عنوان مقاله [English]
Introduction: Among the critically forbidden plains of Tehran province, Varamin plain is more critical. The agricultural sector in this plain consumes more than 80 percent of the underground water resources. In the Varamin plain, most farmers tend to use traditional irrigation methods such as flood and leaky irrigation to irrigate their lands. According to economists, the reason for the low efficiency of irrigation and the loss of water resources in this sector, which has led to the current situation of the Varamin plain, is the low price of water compared to the other inputs. Therefore, it is essential to review the current method of water pricing and determine the reasonable water price in this plain. So, this study was conducted to answer these questions: What is the economic value of water in the Varanin plain? How can a change in water price affect the crop pattern and the farmers' profit? What are the responses of farmers to changing the price of this input? How much can a rise in water prices save the water input? Answering these questions can be a step towards modifying the pattern of water consumption in the Varamin plain. Therefore, this study aimed at calculating the economic value of the water and then, analyzing the impact of an increase in water price on farmers' reactions and the crop pattern in the Varamin plain.
Materials and Methods: The economic value of water was estimated through two methods: calculating the residual value by subtracting the cost of all inputs except water from the income for each product and evaluating the shadow price of water using Positive Mathematical Programming (PMP). Then, the impacts of water price changes on the crop pattern, water consumption, and farmers' profits were estimated using PMP model. The water demand function and water elasticity also were estimated by a stepwise increase of 5 percent in the water price in the third stage of the PMP model. The required data was collected by completing 120 questionnaires using the stratified sampling method and proportional allocation from the farmers of three cities in the Varamin plain including Varamin, Pishva and Pakdasht in the cropping year of 2019-2020. The data were collected for six crops (wheat, barley, corn, alfalfa, cucumber, and tomato), including the quantity and price of production and the quantity and price of inputs (land, seed, fertilizers, pesticide, water, labor, and machinery) in the concerned cities.
Conclusions: The weighted average of each cubic meter of water using the residual value as well as the shadow price methods were equal to 35769.8 and 23917.6 IRI rials, respectively. This result shows a big difference between the economic value and the price paid by farmers, which is between seven to ten-folds. The results of estimating the demand function of water showed that the water demand elasticity was equal to zero up to the price of 27386.1 IRI rials. At higher prices, the farmers responded to the increase in water price, and the elasticity of water demand was equal to -2.15 on average. Based on the results, the shadow price of water obtained from PMP model (23917.6 IRI rials) does not affect the crop pattern and the water consumption, although it reduces farmers' profit by 48.66 percent. The economic price of water obtained using residual value method (23917.6 IRI rials) causes a decrease of 36.84 percent in the cultivated area, a 25.24 percent reduction in the water consumption, and a 74.59 percent reduction in the profit. Most of the change in the cultivated area was related to barley. Although, this crop consumes less water per hectare than other crops, the share of water cost per kilogram of barley is higher than the other products. After barley, the cultivated area of wheat, alfalfa, corn, cucumber, and tomato would respectively decrease for the same reason.
Results and Discussion: The results showed that applying the policy of increasing the price of water up to its economic value led to a decrease in farmers' profits and might reduce their motivation in production. In addition, applying this policy suddenly can lead to adverse reactions such as resistance and avoidance of paying this water price, social tensions, and public discontent. Therefore, gradually adjusting and increasing water prices for a long time was suggested. By adopting this policy, gradually, agricultural water consumption would decrease, and the cropping pattern would shift toward water-saving crops.