IMPACT OF LAND MANAGEMENT PRACTICES ON GROUNDWATER RECHARGE: CASE OF EDO-WATERSHED IN THE ETHIOPIAN RIFT VALLEY BASIN

Abstract

Proper water resource planning requires an understanding of the availability and use of ground water. But, there is lack of information in the Edo watershed on groundwater availability, rate of recharge, and there is limited information on the impact of land management on groundwater. In line with this, the objective of this study was to determine the impact of land management practices on groundwater recharge and soil water dynamics on conserved land and bare land at the Edo watershed in Wondogenet. In this study, the Hydrus- 1D model and water table fluctuation methods were used to estimate groundwater recharge. Hydrus -1D model is the Richards-based vadose zone hydrological model. The meteorological, and soil hydraulic data were used as input data to the Hydrus-1D model. Soil hydraulic parameters were estimated from easily measured soil physical properties using ROSETTA-derived prior information about soil hydraulic parameters. Water table data from twenty-five wells was used to estimate the recharge. The model performance was evaluated by comparing the observed and simulated soil water content values both on conserved land and bare land in the study area. The high value of 0.997 and a low value of ME (0.049) for calibration and a high value of 0.99 for Conserved land and 0.93 for bare land and low (RMSE of 0.23-0.28, MEB of 0.057-0.23) values during validation showed that there was a good agreement between the observed and simulated soil water content. The overall evaluation according to the common performance evaluation techniques revealed that the observed and simulated soil water content in conserved land was higher compared to those in bare land. From the Hydrus -1D, the long-term average annual groundwater recharge was 3,976,409.32 m3 or 297.8896mm, which is 26.92 % of average annual rainfall, and the water table fluctuation method 257mm, which is 23.23% of average annual rain fall. From the result, it can conclude the conserved land was better than bare land due to storing more water. The current observation showed that good land management practices were useful to sustain the water resources in the watershed.