CHARACTERIZATION OF SURFACE AND GROUNDWATER INTERACTIONS AT HARAMAYA LAKE CATCHMENT, EASTERN ETHIOPIA

Abstract

The surface and groundwater interactionis important part in water cycle researches.Theinteractionof the surface and groundwater at Lake HaramayaCatchmentwas characterizedin this study. The majorhydrological processes involved in surface andgroundwater interactionwere analyzed using different approaches.The direct runoff of the catchment was estimated using SCS CN method. The actual evapotranspiration of the catchment was estimated using Turc, Langbein and Wundit empirical formula.The direct groundwater recharge of the watershedswas estimated using soil waterbalance technique. Groundwater modeling was undertaken using processing MODFLOW.The interaction between the surface and groundwater of the study area was computed using ArcGIS software.The annual runoff estimated for Haramaya and Finkle watersheds respectively were 114 mm and 139 mm.The actual evapotranspiration values of 628 mm and 621 mm were estimated for Haramaya and Finkle watersheds respectively.The averageddirect groundwater recharges of the study area for the years (1997-2015) were68 mm and 49 mm for Haramayaand Finkle Watersheds respectively.Calibration results evaluated using statistical lumped sum description of the average differences of residuals between simulated and measured heads mean error (ME), meanabsolute error (MAE) and root mean square error (RMSE) were calculated for the residuals and found to be 0.94 m, 3.40 m and 3.80 m respectively.From this study, it was found that all the streamsin the catchmentare losing streams.Studiesthosework on increasing the groundwater recharge of the catchment to increase contribution of groundwater to thesurface watertochange this situation are recommended.