Application of Integrated Hydro-economic Optimization Model for Water Resources Management of Qarehsou River Basin to Wetland Protection and Food Security

In recent years, climate change and global warming, by reducing rainfall and higher temperature, have increased the frequency and severity of drought and water scarcity in various parts of the world, including Iran. The study of the annual discharge of rivers located in Qarahsu basin (Golestan province) showed that this basin has also faced drought in recent years and since most of the water required of Miankaleh wetland is supplied from Qarahsu River, so Water abstraction for agricultural, urban and industrial uses will have a major impact on the ecosystem of Miankaleh wetland. Given that agriculture is the main economic activity in the Golestan province and also it is the largest consumer of water and food security providers in the region Therefore, reducing irrigation water consumption can provide the extra water needed to protect the wetland. In order to sustainable supply water required of Miankaleh wetland in Gorgan Gulf, and preventing to dry the wetland, and using area's capacity in food security, attending to water resources management is very important in Qarehsou river Basin and Gorgan Gulf (Miankaleh wetland).

In this paper, a hydro-economic river basin model was used to water optimal allocation of Qarehsou River among water users in the basin (including irrigation activities, urban, industrial, and fishery uses, and environment) and protecting the Miankaleh wetland ecosystem (Gorgan Gulf). The empirical river basin model includes three reduce forms of hydrological components, regional optimization components, and environmental components and can make the integrated linkage between hydrologic, economic, institutional, and environmental components. This model also simulates demand nodes' behavior under different drought scenarios. The linkage between the three model components allows a rigorous evaluation of the quantitative impacts of drought on water availability in the river basin under study, the effects on the users’ behaviors, and the private and social-economic benefits and costs of water use. The hydrological model of the river basin is based on the principles of water mass balance, which determine the volume of water availability in the different river reaches. This water available can be used for economic activities after taking into account the environmental restrictions for economic activities. In the economic component, the economic benefits of water demand are maximized by using water demand functions subject to technical and resource constraints. In the environmental component, we maximize the benefits that environmental characteristics provide for society and compare them with the benefits of other applications.

The results showed, in the current condition, the allocation and consumption of water have not been optimal between nodes in the Qarehsou river basin. In the normal water supply scenario, also total water sources decreased to protect Miankaleh wetland in suitable condition, but the area under cultivation of the most crops increases, which increases water resources consumption in this sector, and finally, the net benefits of the agriculture sector has grown positively. Also, by allocating 18 million cubic meters of water to the wetland, because of optimal water allocation, urban water consumption, and annual gross benefit increase, too. In drought conditions, because of water shortage due to climate change and reduction headwater and surface flows to preserve the wetland, water consumption reduced by all nodes, especially irrigation node. Agricultures can prevent from reducing excessive of their income by changing in cultivation pattern, deficit planting crops with less water, etc. Under droughtconditions and water scarcity, although the amount of water available is reduced to all applicant nodes compared to baseline conditions, but it improves the economic benefits of stakeholders, especially the environment sector.Increasing groundwater extraction and decreasing surface water (due to drought and wetland water supply from headwater flow), although Qarehsou river basin has faced water scarcity problem, due to the optimal distribution of water between water demand nodes based on the economic-hydrological model used by changing the cultivation pattern and the use of drought-tolerant crops, the amount of water entering the Miankaleh wetland has increased in normal and drought scenarios and as a result has increased the gross environmental benefits of Qarehsou basin. Therefore, it is recommended to protect the Miankaleh wetland and increase its ecological function, reduce the water allocated value to irrigation sector, and to increase the farmers economy efficiency, optimal cultivation pattern, and applying deficit irrigation strategies promote by agricultural jihad experts in province, and in drought conditions is used suitable strategies for drought to improve water resources management.