The effect of water resources on spatial and temporal change of soil salinity in Izdkhast playa, Fars Province, Iran.

Abstract

In the south of Fars Province in Iran, there are several closed basins where the salinity of water and soil resources is one of the main problems. Therefore, to manage the water and soil resources of these basins, identifying the source of salinity and its expansion in playa is necessary. Thus, the Izad-Khast pit in the south of Fars Province of Iran was selected as one of these basins for research. To achieve the goal, 16 soil samples were randomly taken from the basin, and their EC was determined. Landsat 8 image was selected according to sampling day, and ten salinity indices were extracted from it. Then, the best index was determined by the relationship between salinity indices and ground EC using linear regression. Using the determined index and linear equation derived from linear regression and Landsat 7 and 8 images, salinity maps were obtained in three periods 2010, 2015, and 2020. Then, using maps of the three mentioned intervals and the CA-Markov method, soil salinity prediction maps were extracted for 2025 and 2030. Based on the research results, salinity index S2 = (Blue - R)/(Blue + R) provided the best results. Salinity maps derived from this index show that the highest level is related to the area with no salinity or low salinity, and high degrees of salinity are concentrated in some parts of the hills and in some areas of the plain, respectively, which determines the origin of salts. The results also showed that the kappa coefficient of CA-Markov is 0.7282, which shows the high ability of the model to predict soil salinity, in which the distance factor from gypsum and salt minerals is the most critical predictor factor. According to the forecasts, from 2020 to 2025, about 1 km2 and then from 2025 to 2030, about 1.6 km2 will be added to the saline lands.