عنوان مقاله [English]
Constructed Earth dams in the watersheds of Ramhormoz and Shadegan have two destructive roles: First, they create new sources of dust production in the dry years, the second; they will activate the sources of dust production of the south and southern parts of Ahwaz by preventing the flow of seasonal flows, in wet years. In this study, regarding to the distribution of hydrological network, the study areas in which earth dams were constructed on the seasonal streams leading to the southern and southeast of the dust resources of Ahvaz, were identified and selected. In order to investigate the effects of Earth dams on the water flow of the rivers, long-term statistic data of the hydrometric and rain gauge stations which are located in Ramhormoz watershed were used. For this purpose, linear trend, slope of variation, significant and change points of climatic and hydrologic parameters of precipitation and flow rate were investigated using Mann- Kendall graphical method. Due to the lack of access to the information in the Shadegan study area, the location of the Earth Dams on the seasonal streams of the northeast of the dust resources was identified through Google Earth and the year of their construction was achieved through the study of Landsat satellite imagery in January. Due to the large number and small sized Earth Dams, variation in their surface water levels were estimated using visual interpretation of 5, 7, and 8 Landsat satellite imagery, and analyzed using Arc GIS software In the study area, based on the drought index, the years of drought and wet were identified and the results showed that the linear trend of time series of the flow rate and rainfall has been decreased both, however, the slope of decreasing trend in the time series of the flow rate has been more and significant. In addition, the results of the study showed that some of the earth dams, especially in Ramhormoz area, were destructed and filled with the sediment and, in other sections, the variation in the level of water collected behind them follow the drought and wet conditions so that the area of the water zone in January 2016 as a wet year, in 21 Earth Dams in the northeast of the dust resources was approximately 21 hectares and, in January 2017, as a dry year, was approximately 21 hectares, which can be a good potential for controlling the dust in this resources. The relationship between the frequency of dust events with the internal origin and the cumulative frequency of constructed Earth Dam showed that the increasing the number of Earth Dams in these two areas could be one of the factors affecting the activation of dust resources in southwest of Ahwaz.