Excessive extraction of aquifers to produce agricultural products is reduced the amount of water in groundwater sources, in the manner that this amount decreasing follows irreversible effects in various areas. In order to decreasing difficulties resulting from decrease in amount of aquifer deciding in considerable level is needed. This matter has made balancing of aquifers as one of the important factors in water resources management. In this study, in order to recovery of groundwater sources and implementing extraction reduction in country's aquifers, as one of the equilibrium projects, optimization the cultivation pattern with economical approach and investigation changes farmer's profit with exploitation reduction scenarios to 1%, 3% and 5% From two popular perspectives and analytical comparisons between them is done in 1395. For optimize the cropping pattern, two perspectives of changing the cropping pattern have been used by NLP method and reduction of cultivated subspecies, and using PMP optimization method. Results of using extraction reduction scenarios in Qazvin plain's aquifer, which has yearly deficiency to the value of 376 MCM showed that in the scenarios of groundwater extraction, the values of 21. 2, 63. 7 & 106. 6 MCM of extraction are reduced from the aquifer of the case study. Also, the results of the analysis of the two planning methods showed that the NLP optimization model, gaining more economical profits than the PMP model.

In recent decades most countries because of water crisis tend to manage water resources and water allocation well. Water, the crucial element, is the most important factor limiting of economic development and input in Iranian agriculture. This study estimates the economic value of water with applying POSITIVE MATHEMATICAL PROGRAMMING between farmers in Quchan. The data, used of simple random sampling method, in this study completed by questionnaires between 118 of the farmers in Quchan. Then farmers were divided in 2 groups (farmers with less than 5 acres and more than 5 acres) with using analysis of variance that each group of farmers affected by the reaction of the three scenarios (decrease 30%, 40% &70% water resources for farmers group 1 and decrease 10%, 25% & 75% water resources for farmers group 2 also increase 70%, 80% & 100% in water price for farmers group 1 and 75%, 80% &100% for farmers group 2) were examined. The results showed that the economic value of water under scenarios of decrease water for farmers group 1 respectively equal 1100, 1340 & 3120 Rials and for farmers group 2 respectively equal 10, 1260 and 4730 Rials. Also the cultivation of products such as wheat, barley, potatoes and tomatoes has been less change than the existing scenarios.

In recent decades, due to water crisis, most countries have been more interested in new policies for managing water demand instead of regulating the water supply. In dry and semi-dry areas of Iran such as Fars province, water scarcity is not only the important factor that impedes economic development but also special input in production. Drought in year 2007 could be considered as a risk of crisis in water supply. So, the purpose of this study is managing water demand through economizing surface water and groundwater resources which is of special importance in the region. It is self-evident that agricultural economy has a close relationship with water management. In this research the standard POSITIVE MATHEMATICAL PROGRAMMING (PMP) method is used to calibrate the agricultural sector model. A two-stage stratified random sampling through personal interviews of Bakan from Eghlid farmers has been applied, where abundant water resources and groundwater exist. By selecting a real sample of farms, model calculation for both areas is carried out. Two scenarios are identified. In the first scenario, by using PMP model for each group from water resources are calculated separately. They differ in terms of net revenue which is because of overly cost of construction and operation of wells between the two groups of surface water and groundwater. Results show that 10% decrease in water supply or doubling the prices will not change the optimal crop pattern in comparison to the base pattern. The results of model calculation shows that through running new irrigation methods (intensive irrigation) and also by effective pricing policies, investment can be encouraged in the water sector and in the area and therefore, through optimum management of water demand the water resources can be saved and any form of waste avoided.

During recent decades, MATHEMATICAL PROGRAMMING models have many applications in the field of agricultural policies analysis and simulation of these policies on the different parts of agricultural system. So in this study were examined the impacts of increasing wheat price during the four scenarios of 10, 20, 40 and 60 percent on cropping pattern in Zabol city using MATHEMATICAL PROGRAMMING. The results showed that mungbean was eliminated from cropping pattern in all price scenarios also by implement scenario of 60% increasing price, barley and melon were excluded from cropping pattern and there was more emphasis on cultivation of wheat. Therefore infrastructure must be applied in a way that PROGRAMMING isn’t controversial for farmers.

