Using soil erosion as an indicator for integrated water resources management: a case study of Ruiru drinking water reservoir, Kenya

Abstract

Functions and services provided by soils play an important role for numerous sustainable development goals involving mainly food supply and environmental health. In many regions of the Earth, water erosion is a major threat to soil functions and is mostly related to land-use change or poor agricultural management. Selecting proper soil management practices requires site-specific indicators such as water erosion, which follow a spatio-temporal variation. The aim of this study was to develop monthly soil erosion risk maps for the data-scarce catchment of Ruiru drinking water reservoir located in Kenya. Therefore, the Revised Universal Soil Loss Equation complemented with the cubist–kriging interpolation method was applied. The erodibility map created with digital soil mapping methods (R2 = 0.63) revealed that 46% of the soils in the catchment have medium to high erodibility. The monthly erosion rates showed two distinct potential peaks of soil loss over the course of the year, which are consistent with the bimodal rainy season experienced in central Kenya. A higher soil loss of 2.24 t/ha was estimated for long rains (March–May) as compared to 1.68 t/ha for short rains (October–December). Bare land and cropland are the major contributors to soil loss. Furthermore, spatial maps reveal that areas around the indigenous forest on the western and southern parts of the catchment have the highest erosion risk. These detected erosion risks give the potential to develop efficient and timely soil management strategies, thus allowing continued multi-functional use of land within the soil–food–water nexus.

Spatio-temporal modeling of lake’s ecosystem and dynamism in response to changing environment. A case study of L. Olbolossat in Kenya

“…Vegetation acts as surface runoff regulator which ensures that there is less runoff hence increasing in ltration and reducing soil erosion. These ensures that the runoff carries less silt load to the lake basin which increases the lake extent (Kamamia et al, 2022). But in contrast to this, the vegetation has been cleared and therefore there is a risk of the basin shrinking due to the silt carried to the rivers by surface runoff water (Plate 1).…”

Modelling crop production, river low flow, and sediment load trade-offs under agroforestry land-use scenarios in Nyangores catchment, Kenya

“…The largest impact of land-use change on catchment hydrology can be linked to deforestation. This change, driven by exponential population growth, intensified food and industrial production (Foley et al, 2005;Kamamia et al, 2022), has resulted in alterations in the river flow regime such as high peaks, reduced base flows, and silt deposition in water bodies and reservoirs (Bajocco et al, 2012;Borrelli et al, 2017;Kamamia et al, 2021). Furthermore, climate change has accelerated land degradation by intensifying extreme events such as droughts and floods whose ramifications have been especially felt in the developing countries (Borrelli et al, 2017).…”