of wetlands into cropland [7,8,9,10,11]. This conversion in favor of food production has negative trade-off effects on other ecosystem services
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