In this study, the aim is to identify the economic and welfare effects of forming the water market in the Varamin region. Changes in the area under aquaculture, gross profit in two situations (water market and lack of water market) during 2011-2016 were calculated and compared using GAMS software and POSITIVE MATHEMATICAL PROGRAMMING model. The results show that the establishment of the water market would have a POSITIVE and incremental effect on the gross profit of farmers in the region. Also, Cultivation of crops such as wheat, rice, barley, cucumber and potatoes, tomatoes and garlic has been more profitable and more crops can be planted. Based on the results, it is suggested that the government provide private-sector participation through investment and financial incentives.

Water scarcity is a growing global problem and increasing population pressures, living standards and the growing demand for environmental quality have evoked all the governments to represent better solutions about water resources management. In addition, there are growing political ties for reducing water use in agriculture that follow enough environmental benefits and increase the welfare of other water consumers. This further increases the economic analysis to check the behavior of farmers using MATHEMATICAL PROGRAMMING techniques and has been followed the application of POSITIVE MATHEMATICAL PROGRAMMING (PMP) especially. Despite. The method used in this study is one of the PMP methods that used for deficit irrigation technique that haven’t been observed in the reference period. This method applied in Fars province that faces water shortages and the reduction of groundwater levels to evaluate the price increase and quantity reduction of available irrigation water. Applied policies include increased 5, 10, 20 and 30 percent in water irrigation prices and reduced 10, 15, 25 and 30 percent in the amount of available irrigation water policies. The results showed that increased costs and reduced available irrigation water are effective in accepting deficit irrigation. Additionally, the impacts of quota policies are more than price increase policies.

Pricing policy is generally recommended by economists for better water allocation which is not so welcomed by officials due to economic, cultural and political concerns. This paper offers some alternative policies for improvement in water allocation using POSITIVE MATHEMATICAL PROGRAMMING in Sarakhs' plain agronomy subsector (Khorasan Razavi province). Main results indicate that tax (reduction in level of support) on input and output can be used as alternatives for water pricing, though, the effects of proposed policies on income, water demand and cropping pattern is different from farmer to farmer. Also for crops with high water requirement, tax on output brings more suitable results.

This paper develops POSITIVE MATHEMATICAL PROGRAMMING (PMP) model to determine the optimum cropping pattern and water demand function in six regions of lower part lands of Shirindarre Dam in north Khorasan Province of Iran and then estimates the expected pay for water in each region. The quantity of water supplied from such different water resources as dams, wells, and rivers in different scenarios of wet, normal, and dry years has been calculated. Then The price equilibrium as well as the type of participation of farmers in the water market have been assessed by crossing the water supply and demand functions. The buyer and seller of water, volume of exchanges and exchange value have been calculated as based on a comparison of the expected pay for water and the equilibrium price in the water market. In this study the impact of water pricing on farmers, income, labor demand, consumption of chemical fertilizers and pesticides and as well on the government revenue have been investigated too. The results of the study indicate that the economic value of water has been estimated by 416 and 571 Rials per cubic meter in normal and drought scenarios respectively. These models have been solved through GAMS package under2007-2008  agricultural data.

In this study, the reaction of farmers to possible changes in the price and supply of irrigation water aimed at encouraging water-use efficiency and their effects on the social and private benefits were analyzed by using POSITIVE MATHEMATICAL PROGRAMMING method and considering 12 scenarios.Scenarios considered are: increasing 20, 40, 60 and 100 percent in the price of water along with 10 and.20 percent reduction in the available water supply; 80 percent increase in the price of water and 50 percent decrease in the water supply (drought condition); 20 percent increase in the price of water and 10 percent decrease in water supply (in Mashhad plain); liberalization of sugarbeet and fertilizer markets along with 10 percent decrease in water supply at the farm level. The finding showed that, under conditions of markets failure (externality) and distorting polices, raising water price and decreasing water supply, increase social benefit at the expense of private benefit.Farmers react to increasing water price by changing their cropping patterns but, do not necessarily decrease their total water consumption. However, the amount of water applied to each crop may increase. Decrease or remained unchanged. Results also showed that, in the presence of market failure and distorting policies, drought may not affect social benefits significantly. Moreover, the effects of product and factor price policies on the cropping patterns were different. That is, decreasing product price results in greater change in cultivated are acompared to increasing input prices.Based on the finding of this study, it can be concluded that, careful identification of policy target seems to be important in policy decision.