Numerical Groundwater Flow Modeling Of the Gerado River Catchment
| dc.contributor.advisor | Mebruk, Mohammed (PhD) | |
| dc.contributor.author | Kidest, Ayalew | |
| dc.date.accessioned | 2019-01-17T08:54:56Z | |
| dc.date.accessioned | 2023-11-11T08:32:17Z | |
| dc.date.available | 2019-01-17T08:54:56Z | |
| dc.date.available | 2023-11-11T08:32:17Z | |
| dc.date.issued | 2018-12 | |
| dc.description.abstract | In this study, a one dimensional groundwater flow model under steady state condition was constructed as a tool to understand the aquifer system of Gerado River catchment using numerical groundwater flow modeling. The study was ambitious in the sense that the modeling was conducted with limited data, particularly for the highland tertiary volcanic part of the basin due to absence of wells in the highland. The groundwater storage is in the alluvium and in the fractured volcanics. The aquifers in the rocks and alluvial sediments are assumed to be hydraulically linked or interconnected. The groundwater flow system in the two aquifers of the basin was modeled using MODFLOW (McDonald and Harbaugh, 1988). The model was run for steady-state conditions in for unconfined aquifer. The grid cell size of the model was taken 250 x 250m. Model area and the layer top elevation were delineated by the DEM processing and use of topographic maps. The hydraulic conductivity values were found from pumping test data analysis and literature review for the alluvial sediment aquifer and the volcanic aquifer respectively. Recharge for the area was estimated using the water balance approach and gave 148.95mm/year or 13% of the rainfall. The model Calibration was using trial and error approach results were evaluated using statistical lumped sum description of the average differences of residuals between simulated and measured heads (mean error, mean absolute error, root mean square error & R2) were calculated for the residuals and found to be 1.5m,5.29m,6m and 0.88m respectively. The average recharge obtained by the model is about 151mm/year which closer to the manually calculated value of 148.95mm/year. The total groundwater in Gerado catchment is 39.3 MM 3 3 /year. This volume of water compared with the total abstraction in the basin (about 2.6 MM /year) is good storage and can sustain well abstraction at the existing rate or more than the existing in the future. Simulated heads were sensitive to recharge and hydraulic conductivity in similar fashion. As observed from the values, the model was most sensitive to both decrease in the recharge and hydraulic conductivity values, mainly beyond 50 percent and less sensitive to both recharge and hydraulic conductivity increasing of the value. The responses of the aquifer to different scenarios were investigated with increased withdrawals and decreased recharges. The effects of increased in groundwater withdrawal rate by 50% cause decline in groundwater level with a maximum of the water level by 1.08 m and a minimum of 0.19m,decreas groundwater discharge through general head boundary and Base flow to river. The second scenario is effect of decrease in groundwater recharge by 25 % due to less than normal precipitation cause maximum decline of the water level by 2 of the water level by 23.09m and a minimum of 2.98m , decrease of groundwater discharge through the general head boundary & Base flow. | en_US |
| dc.identifier.uri | http://etd.aau.edu.et/handle/12345678/15852 | |
| dc.language.iso | en_US | en_US |
| dc.publisher | Addis Ababa University | en_US |
| dc.subject | Groundwater Flow | en_US |
| dc.subject | Gerado River Catchment | en_US |
| dc.title | Numerical Groundwater Flow Modeling Of the Gerado River Catchment | en_US |
| dc.type | Thesis | en_US |