An assessment of meteorological drought occurrence and severity in Uganda.

Abstract

In the tropics, precipitation in the form of rainfall varies seasonally resulting into droughts and floods as extreme weather events that are causing great economic impact especially on agriculture and water resources. Although meteorological drought is of major concern in Uganda, its magnitude of severity has not been assessed. This study aimed at i) identifying Uganda’s climatological zones prone to meteorological drought and ii) determining meteorological drought duration and occurrence and iii) magnitude of drought severity in the identified prone zones. Rainfall deciles method was used to analyse monthly rainfall data for 40 years (1943-1982) in 16 climatological homogenous zones (A1, A2, B, CE, CW, D, E, F, G, H, I, J, K, L, ME, MW). Seven of the 16 zones were identified as drought prone (CE, CW, E, G, H, ME, MW), whose annual and monthly rainfall ranges are 274–1157 mm and 10–94 mm; respectively. Some identified zones experience drought in January-February and June-August while others do so in November-Mars. The average drought event interval in any drought prone zone is 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 is 12½ years. Severe drought (M-2s) was dominant in zone H with 22.5% occurrences during the December-February season whose drought rainfall range was ≤ 10 mm. Most drought prone zones experience moderate type of drought (M-s) with highest occurrences (62.5%) in zone MW during the September-November season whose drought rainfall range was > 114 < 150 mm. Zone CW was the only zone that recorded drought with M-3s (‘extreme’ drought) with 2.5% occurrences. The study recommends that the results may be adopted in disaster management especially prioritising areas that have recorded highest occurrences in the different types of drought and the monthly drought rainfall range of all the drought prone zones (10–94 mm) may be adopted for drought monitoring on a seasonal basis in Uganda.