پیش‌بینی اثر متقابل آبخوان- رودخانه در دشت دوسلق، استان خوزستان با استفاده از مدل MODFLOW

Integrated management of groundwater and surface water is an important issue, particularly in the basins that considerable interactions exist between surface and groundwater resources. Reliable estimates of the total catchment water balance and hydrological water level fluctuations requires the aquifer- river assessment.
Modeling is one of the indirect ways of studying the groundwater resources which has gained a lot of attention nowadays, due to its high efficiency and low cost compared to other methods.
In this study, a quantitative groundwater model has been made for Dosalagh plain with an area of 816 km2, which is located on the south of Andimeshk and west of Karkheh River.
The main objectives of groundwater modeling in Dosalagh plain is to get a quantitative understanding of groundwater interaction between the river and aquifer. The results of this study provide valuable information for the optimized management of aquifer and further detailed studies of aquifer such as qualitative simulation.
The Groundwater Modeling System (GMS) Import and pre- and post-processing tools (collectively herein called as the GMS Import tool) have been developed to facilitate the linkage of GMS groundwater models with existing models associated with the Framework for Risk Analysis in Multimedia Environmental Systems (FRAMES). The GMS Import tool allows a GMS user to easily execute a reactive Multi-Species Transport in Three-Dimensional (RT3D) module or Modular Three-Dimensional multi-Species Transport Model (MT3DMS) module in FRAMES from a GMS-based RT3D-calibrated or MT3DMS- calibrated groundwater simulation. Through pre- and post-processing tools, the “created” RT3D or MT3DMS module in FRAMES has the capability to access and modify inputs to RT3D or MT3DMS without having the GMS user interface and without invalidating the GMS calibration. Although the GMS Import tool allows the FRAMES user access to modify input information to RT3D or MT3DMS and consume output from RT3D or MT3DMS. The basic design is applicable to all models housed within GMS or other such systems.
The program's modular design enables the user to select modules in custom combinations, allowing the user to choose only those groundwater modeling capabilities that are required. Additional GMS modules can be purchased and added at any time. The software will dynamically link to these subsequent modules at run time - automatically adding additional modeling capability to the software. The purpose of this study is to construct a simulation model capable of simulating the groundwater system as well as the groundwater- surface water interactions.
A three-dimensional, finite-difference ground-water flow model (MODFLOW) that incorporates a new stream-aquifer interaction package did the flow simulation. First, a steady state simulation was performed to represent mean annual conditions. Then groundwater flow in the plain was calibrated under unsteady state condition from October 2008 to September 2009 and verified during October 2009 to September 2010. After reaching the conclusion that the model could simulate the groundwater flow in the plain, it was used to evaluate various scenarios for management, including increasing withdrawal, decreasing recharge and increasing recharge and aquifer- river interactions in all scenarios were assessed by zone budget package of MODFLOW.
The results of the groundwater model showed that in the third scenario (increasing recharge) water flows from the river to the zone 1 of the Dosalagh aquifer during the wet season. Since in the wet season, the water exchanges decreases from +8227 to +7150 cubic meters per day due to increase of aquifer hydraulic gradient. In the zone number 2 water flows from aquifer to the river from -6800 to -7530 cubic meters per day and in the zone 3, the exchange of water from the aquifer to the river increases from -497.5 to -547.081 cubic meters per day.
After the calibration and verification, the model simulated the natural condition of aquifer properly and was used as a management tool for evaluating different management plans.The results of the groundwater model showed that in the third scenario (increasing recharge) water flows from the river to the zone 1 of the Dosalagh aquifer during the wet season. Since in the wet season, the water exchanges decreases from +8227 to +7150 cubic meters per day due to increase of aquifer hydraulic gradient. In the zone number 2 water flows from aquifer to the river from -6800 to -7530 cubic meters per day and in the zone 3, the exchange of water from the aquifer to the river increases from -497.5 to -547.081 cubic meters per day.
After the calibration and verification, the model simulated the natural condition of aquifer properly and was used as a management tool for evaluating different management plans.