Assessing Variability in Monthly Rainfall and Water Balance in Kayonza District, Eastern Rwanda

Abstract

The distribution and variability of rainfall are crucial factors in understanding climate change, especially for regions reliant on rain-fed agriculture. This study investigates the variability in monthly rainfall and water balance in Kayonza district from 1983 to 2021 by using the coefficient of variation. The results show that monthly rainfall varies between 0 mm and 25 mm in June-July-August, and 75 mm to 200 mm in the rainy months of March, April, October, and November, primarily concentrated in the southern, central, western, and eastern parts of the district. Water balance ranges from 0 mm to 70 mm, with higher water balance in the southwest during April and May. Rainfall exhibits higher variability (100-160%) in June and July, while lower variability (0-40%) is observed in March, April, October, and November. Water balance shows non-uniform variability, with the southwestern, southern, central, and eastern parts showing variability of 30-80%, while other months are ranging from 100 to 150%. On a pentad and dekadal time scale, rainfall and water balance are concentrated in pentad 12 to 31, pentad 51 to 72, decadal 6 to 16, and decadal 25 to 35, with less precipitation in other periods. Region one receives more rainfall compared to region two. These findings are crucial for developing mitigation strategies to combat the impacts of climate change on agriculture, emphasizing water conservation and integrating climate data into decision-making processes.