عنوان مقاله [English]
نویسندگان [English]چکیده [English]
Mesopotamian Marshes are among the largest wetland areas in the world with an area of over 9,000 square kilometers. This area composed of three main wetlands that are named Central, Hawizeh and Hammar wetlands. Hawizeh Wetland (Hoor-Alazim Wetland in some publications) has an area of 3,000 square kilometers, which lies between 47^° 30^' and 48^°longitude, and 31^°and 31^° 50^' latitude. It is located between the end of the east delta branches of the Tigris and the end of the Karkheh River in the Iran-Iraq border. About one-third of this wetland is located in Iran which is known as Hoor-Alazim. In recent decades, by implementing multiple dam constructions and irrigation networks projects in Hawizeh Wetland basin and also wrong policies of the Ba'ath regime of Iraq in diversion of Tigris River, the Hawizeh Wetland is not in appropriate status. This wetland, once was controlling dust has become a source of dust which causes negative impacts on society, economic, environment and human health in affected areas, such as many southern provinces of Iran. The effect of dust storm is not limited to the inside of the region. In other words, it has cross-border impacts and so the cooperation between countries to deal with this problem and prevent its occurrence is necessary. The purpose of this research is evaluating and modeling of water resources in the downstream of Karkheh Dam (in Iran) and Tigris River (in Iraq and Turkey), using WEAP (Water Evaluation and Planning System) software. In this regard, various scenarios, such as development scenarios (A3, A2 and B2) and natural (no project) scenarios (A1, B1), were applied for the current and future (2042) conditions to assess the supply of environmental water demand for Hawizeh Wetland. To increase accuracy and reduce error of simulation, this model was calibrated and validated at two points. The first point was chosen on hydrometric station on Tigris and the second point was selected on four hydrometric stations (K3, K4, K5 and K6) which are located on tributaries of Karkheh River, near the Hawizeh Wetland. To simulate the Tigris River Basin, discharge of hydrometric station T1 in Faysh Khabur area (where the Tigris enters Iraq) with the volume of water use from the Tigris River and its tributaries in Turkey was considered as the headwater. Then the various water uses including agriculture, industry and drinking as well as runoff and streams were added to Tigris River model and the results were calibrated and validated in a hydrometric station. In order to estimate the amount of errors in calibration and validation of the simulation model, the Mean absolute relative error (MARE) was used.
The calibration error in the first and second sections in the downstream of Karkheh Dam and the hydrometric station T8 in Tigris River basin were obtained as 0.055, 0.077 and 0.033, respectively. The results showed that the best way to restore Hawizeh Wetland is A1 and B1 scenarios, in which the environmental water demand is unsupplied with the index of 2.5% and 9%, respectively, in Karkheh and Tigris basins. Moreover, the worst state are A3 and B2 scenarios in which environmental water demand was unsupplied with indices of 45% and 33%, respectively, in the basins of Karkheh and Tigris. The value of indices in scenarios A3 and B2 demonstrate that if the current trend in water resources development in Tigris and Karkheh rivers be continued and a comprehensive water management plan is not performed for the basins, the Hawizeh Wetland will not be existed anymore in the future and it will become a source of dust storm.
As a conclusion, the results also showed that not only in development scenarios A3 and B2, the wetlands environmental demand is not provided but also it happened in natural scenarios A1 and B1 with the indices of 2.5% and 9%, respectively. It is proved that if the effects of existing and planned development projects of irrigation, drainage and dams be ignored, there are still reasons such as unsuitable cropping patterns and use of traditional irrigation methods which are the obstacles for the supplying environmental water demand. Furthermore, with existing and planned development projects of irrigation, drainage and dams, Hawizeh Wetland undoubtedly will not occur any longer in the future and it will be converted to a source of dust storm.