Investigation of Effects of Land Use Land Cover Changes on Quantity and Quality of Groundwater in Qazvin Plain

Groundwater is a very important natural freshwater resource for drinking and irrigation purposes. In the present study, the aim is to investigate the effect of Land Use/Land Cover (LULC) changes on the quantity and quality of groundwater in Qazvin Plain from 2005 to 2020, through RS-GIS using LULC maps from Landsat 5 TM and 8 OLI images, Groundwater Resource Index (GRI) and Groundwater Quality Index (GQI). For this purpose, the data from groundwater level and quality parameters including K+, Na+, Mg2+, Ca2+, SO42-, Cl-, TDS and EC were employed. The results indicated that in the central and eastern parts of the plain, the area of agricultural land and the number of exploitation wells were more than other parts. The plain was mostly covered with rangeland and agricultural lands. The area of agricultural land had the most changes over the time. GRI results illustrated more droughts in the eastern parts of the plain over time, and GQI results showed that groundwater quality has significantly decreased in the eastern parts in 2020. The non-vegetated lands had increased in the eastern parts of the plain, which can be due to the increase in agricultural lands, in which the excessive use of groundwater resources had reduced its level and thus decreased its quality. Generally, increasing agricultural lands and high density of exploitation wells in these lands had the greatest impact on the quantity and quality of groundwater in the Qazvin plain. So, the use of groundwater resources should be properly managed to prevent the reduction of its quantity and quality.