Investigating changes in climatic dry conditions across the water management zones in Uganda

Abstract

Prolonged insufficient precipitation associated with evapotranspiration affects society in various ways such as wilting of crops. Studies with comprehensive analyses of climatic droughts while considering hydro-climatic differences among the various Water Management Zones (WMZs) in Uganda are inadequate. This study addressed this, by extracting extreme climatic indices (ECI) from precipitation and potential evapotranspiration (PET), characterizing climatic drought across the WMZs and analyzing connection of variability in the indices to large-scale oceanatmosphere conditions from 1979 to 2013. Examples of the extracted ECIs included number of dry days (NDD), number of consecutive dry days, and sum of PET, above a defined threshold. The long term statistics of the extreme climatic conditions showed Kyoga and Victoria as the driest and wettest WMZs in Uganda. The extent and severity of drought were found to depend on the threshold for extracting the ECIs. Furthermore, the severity of the drought was found to be disproportionate across the country with the Kyoga and Victoria WMZs being the most and least severely affected by the impacts of climatic drought. Generally, all WMZs exhibited decreasing trends in the NDD over the study period, indicating that the country was becoming wetter recently. Across the country, the Indian Ocean Dipole (IOD) was negatively correlated with variability of a number of ECIs of both precipitation and PET. However, correlation between Quasi Biennial Oscillation (QBO) and variability of several ECIs was generally positive (p<0.05). Key words: Drought, Climatic Indices, Evapotranspiration, Variability, Trend