LAND USE-LAND COVER CHANGE IMPACT ON THE GROUNDWATER RECHARGE FOR FERFURO WATERSHED IN SILTE ZONE, ETHIOPIA

Abstract

This study focuses on the assessment of the impact of change of LULC on groundwater recharge in Furfuro watershed, Silte zone, Ethiopia. In the study area, there is no potential surface water resource, so the investigation and utilization of groundwater resources are in the catchment very crucial. However, no systemic study has been conducted on the impact of change of LULC on groundwater recharge in the study area. This study aims to assess the impact of the LULC change on GWR in the Furfuro watershed in the period between 2000 and 2020. Remote sensing and GIS techniques integrated with the WetSpass model were used for studying the impact of change of LULC on groundwater recharge in the Furfuro watershed. The satellite images obtained for the years 2000 (TM), 2010 (TM), and 2020 (OLI) and hydro-meteorological data for years between 1988 and 2018 were used. LULC classification was made using supervised image classification. There are five classified LULCs in the study area, which are built-up areas, forests, farms, shrubs, and bare land. Maximum-likelihood classification algorithm analysis showed an overall accuracy of 91.6%, 90.1%, and 89.6% for 2000, 2010, and 2020 images, respectively. The Kappa coefficients associated with the classification resulted in 87.5% for 2000, 84.7% for 2010, and 82.5% for the 2020 LULC image data. The change detection analysis showed that Furfuro watershed catchment experienced an increase in agricultural and buildup areas by 37.3 km2 and 6.91 km2, respectively over the past two decades. On the other hand, forest, shrubs, and bare land were decreased by 20.3 km2, 9.73 km2, and 14.14 km2, respectively. WetSpass model estimated the average annual spatial water balance components for 20 years period and the results showed that the average annual actual evaporation was 387.5mm (35.42%), surface runoff was 574mm (51.9%), and GWR was 137 mm (12.7%). Model response the LULC changed for 2000 produced GWR was 149.84 mm, for 2010 analysis GWR was 141.46 mm and finally 2020 GWR was 138 mm from average rainfall 1085.1mm for thirty yraes. These results showed that there was a gradual decrease in GWR in two decades due to LULC changes. Generally, because of the change in LULC over the last 20 years, the GWR decreased by 11.84mm. This study shows the negative impact of change of LULC on GWR and hence implementing appropriate land use management strategies shall be helpful to conserve the groundwater resource by enhancing the recharge rate.