Investigation of Fahlian aquifer subsidence and its effect on groundwater loss

Abstract

Land subsidence is one of the natural and geological hazards that can occur naturally or as a result of human activities such as long-term groundwater abstraction and traditional agriculture. In the last two decades, following climate change and successive droughts, as well as improper management of water resources, the uncontrolled abstraction of groundwater and the increase in population growth have caused land subsidence in Fars province, especially the Fahlian Basin in the northwest of the province. In general, the present study aimed to monitor and measure land subsidence using radar interferometry and also to analyze the relationship between groundwater level changes and land subsidence in the Fahlian Basin. DINSAR method was used to estimate the displacement of the ground surface and produce a map of the average displacement speed. The results of interferometric data show the continuous occurrence of subsidence in the agricultural lands of the region. The average rate of this deformation is about 4 cm per year, and in most parts, the amount of subsidence during the three consecutive years 2016, 2017, and 2018 is equal to 0.09, 0.11, and 0.12 cm, respectively. Also, the results of the study of groundwater level drop changes in 12 piezometric wells for the period 2009–2017 are −0.36 to −10. The overall correlation between groundwater level changes and subsidence levels was estimated at 75%, indicating the dependence of subsidence and groundwater decline in the region.