Spatial distribution and temporal trends of rainfall and erosivity in the Eastern Africa region

TLDR

Soil erosion by water is a major environmental concern in drought‑prone Eastern Africa. The study aims to evaluate the spatial distribution and temporal trends of rainfall and erosivity in the region from 1981 to 2016. The authors analyzed precipitation concentration, seasonality, and modified Fournier indices using a 5 × 5 km resolution multisource rainfall product (CHIRPS). The analysis revealed that mean annual rainfall is 810 mm with a latitudinal seasonality gradient, 55 % of the region experiences high to very high rainfall erosivity, the mean R‑factor is 3,246 ± 1,895 MJ mm ha⁻¹ h⁻¹ yr⁻¹ indicating a potentially high erosion risk, and both increasing and decreasing rainfall and erosivity trends were observed with high spatial variability, providing useful data for soil erosion prediction and policy development.

Abstract

Abstract Soil erosion by water is one of the main environmental concerns in the drought‐prone Eastern Africa region. Understanding factors such as rainfall and erosivity is therefore of utmost importance for soil erosion risk assessment and soil and water conservation planning. In this study, we evaluated the spatial distribution and temporal trends of rainfall and erosivity for the Eastern Africa region during the period 1981–2016. The precipitation concentration index, seasonality index, and modified Fournier index have been analysed using 5 × 5‐km resolution multisource rainfall product (Climate Hazards Group InfraRed Precipitation with Stations). The mean annual rainfall of the region was 810 mm ranging from less than 300 mm in the lowland areas to over 1,200 mm in the highlands being influenced by orography of the Eastern Africa region. The precipitation concentration index and seasonality index revealed a spatial pattern of rainfall seasonality dependent on latitude, with a more pronounced seasonality as we go far from the equator. The modified Fournier index showed high spatial variability with about 55% of the region subject to high to very high rainfall erosivity. The mean annual R‐factor in the study region was calculated at 3,246 ± 1,895 MJ mm ha −1 h −1 yr −1 , implying a potentially high water erosion risk in the region. Moreover, both increasing and decreasing trends of annual rainfall and erosivity were observed but spatial variability of these trends was high. This study offers useful information for better soil erosion prediction as well as can support policy development to achieve sustainable regional environmental planning and management of soil and water resources.