Assessment of landcover impacts on the groundwater quality using hydrogeochemical and geospatial techniques

Abstract

Abstract Groundwater quality is significantly impacted by urbanization and land use land cover (LULC) changes. The current study investigated the impact of LULC on groundwater quality in Quetta city, Baluchistan province, Pakistan. During the years 2015 and 2021, a total of 58 groundwater samples were collected from drinking wells for chemical analysis. The hydrogeochemistry of groundwater was investigated using Gibbs diagrams, Piper diagrams, and spatial distribution maps. The water quality trend was depicted using the Wilcox, USSL diagram, and Water Quality Index (WQI) from 2015 to 2021. The LULC analysis of Quetta was carried out on Google Earth Engine's cloud-computing platform using imagery from the Sentinel-2 satellite with low cloud cover (<10%). The LULC data was later used to calculate the rate of landcover conversion between both years 2015 and 2021 which help to identify the spatial distribution of groundwater and assess its vulnerability to pollution. The findings indicate an increase in the urban and agricultural classes while a decrease in the barren class. Moreover, according to the Piper diagram, groundwater in Quetta was primarily classified as CaMgCl type, CaCl type, and NaCl type. The Gibbs diagrams show water-rock interactions and rock weathering as the dominant evolution of hydrogeochemistry. The majority of the groundwater samples in both years were suitable for irrigation, according to the Wilcox diagram, USSL diagram, and other agricultural indices. The WQI demonstrated that the groundwater sources in the area are safe for human consumption; however, in the northern parts, WQI values are declining due to urbanization over six years.