Impacts of Climate Variability on Hydrological Response and Water Resources: Case of Little Ruaha Catchment -Tanzania Using Ground and CHIRPS Data

The Little Ruaha River catchment in Tanzania is increasingly affected by climate variability, with implications for agriculture, hydropower, and water supply. This study evaluates the effects of climate variability on rainfall and streamflow and assesses the usefulness of satellite-based rainfall data for hydrological modeling. Thirty-year records (1991–2020) of rain gauge and river flow data were analyzed using the Mann–Kendall test, and the HBV rainfall–runoff model was run with both gauge and CHIRPS satellite rainfall inputs. Annual rainfall exhibited no significant trends at most stations (p > 0.05), except for a notable decline at one eastern site. Seasonal rainfall and streamflow showed high interannual variability, ranging from ~1088 mm in the wettest season to ~458 mm in the driest. CHIRPS rainfall correlated strongly with observations (r > 0.85 monthly) and reproduced streamflow patterns for normal and low-flow conditions, but it underestimated extreme rainfall events, leading to peak flow under-prediction of about 18.6 m³/s in model simulations. Overall, the catchment’s hydro-climatic behavior is dominated by variability rather than long-term monotonic change. CHIRPS provides a valuable tool for hydrological monitoring in this data-scarce basin, though bias correction is needed for extreme events. These findings underscore the importance of adaptive measures, including drought-tolerant crops, flexible reservoir operations, and improved monitoring systems, to mitigate the impacts of climate variability on water resources.