Temporal and Spatial Analysis of the Groundwater Quality Variations in Faradonbeh Plain and Evaluation of Its Usability for Agricultural Uses During 1991-2019

Nowadays, due to the limited groundwater resources and increasing population, and growth of agriculture and industries, optimum operation of groundwater needs more attention. In this research, temporal and spatial changes in the quality of groundwater resources in Faradonbeh Plain located in Chaharmahal and Bakhtiari province have been investigated.

For this purpose, the time series of qualitative variables collected from 7 sampling stations (including 6 wells and one spring) in the Faradonbeh plain during a 29-year period (1991-2019) was used. The trend of changes in groundwater quality variables of this plain was investigated using the modified Mann-Kendall test (after completely removing the autocorrelation effect). Also, for each time series, the trend line slope was calculated using the Sen slope estimator. In order to draw the delineation maps of qualitative variables, Kriging method was used in the Arc GIS software. Finally, the usability of groundwater for agricultural use in Faradonbeh plain was investigated using USSL diagram.

Comparison of delineation maps of qualitative variables showed that the groundwater quality of this plain has decreased in recent years, especially in the central parts of the plain. Also, the results of he USSL diagram indicate a decrease in the quality of groundwater for agricultural uses.

Due to the expansion of agriculture lands in this plain, the overexploitation of groundwater resources and indiscriminate of fertilizers and chemical pesticides can pose a serious threat to the water resources in the region in terms of quantity and quality. Also, the use of industrial and municipal effluents for irrigation in the long-term can have adverse effects on the life cycle of this region due to undesirable changes in soil and the possibility of leakage of these pollutants into groundwater, especially in the central part of this plain.