Effect of Rainfall Indices on Ground Water Resource Consumption andCropping Patterns(Case study: Shabestar plain from Urmia lake Basin)

Groundwater resources are important production factors in agricultural production. The excessive extraction of groundwater resources and the unfair weather conditions have made the important challenges in water resources management. According to this, reconsideration in management of water resources seems necessary. Shabestar plain is one of the most important areas of agriculture in East-Azerbaijan province that confront with excessive extraction of groundwater and water resources crisis. Given that rainfall is the main factor in nutrition of groundwater resources so, in this study was tried to investigate the effect of rainfall indices on volume and consumption of groundwater and cropping patterns using the dynamic programming model in Shabestar plain in ten-year (from 2001 to 2016) horizon. The results showed that there is strong correlation between 48-Monthly Standardized Precipitation Index (SPI48) and Groundwater Resource Index (GRI) and height of aquifer. Seting water pumping height on SPI48 caused the balance of aquifer gets better. In the current state of extraction, the aquifer's negative balance is about 10.44 million cubic meters per year. With the optimal extraction, the aquifer's negative balance of 8.26 million cubic meters in normal conditions decreases. If optimal water extraction is done according to the weather conditions, In the drought and normal conditions, the negative balance would be about 9 and 6 million cubic meters, respectively. In wet year conditions, the aquifer's balance will be positive and about 10 million cubic meters will be added to the aquifer volume. According to the results, in drought conditions crops cultivation of wheat, barley and grape increased and crops cultivation of tomato and alfalfa decreased. Reduce water extraction and consumption by using water saving irrigation technologies and also applying appropriate prices for low-water crops are the basic strategies for restoration of groundwater table in the Shabestar region.