Climate change impacts on precipitation extremes: potential and perceived implications for water resources management across Uganda

Abstract

Water resources are increasingly being affected quantitively by climate change impacts. This requires carefully planned adaptation measures. This study investigated climate change impacts on precipitation extremes indices, including the annual maximum series (AMS), Severe dry spell (MDS1). Climate Forecast System Reanalysis (CFSR) was used to characterise historical precipitation conditions. Output from the eight General Circulation Models (GCMs) was used to project climate change signals for the 2050s, 2070s, and 2090s. Bias of a GCM output over the historical period (1985-2014) was assessed in terms of the ratio of observed to the model’s output. The best result, indicating no bias, would be indicated by a ratio of 1. The perception of water users in the various Water Management Zones (WMZs) across Uganda was assessed. The AMS over the study period 1985-2014 ranged from about 45 mm/day to nearly 55 mm/day in Victoria and Upper Nile WMZs, respectively. The biases in reproducing observed AMS ranged from 0.06 (for MPI-ESM1-Ham in Kyoga WMZ) to 0.82 (for INM-CM5 in Victoria WMZ). The best performance was exhibited by ACCESS-CM2 being the sole exception, demonstrating nearly accurate AMS estimation in the Victoria WMZ with a bias of about 1.01. Future projections of AMS under SSP245, SSP370, and SSP585 scenarios predict decreasing AMS in the Upper Nile WMZ (up to about 16% decline by 2090s) but increasing in Victoria WMZ up to about 60%. A survey (using questionnaire administered to water users of sample size n = 737) revealed that about 60% of respondents observed reduced precipitation, with approximately 48.1% expecting further declines. Nearly half (49.7%) cited extreme disruptions in rainfall timing, leading to agricultural losses and income reduction. Findings from both GCMs and the assessment of perceptions of water users show the need for carefully planned climate change adaptation in the various WMZs.