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Optimal Conjunctive use of Groundwater and Surface Water in an Irrigation Network

IWRA World Water Congress 2008 Montpellier France
1. Water availability, use and management
Author(s): A. Montazar
M. Riyazi
Irrigation & Drainage Engineering Department, University College of Aboureyhan,University of Tehran, Iran; email of corresponding author : almontaz@ut.ac.ir

Keyword(s): Conjunctive use model, Cropping pattern, Groundwater, LINGO, Surface Water, water productivity

AbstractShortages of surface water supplies necessitate development of groundwater in many canal commands. Hence, The conjunctive management of surface water and groundwater can increase the efficiency, reliability, and cost-effectiveness of water use in the irrigation networks. Several simulation/optimization procedures have been developed to study conjunctive use problems. In the present paper, the LINGO 10.0, optimization package has been used to arrive at optimal allocation plan of surface water and groundwater for irrigation of multiple crops. The objective function of the model was the water productivity of irrigation network, as an indicator to contribute to analyse issues on water management. The proposed optimization model was applied for Gazvin Irrigation Network, a semi-arid region in Iran. This irrigation network covers an area of around 57,000 ha in NW Iran. The water needed for the area is supplied from Taleghan Dam (with a longitude of 50° 17´ E, latitude of 36° 27´ N and altitude of 970 m above the mean sea level) and 102 integrated wells. In order to investigate the conditions of the water resources in the study area, 30-year (1976-2006) statistics of the meteorological stations in the region were used and the volume of water available for irrigation from surface water resources over both wet and dry years was estimated. Potential use of the groundwater in the conjunctive use planning has been explored by running the model for the different scenarios of surface and groundwater use. The non-linear programming-based conjunctive use model was used to investigate the different integrated water use policy options. First of all, model was run for the existing cropping pattern and irrigation practices to understand the present scenario, then various scenarios were investigated for proposed cropping patterns with different alternatives of surface and groundwater utilization. The results indicated that it is possible to increase the amount of current groundwater withdrawal by as much as 50% by modifying current withdrawal schedules, modifying the number and configuration of wells in the supply-wells, or allowing increased surface water depletion of network. The findings explained that the water productivity of irrigation network may be improved 28% in drought condition using the optimal conjunctive of groundwater and surface water. The proposed model can be an effective tool for exploring the potential advantages of using regionalized surface water treatment and tradable groundwater permits in the pursuit of sustainable groundwater management strategies.
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