Long-Term Changes of Metrological, Hydrologic and Underground Water Resources of Dasht-e-Argan Basin and Their Impacts on Argan Internationally Important Wetland

Arjan wetland is one of the most internationally important wetlands of Iran.  This wetland has been dried in the last two decades, except for short periods in other dry seasons. The purpose of this research was to study the long-term changes in meteorological and hydrological conditions using the data of stations located in the wetland watershed and adjacent watersheds. To this end the rainfall, evaporation, temperature and groundwater aquifers status and runoff of the wetland basin were analyzed. The data showed a decreased trend of precipitation and severe underground water harvesting in the studied area. Comparison of the amount of water stored in the reservoir of Arjan wetland in the current situation (95.49 mm3) to what reported in the Atlas of Water Resources of Iran (109.40 mm3) shows a significant decrease in recent years. Comparison of the current estimated runoff (13.90 mm3) with one reported in the Atlas of Water Resources (15.64 mm) shows a decrease in this factor. Moreover, the results showed that the groundwater level had a decreasing trend and the last estimated years had the lowest levels which clearly shows the negative impacts of numerous wells have been dug in the studied area. In conclusion, the results of this study show that the drying of Arjan wetland is affected by both climatic and anthropogenic factors. But the impact of anthropogenic factors is much more serious and it is strongly recommended to reduce the water harvest from aquifer to rehabilitate the wetland.