Soil moisture spatio-temporal variability under treated and untreated catchment conditions in a fragile tropical highland environment: implication for water security

This paper reports soil moisture spatio-temporal variability as influenced by catchment management in the Blue Nile Highlands, Ethiopia. The study was motivated by the need to support the mainstreaming of water security into improved catchment management initiatives. The specific objectives are to (1) determine major environmental factors influencing soil moisture spatio-temporal variability, (2) assess soil moisture spatio-temporal variability under traditional and improved catchment management conditions, and (3) understand the implication of improving catchment management for improving water security. Soil moisture and weather data were monitored intensively between 2017 and 2018 in a pair of agricultural catchments receiving traditional and improved management. A range of factors was found to contribute to soil moisture spatio-temporal variability in the study catchments, including rainfall, air temperature, relative humidity, antecedent soil moisture content, elevation, measurement depth, groundwater table, and catchment management. Soil moisture daily variation was strongly influenced by air temperature, rainfall, relative humidity, and antecedent soil moisture content, whereas soil moisture seasonal fluctuation was controlled by rainfall seasonal pattern. Of all experimental sites, the highest elevation (2032 m) presented the driest soil moisture regime (0.104 m3 m−3) while the lowest elevation (1965 m) displayed the moistest soil moisture regime (0.369 m3 m−3). The results demonstrated that improved catchment management has modified soil moisture response in the treated catchment, reducing soil moisture spatial heterogeneity and temporal variability. We conclude that improved catchment management can play a crucial role for improving agricultural water security in rainfed systems by improving soil moisture availability and storage.