Planning for Sustainable Management of Groundwater Resources, Case Study: Nishapur plain in Iran
Dept. of Civ. Engr.UNESCO Chair in Water & Environ. Mngmt for Sustainable Cities,Sharif Univ.of Tech
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Sustainable management of groundwater resources is essential for sustainable agriculture in arid and semiarid regions. Groundwater should be managed to be effective, efficient and robust- balancing changes in demands and supplies over time and space and to ensure that there are no negative long-term irreversible or cumulative impacts on ecosystems. The two important considerations in defining sustainable yield are spatial and time scales. Sustainable yield should be defined on a scale small enough to address important local impacts, but large enough to recognize the ability of aquifer systems to adjust to pumping stress. Sustainable yield must also be defined over a specific time period. Pumping, recharge, and ecological response are all time dependent, changing over varying time scales of days, seasons, and years. So, in order to minimize the adverse impacts, sustainable yield should be defined according to the availability of water in different time scales. In Iran, due to its arid-semiarid climatic condition and limitations of dry farming, groundwater management has an essential role in agriculture as well as drinking water supply. Over the years, the agricultural expansion has resulted in over-exploitation of groundwater resources in almost the whole country. Groundwater depletion has caused many problems such as land subsidence, reduction in base flow of the rivers, destruction of wetlands, increasing the cost of pumping, and salt water intrusion in coastal areas. Studies show that over 90 percent of the groundwater basins in Iran are over-exploited and facing ever increasing depletion. The purpose of this paper is to optimize the spatial and temporal scales of Nishapur plain in Khorasan Province in north east of Iran, in order to maximize sustainable yield and minimize negative impacts of groundwater withdrawal. Uncontrolled withdrawal of groundwater resources threatening social integrity and security of the region evidently shows the importance and necessity of planning for sustainable groundwater use in the region. Planning for sustainable management of groundwater resources is a complex task due to its long-term nature faced with many uncertainties. Considering the conditions of the Nishapur plain, different management scenarios are analyzed using MODFLOW and the concept of “capture” to determine sustainable groundwater discharge as follow: changing crop pattern, increasing irrigation efficiency, and improving water productivity; changing the temporal distribution of water use; wastewater reuse; surface water resources development projects; and controlling GW pumping. Having determined the sustainable aquifer discharge in each scenario, Game Theory is used to determine the optimal groundwater resources allocation to different consumers. To consider the effect of uncertainty and participation of stakeholders in the sustainable management of groundwater resources, Bayesian Belief Network (BBN) is used. Hugin software is used for the development of BBN network structure based on the conceptual model of the study area. Available information and data and the results of the integrated model of water resources and uses provide the input data to the network. The main results of this study are the estimate of the regional groundwater sustainable yield as well as the required time to achieve groundwater sustainability in different scenarios.