Steady-State Numerical Groundwater flow Modeling Using Processing MODFLOW in Case of Upper Mille River Catchment Upper Awash Basin North-Eastern Ethiopia
| dc.contributor.advisor | Nedaw, Dessie (PhD) | |
| dc.contributor.author | Godie, Amanuel | |
| dc.date.accessioned | 2021-11-23T06:35:42Z | |
| dc.date.accessioned | 2023-11-09T14:13:02Z | |
| dc.date.available | 2021-11-23T06:35:42Z | |
| dc.date.available | 2023-11-09T14:13:02Z | |
| dc.date.issued | 2021-09-15 | |
| dc.description.abstract | Different approaches have been used to investigate the hydrogeology of a complex fractured volcanic and unconsolidated Quaternary sediment aquifer system in the Upper Mille catchment (part of the lower Awash basin) located at the western escarpment of Afar rift. The water balance components of the watershed have been estimated using Water Balance (WB) and SWAT modeling techniques. The mean annual precipitation, actual evapotranspiration, surface runoff, and groundwater recharge of the watershed has been quantified as 1132mm, 775mm, 251mm, and 105mm respectively by the WB method whereas, using the SWAT model these components are estimated as 1083mm, 558mm, 335mm, and 150mm respectively with an interflow of 39mm. The groundwater system and the spatial variability of the different aquifers have been studied using conventional hydrogeological investigation, and numerical groundwater flow modeling techniques. The watershed has been classified into different hydrogeologic units based on the productivity of aquifer units using the data obtained from lithologic logs of deep boreholes, pumping test results, stratigraphic settings, and topographic position of each unit. Based on this, the lithologic units were classified into three hydrogeologic units; high productive intergranular aquifer, medium productive fractured aquifer, and low productive aquifer having different conductivity, transmissivity, and discharge amount as observed from drilled boreholes. Schematic hydrogeological cross-sections, TDS and EC distribution maps, and groundwater head distribution contour maps were produced using lithologic logs of drilled deep boreholes, field measured inventory water points, and water level measurement respectively. Based on converging evidence from geological, hydrogeological, and topographic settings a conceptual model that approximates the groundwater system of the Upper Mille watershed was developed. The conceptual model was converted into a numerical groundwater flow model by applying a steady-state groundwater flow model governing equation using Processing MODFLOW packages. The model was simulated and model calibration carried out by manual trial and error adjustment of the input parameters until the values of the observed and simulated head results were within the acceptable error. Head distribution and water budgets of the watershed was quantified. The calibrated model simulates a mean annual groundwater recharge of 89.1mm/year. The total inflow and outflow of the system is almost equal (3.73× 107m3/day). The results of the sensitivity analysis indicates that the model is highly sensitive for a change in hydraulic conductivity and recharge rate. Two types of scenario analysis were done. The first scenario was by increasing the amount of groundwater extraction by 50, 100, and 200% from the current pumping rate. The simulation results in an average decline of water level by 12.2, 19.1, and 23m respectively. The second scenario was analyzed firstly by decreasing the recharge by 50% while keeping the current rate of pumping and then simultaneously decreasing the current recharge by 50% and increasing the groundwater abstraction by 100%. In these cases, the model shows an average decline in simulated hydraulic head by 7m and 17.4m from the current water level. | en_US |
| dc.identifier.uri | http://10.90.10.223:4000/handle/123456789/28845 | |
| dc.language.iso | en | en_US |
| dc.publisher | Addis Ababa University | en_US |
| dc.subject | Water Balance | en_US |
| dc.subject | Recharge | en_US |
| dc.subject | Hydrogeological Unit | en_US |
| dc.subject | Conceptual Model | en_US |
| dc.subject | Numerical Model | en_US |
| dc.subject | Calibration | en_US |
| dc.subject | Scenario Analysis | en_US |
| dc.subject | Sensitivity Analysis | en_US |
| dc.title | Steady-State Numerical Groundwater flow Modeling Using Processing MODFLOW in Case of Upper Mille River Catchment Upper Awash Basin North-Eastern Ethiopia | en_US |
| dc.type | Thesis | en_US |