نوع مقاله : علمی -پژوهشی
گروه جغرافیای طبیعی، دانشکده جغرافیا، دانشگاه تهران، تهران، ایران
عنوان مقاله [English]
Salt Lake basin of Iran contain about 30% of the total population and 5.6% of the total area of the country. The average annual reduction of groundwater level across this basin is -0.98 m. Due to this issue, Iran Water Resources Management Company has banned the exploitation of seven plains located around the Salt Lake. Therefore, by applying proper management and implementing exploitation management policies, groundwater level declination should be stopped. The artificial recharge approach can be used as an alternative to prevent further reduction of groundwater level. It is necessary to characterize the geological, geomorphological, soil and hydrological characteristics of the groundwater aquifer to select potential areas for recharge. The best places to implement artificial recharge plans are coarse-grained soils, early sandy alluvial soils, rocky soils, karst areas, sandy bedding and seasonal river cone deforestation. Studies have used a number of data-layers to identify potential areas for artificial recharge. The considered factors in each study were selected and evaluated according to the purpose as well as the hydrogeomorphological characteristics of the study area. In these studies, the runoff depth layer as one of the most important features has been rarely used in selecting susceptible areas for artificial recharge. Sharif-Abad plain is of great importance due to intense agriculture activities. Almost 99.9% of the total surface and groundwater consumption in this area (~1411.86 million cubic meters per year) is consumed by agricultural sector which has triggered significant declination of groundwater level.
Materials and methods
In this study, 10 data-layers including geology, geomorphology, soil texture, slope, land use, drainage density, ridge density, runoff depth, groundwater level after monsoon and distance from pumping wells are among the factors that define the suitable sites for recharge. Generation of these data-layers were performed in the ArcGIS 10.3 software environment with a 300 m resolution. The rating of each data-layer is conducted in the range of 1 to 4 according to its influence in suitable sites for recharge (1 for the lowest influence and 4 for the highest). The final map of the best sites for artificial recharge across the aquifer area were obtained by overlapping ten rated layers. Spatial cross-correlation between the values attributed the final map and values of the EC in the groundwater.
The final map obtained from the linear weighted combination of ten data-layers was divided into 4 categories including very suitable, suitable, inappropriate and completely inappropriate areas for artificial recharge. The very suitable areas for artificial recharge were characterized with the coarse-grained alluvial deposits, areas with deep groundwater level, low electrical conductivity, intense pumping well density, transverse passage of a fault line and low surface slope. A significant negative correlation equal to -0.635 is obtained between the EC layer and the final overlapped map.
In this study, suitable sites for groundwater artificial recharge in Sharif-Abad plain were obtained using the most substantial factors including geology, geomorphology, soil texture, land use/land cover, slope, runoff depth, lineament density, drainage density, depth of groundwater after monsoon, and the distance from the pumping wells. The results of this study showed that 11.16% and 30% of aquifer area are completely suitable and suitable lands for artificial recharge, respectively. The correlation of the overlaid final map with the corresponding values of the groundwater electrical conductivity equaled -0.635. Due to the hydrogeomorphological characteristics of the study area, an integrated surface and subsurface recharge (feeding pool and well methods) in the vicinity of fault line is recommended to implement the groundwater recharge project. The results of this research and the data-layers used to identify suitable sites for artificial recharge can also be used for other aquifers around the Salt Lake that have similar hydrogeomorphological-climatic conditions such as Sharif-Abad plain.