Development of Surface and Groundwater Allocation Strategies Using the Conjunctive Use Model, A Case Study: Zayandehroud Watershed
Due to the water shortage crisis, the conjunctive use of surface water and groundwater resources can be an effective approach in water resources management. So that in many cases, the water demands of agricultural, industrial, domestic and environmental sectors can be supplied in different months of the year considering the volume of renewable water of the aquifer and the water table drops. The simulation of different management scenarios are widely used to achieve the optimal conjunctive use policies. In this study, the conjunctive use of surface water and groundwater resources in the Zayandehrood river basin and specifically Najafabad aquifer has been carried out. The characteristics of the surface water and groundwater resources, water demands and boundary conditions of the case study for model preparation are gathered. The Najafabad aquifer is modelled and then the impacts of conjunctive policies of surface water and groundwater are simulated utilizing the Groundwater Vistas 4.0 software for seven years period with monthly time scale. In order to assess the sustainability of current and future conditions of water allocation strategies, a watershed simulation model is developed using WEAP software. Then different scenarios for exploring the management strategies are defined in the region. The developed groundwater model is calibrated and then a dynamic link between WEAP and GWV models has been created through utilizing the package of the groundwater model. After creating WEAP-MODFLOW model, the certain active cells in the MODFLOW model with WEAP elements are linked. In each time step, the surface and groundwater allocation to the different demand nodes and the returned flow to the aquifer are determined based on the WEAP-MODFLOW model. Then different operating scenarios under different management strategies are generated and their effects on water supplying of domestic, industrial, agricultural and the environmental are examined. The water tables in the aquifers are also simulated using the developed simulation model. Eventually utilizing hierarchical analysis process, (AHP) through the EXPERT CHOICE software, the best management strategy is selected. Based on the result of this study, the scenario including modifying the consumption patterns, the limitation of water withdrawals from the aquifer, the inter-basin water transfer projects and changing priorities in water allocation can effectively improve the reliability of water supply and the aquifer restoration in the long-term use of water resources.
Key Words: Conjunctive Management, Water Allocation, Simulation Models, Watershed Planning, Management Policies.