One of the most important factors in the agricultural sector is the supply of water. There are numerous factors affecting the supply of water in the agricultural sector. One of these factors is urban development. After the agricultural and industrial revolution, urban revolution is one of the most important issues in the economic development of countries. Urban development has two implications for agricultural water use; this both increases the demand for agricultural crops and the consumption of water in the household sector, which both lead to a reduction in available water in the agricultural sector. Therefore, determination of the impact of urbanization on water consumption in agriculture is necessary. In this study, we have examined the extended positive mathematical programming method on the agricultural sector of Qazvin Province. The results of the study showed that 1% increase in urbanization would reduce water consumption in agriculture by 0.639 mm3 compared to the base year. Also, household water consumption will reach 92.92-761.9 mm3 in base year. On the other hand, the cultivated area and the production of some irrigated crops (wheat, barley, rapeseed, sunflower, other oilseeds, alfalfa) will decrease to 86.36 hectare and 346.6 tons. In the indirect effect of increasing urbanization, per each percentage urbanization, the household water consumption will decrease by 2.19 mm3, and after a 20-year horizon, the total capacity of the Taleghan Dam will be allocated to Tehran's household water,. So that, 288 mm3 of agricultural water will be reduced, and it will reduce the cultivated area for 28,250 (ha). Also, farmers' gross profits will be 10.5 percent lower than the base year which is a threat for Qazvin plain farming. Solutions were proposed to reduce the negative effects of the urban development phenomenon, including the use of modern irrigation systems in the agricultural sector will significantly increase irrigation efficiency. So that only 1% increase in irrigation efficiency can completely neutralize the direct and indirect negative impacts of urbanization on a 12-year mid-term horizon.
Keywords: Crop production; Extended positive mathematical programming; Household water demand; Indirect and direct urbanization; Qazvin plain.