Assessment of Land Subsidence due to Groundwater Exploitation by Using Differential Radar Interferometry Technique, Case Study: Qazvin Province

Excessive harvesting of groundwater has caused a decrease in the water table, and as a consequence increasing in the phenomenon of the land-subsidence. Although, field inspection is the most accurate way to measure land subsidence and water table variation, it is less attractive due to the costs and being time consuming. Instead, the low cost and accurate remote sensing techniques are implemented for the large scale land subsidence measurement. The purpose of this study is to quantify the land subsidence in Qazvin province by using synthetic aperture radar interferometry and evaluating the effect of the groundwater depletion and soil profile on this phenomenon. For a long time land-subsidence evaluation, the combination of the outcomes of Envisat, Alos palsar-1, and Sentinel-1 satellite data between 2003 to 2017 are employed. Water table variation of Qazvin’s aquifer was studied using 180 data points of the pizometric wells. Annually averaged land-subsidence in this years was obtained as 39.9 mm/year for aquifer zone and this value was 33 mm/year for Qazvin province. According to the land-subsidence zone in Qazvin province it was revealed that most of the land-subsidence occur in the region of the aquifer whose fine-grained layer thickness would be larger than other areas. The maximum of Land subsidence was obtained at the northern parts of Buin-Zahra and near the Takestan borderline. This area has the highest cultivated area and groundwater depletion. The results of this study showed a strong correlation between the groundwater water table variations and land subsidence values in Qazvin province.