Assessment of March-May Rainfall Characteristics and Effect on the Stream Flow Of River Kafu in Masindi District Catchment, Uganda
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Kafu River catchment is vulnerable to changing climate because it relies heavily on rainfall. The study main objective was to assess the patterns in MAM rainfall and effects on the stream flow of River Kafu in Masindi district in Uganda. The data used in this study was observed daily rainfall for the period 1980-2013 of Masindi meteorological station as recorded by the rain gauge. This data was obtained from Uganda National Meteorological Authority (UNMA). Gridded daily rainfall data (1998-2013) from Tropical Rainfall Measurement Mission (TRMM) was also used. Another set of data was daily stream flow from 1980-2013 obtained from Directorate of Water Resources Management (DWRM), Entebbe from a gauging station at Kafu river in Masindi. The daily rainfall spatial and temporal maps showed that the major rainfall patterns are generally oriented northeast to southwest for March, southwest to northeast for April and north to south for May, with general maxima and strong rainfall gradients located along the western, northeastern and southern parts of the catchment. The three months of the study of observed rainfall and stream flow showed different variations in the 30-day moving average for MAM rainfall and stream flow but the difference is slightly significant. April has coefficient of variation (85.3%) and contributes 40.2 % of daily mean MAM rainfall (10.5 mm), followed by May (72.7%) and March (33.6 %) while variation results in stream flow indicates that May has coefficient of variation (100%), followed by April (87.7%) and March with (87.0%). Results from 30-day moving average time series graphs indicated a general positive increasing trend in MAM rainfall patterns and stream flow for the whole period of study. Mann-Kendall results indicated an upward trend for stream flow and a downward trend for rainfall while scatter plot indicated a moderate relationship between rainfall and stream flow. Regression analysis indicated a weak negative linear relationship between MAM rainfall patterns and stream flow which is statistically significant and hence, a rejection of the null hypothesis. Therefore,there is a significant relationship between daily MAM rainfall and stream flow of River Kafu in Masindi district catchment and these results will be used to carry out water resource management plans to prevent the effects that might rise from the high and low flows of River Kafu.