Meteorological drought occurrence and severity in Uganda

Precipitation, a very important weather parameter is often variable, resulting into droughts and floods as extreme weather events in Uganda. These are causing great economic impact especially on agriculture and water resources. Meteorological drought is a creeping hazard; it develops slowly and has a prolonged existence leading to the development of other drought types such as agricultural and hydrological drought. Despite meteorological drought being a major concern in Uganda, drought occurrence and severity is not been well documented. This study determined the occurrence of meteorological drought and assessed the magnitude of its severity in Uganda. The rainfall deciles method was used to analyse monthly rainfall data for 40 years (1943-1982) in the 16 climatological homogenous zones of Uganda. Seven of the 16 climatological zones were identified as drought prone (CE, CW, E, G, H, ME, MW). The annual and monthly rainfall ranges for identification of drought were 274–1157 mm and 10–94 mm respectively. The occurrence of drought oscillated within 10-15 drought events per 5-years over the assessed period while the average drought event interval in any drought prone zone was 1-6 years with an average dominancy in occurrence of 1-year. The event interval for drought to occur concurrently in all the drought prone zones in a year was 12½ years. Severe drought was dominant in zone H with 22.5% occurrences during the December-February season whose drought rainfall range was ≤ 10 mm. The drought prone zones experience a moderate type of drought with highest occurrences (62.5%) in zone MW during the September-November season with a drought rainfall range of > 114 < 150 mm. Zone CW was the only zone that recorded drought with ‘extreme’ drought with 2.5% occurrences. It is therefore imperative that drought management is approached from a prioritization perspective focusing on the hotspot locations experiencing high occurrence of different drought types. Drought managers and decision makers consider using annual and monthly drought rainfall ranges of all the drought prone climatological zones for drought monitoring on an annual and seasonal basis in Uganda.