عنوان مقاله [English]
Water resources are limited in arid and semi-arid regions. Hirmand catchment is one of the arid and semi-arid regions of the country. The agricultural sector is the largest consumer of water in the Hirmand catchment. In recent years, water shortages in the Hirmand catchment have hampered water supply for agriculture, the environment and drinking water. Therefore, integrated water resources management in this area is important. In this research, the aim is to simulate and optimize water consumption in order to integrate water resources in the Hirmand catchment. For this purpose, a water evaluation and planning model (WEAP) was used to simulate the water resources system of Helmand catchment and a multi-objective linear programming technique was used to optimize water consumption. In the reference scenario, water demand in the Helmand catchment is 1400 million cubic meters per year, which increases over time due to population growth in the drinking sector. The agricultural sector is responsible for the highest amount of water consumption in the Hirmand catchment. 75.18% of water consumption in Hirmand catchment is related to agriculture, 19.44% is related to the environment and 38.5% is related to drinking. The highest water shortage is related to the agricultural sector. 35.21% of the total water demand in Hirmand catchment is not met. The agricultural and environmental sectors are facing water shortages. 50.12% of water demand in the environmental sector and 31.63% of water demand in the agricultural sector is not met. If the current situation continues for the next 20 years, the problem of fine dust in the region will be inevitable. After optimization, water consumption in the Hirmand catchment area will be reduced to 382.82 million cubic meters and 93.60 and 89.03% of water demand in agriculture and environment will be met. In the reference scenario, the amount of water shortage in agriculture and the environment in summer is 170.562 and 90.535 million cubic meters and the amount of water supply is 95.407 and 0.010 million cubic meters. After optimization, the amount of water shortage in summer in agriculture and the environment will reach 18.090 and 4.302 million cubic meters and the amount of water supply will increase to 151.940 and 86.059 million cubic meters. In the reference scenario, the net profit of farmers in the agricultural sectors of Sistan, Zahak and Miankangi is 6365.506, 6390.649 and 3499.895 billion rials, respectively. With the optimization of the agricultural pattern, the net profit of farmers in the agricultural sector of Sistan has increased by 139.46%, the agricultural sector of Zahak has increased by 10.66% and the agricultural sector of the middle class has increased by 52.50%. After optimizing onion, sesame, tomato and garden crops were removed from the cultivation pattern of the region. Wheat, barley, herbs, sorghum, legumes, alfalfa and cucumber were selected as the most optimal crops. The area under cultivation of medicinal plants due to lower water requirements and higher net profit than other crops had the highest percentage of increase in area under cultivation. Wheat is also one of the optimal products due to the existence of protectionist policies such as the guaranteed purchase policy by the government and the absence of price risk for this product. Sorghum crop is climatically compatible with the tropical region of Helmand catchment area and has a high yield per unit area and as a result, high profitability in the agricultural pattern of the region.