simulation water market and analysis of the effects irrigation water sharing policy on cropping patterns under conditions of water shortage

in the recent decades, due to water shortage problems, most countries have adopted their new policies from water supply management to water demand management . the main objective of the present study is a simulation of water market in order to determine the role of market in the balance between water supply and water demand and to analysis impacts of irrigation water sharing policies on the cropping patterns under conditions of water shortage in the shahrood river basin. for this purpose, positive mathematical programming (pmp) model and regional agricultural production functions were used. after the model design, irrigation water sharing policies in consistent with the legal deviations for each of the three different cases were simulated. finally, deficit irrigations under the three scenarios 10, 20 and 30 percent were conducted. the data was adjusted based on the reference year of 2011. a part of the data was collectedby completing the questionnaires and interviews in person with farmers from the three regions western alamut roudbar, rajai dasht and eastern alamut roudbar.the other part of data was collected by visiting the relevant offices in the city of qazvin. to solve the proposed model, the software gams version of 23/9 was used. the results showed that application of irrigation water sharing policy is a suitable approach for the allocation of water resources of the shahrood river basin. furthermore, the results showed that establishming the water market and trading between the regions increases the economic benefits for farmers. the applied irrigation deficit from 10 to 30 percent increased the total area of irrigated crops from 9 to 37 percents.