Seasonal variability of total streamflow, runoff, baseflow, and baseflow index in the fetam catchment, Upper Blue Nile Basin, Ethiopia

Abstract

Groundwater is often a primary source of freshwater in many parts of the world. Fetam River Catchment is among the major river catchments in Ethiopia’s Upper Blue Nile River Basin, where groundwater is a primary source of freshwater. Seasonal rainfall fluctuations, climate, and anthropogenic factors strongly influence the quantity and quality of surface water. Therefore, estimating groundwater recharge is essential for understanding aquifer dynamics and provides a critical basis for sustainable groundwater management. The main aim of the investigation is to estimate the amount of water recharged to the aquifer using the soil moisture balance and Baseflow separation methods in the Fetam River Catchment, and to determine water management thresholds for sustainable development. Fifteen years of River flow data and ten years of daily meteorological data have been used for Baseflow separation and daily soil moisture balance, respectively. Daily soil moisture data analysis yielded a recharge rate of 253.1 ± 78 mm/year, and time-series baseflow data yielded a recharge rate of 187.5 ± 13.23 mm/year. Therefore, the average recharge rate of the catchment based on the two recharge estimation techniques is 220 ± 45.6 mm/year, a sufficient renewable resource. Despite the effects of numerous factors, Baseflow resulted in an underestimation, and the soil moisture balance is overestimated in the investigated area compared to the average of the two techniques. Therefore, the recharge value for river catchments under similar geographical and meteorological circumstances is better estimated by the average of all methods than by any individual technique.