Investigation of water allocation using integrated water resource management approaches in the Zayandehroud River basin, Iran

The Zayandehroud River is the largest river in the Gavkhouni basin, Iran. Water management in this basin is beset by poor water-allocation policies that do not adequately meet diverse demands (potable, agriculture, in-dustry, and environmental demands). The Gavkhouni basin suffers from water scarcity and unmet water de-mands; especially with respect to environmental requirements. Water allocation considering appropriate priorities for all demands would be a major improvement for environmental protection in the Gavhouni basin. The application of the environmental flow in Integrated Water Resource Management offers practical options for water management in the Gavkhouni basin. Environmental flow describes the quantity, timing, and quality of water flow required to sustain freshwater, estuarine ecosystems, the human livelihoods, and well-being. A water resources management model is developed in this study for the purpose of improved water management in the Gavkhouni basin. The model involves six stages. The first stage implements a survey of resources and water use. The Environmental flow is calculated in the second stage with the hydraulic method and the Hydrologic Engi-neering Center-River Analysis System. The third stage applies the calculated environmental flow to the Inte-grated Water Resource Management approach by means of the Water Evaluation and Planning model. The fourth stage creates seven possible management scenarios in the Water Evaluation and Planning model to be applied in the period ending in the year 2041. These scenarios are ranked in the fifth stage with a multi-criteria decision -making method. The sixth stage applies the best management scenario in the study region. This study's results indicate that the annual drinking water demand under current conditions would rise from 547.6 to 760.2 Mm3 by 2041. The annual industrial water demand is estimated to increase from 213.7 to 400.5 Mm3, and the agricul-tural water demand is projected to remain constant at 1789.1 Mm3 per yr. The annual drinking water, envi-ronmental, industrial, and agricultural unmet demands are estimated to increase from 68.1, 106.5, 73.4, and 470 to 130.1, 186.1, 141.4, and 480 Mm3, respectively. The considered scenarios are (i) change in water supply priority, (ii) change in the population growth trend, (iii) change in return flow and water loss management utilization, (iv) change in the amount of water transferred to the Gavkhouni basin, (v) change of demand management (consumption per capita reduction), (vi) change of agricultural conditions, and (vii) change of industrial conditions. The change in water supply priority and the change in the volume of water transferred to the Gavkhouni basin scenarios are found to be of the highest priority. The best management alternative is chosen with four types of ranking (i.e., water allocation priorities) in which the ranking (i.e., drinking, Industrial, agricultural, environmental unmet water) and fourth ranking (i.e., environmental, drinking, industrial, agri-cultural Unmet water) are recommended as the best approach.