Estimation of Aquifer Hydraulic Properties to Model Groundwater in Selected Area in Diyala Governorate

Abstract

ABSTRACT The groundwater resources are an important component of arid and semi-arid countries such as Iraq. The pumping tests are conducted in the shallow unconfined aquifer (Quaternary sediments) within Baquba Local Government Area, Diyala Provence, Iraq to estimate of the aquifer properties as there is limited information on aquifer parameters. Drawdown/Recovery data are recorded in seventeen single pumping wells and two monitoring wells at distances of 4 and 20 m from the pumping well in Abu-Khamis and Al- Othmania places, respectively. Type-curve matching of the drawdown/ recovery data are analyzed using Cooper-Jacob's Straight-line and Theis recovery methods. The ranges of the drilling wells depth are 15m to 38.4m. The aquifer saturated thickness ranges from 8 to 26 m. The outcomes of the pumping test data analysis show that the transmissivity values ranged between 124 to 541 m2/day with an average value of 245.3m2/day. The hydraulic conductivity ranged from 7.5 to 25.6 m/day with an average value of 14.5 m/day. The specific yield ranges from 0.05 to 0.28 with an average value of 0.12. The specific capacity of the wells ranged from 85 to 407 m2/day with an average value of 216 m2/day. The transmissivity values are analyzed according to Krasny Classification System (KCS) for identifying the transmissivity variations as well as the supply potential of the groundwater within the study area. The transmissivity classification results show that the II study area classifies as a high groundwater supply potential with slightly heterogeneous aquifer soil. The numerical model is adopted by transferred the conceptual model into GMS 10.0.5-MODFLOW2000 which is constructed to solve the groundwater flow equation with a finite differences technique. Two types of boundary conditions are applied (Neumann and Dirichlet conditions). The Neumann boundary condition is applied around the study area and the Dirichlet boundary condition represented the Diyala River. The model is calibrated by adjusted two parameters namely hydraulic conductivity and recharge rate. The best agreements between computed and observed head have been obtained. The sensitivity analysis results show that the hydraulic conductivity and recharge rate are a more sensitive parameter. After model calibrates, six different scenarios are investigated to study the impact of the discharge rate on the groundwater state. In these scenarios, the applying discharge rates are (current state, increasing about 25%, 50%, 75% and 100% above the current rate). Finally, proposed agricultural land with drilling new wells. The stress period that applied in transient state extended from (2018-2027) with ten-time steps. The unsteady state model simulation results for these scenarios show that the computed annual maximum drawdown values for the next ten years, according to the five scenarios, were equal to 11.43, 11.94, 12.25, 13.63, and 14.05 m respectively, while the annual maximum drawdown value was recorded in the proposed scenario (current rate with the rates of the new wells) equal to 11.87 m. The outcomes of this study have revealed that the Baquba shallow unconfined aquifer can production effectiveness amount of water for the people in this area, as well as, increase in discharge rates indicate III the possibility of drilling new wells within the study area without any mining of aquifer. Additionally, the model results reflect that the maximum values of the drawdown for the two regions of (Kanan and Buhriz) are very large, and according to this reason the management program is very important for dealing and manage the groundwater extraction in these regions.