ESTIMATION AND PREDICTION OF THE INTERACTION OF SURFACE WATER AND GROUNDWATER: A CASE STUDY OF AWASH SEBAT KILO AREA
Creators: name: YOSEF TAMIRAT SHIFERAW
Publisher: name: National Academic Digital Repository of Ethiopia
Year: 2019
Subjects: Groundwater-surface water interactions, QSWAT, SWAT-MODFLOW

description: Interaction of the surface and groundwater is one of the main processes of water exchange in the planet and<br> estimation of these groundwater-surface water interactions is critical to modeling surface and ground waters. This<br> thesis presents these interactions using hydrogeological survey, hydrochemistry study, QSWAT models and the<br> coupled SWAT-MODFLOW models. QSWAT is applied here to understand the water balance components of the<br> study. The same is also done using the SWAT-MODFLOW models. Calibration and validation of the QSWAT model<br> was conducted after carrying out the sensitivity analysis. The groundwater and management parameters are more<br> sensitive as compared with others. The SWAT model was calibrated with daily stream flow data ranging from 1999<br> to 2008 and validated with the same stream flow data ranging from 2009 to 2013. Two years were used for the<br> model warm up or initialization. The model goodness-of-fit was evaluated using the Coefficient of determination and<br> the Nash-Sutcliffe Coefficient on a daily basis both for calibration and validation periods and resulted 0.84 and<br> 0.79 for the calibration period and 0.87 and 0.871 for the validation period respectively. From the QSWAT model<br> the annual precipitation of the whole of the study catchments was averaged about 856mm over the entire basin, of<br> which 201.4mm (23.52%) goes to the surface runoff, 459.07mm(53.62%) to the evapotranspiration, 77.9mm (9,1%)<br> to be recharged to the aquifer. The SWAT-MODFLOW model also shows a good match with the QSWAT model<br> results. The outputs of the SWAT-MODFLOW model are also ET= 54.32% of precipitation, surface runoff=24.71%<br> of precipitation) and recharge=8.8% of precipitation. The result is therefore in good correlation with that<br> calculated by QSWAT. The goodness of fit comparison using the coefficient of determination and the Nash-Sutcliffe<br> Coefficient shows 0.8544 and 0.769 respectively. From the conducted hydrogeological survey, the conceptual model<br> of the water system of the study area was developed. The two main regional groundwater flow directions of the<br> basin are directed along the predominant anomaly axes (regional tectonic structures) of the area. These two<br> regional flow directions are separated by a NNE-SSW trending horst structures which also act as a surface and<br> ground water divide. The boundaries of the study area are bordered by ground and surface water divides along the<br> western, eastern and northeastern directions. The most likely recharge types and areas of the study area are: the<br> recharge from the perennial Awash River for a length of about 130kms, the groundwater inflow from the volcanic<br> aquifer of the Southern part of the plain for a length of about 74kms, recharge from rainfall within the basin and the<br> recharge from run off along the valleys of other perennial and intermittent rivers of the area. The groundwater<br> leaves the system in the extreme north of the plain along the NNE direction. Both chloride and sulphate salinity<br> increases along the ground water flow path of the study area. Therefore, from this we can conclude that the ground<br> water evolves along the flow direction. This is in view of enrichment of the salinity due to dissolution of minerals.<br> The study would have been better if the grid size of the SWAT-MODFLOW model was reduced and I recommend<br> doing the model at grid size of 1000m by 1000m or lowering. The hydrogeological and hydrochemical analyses<br> were done using scarce data at the western part of the study area and I recommend conducting test well drilling and<br> physic-chemical analyses of these drilled wells to enrich the document in the future.<br>