Groundwater quality under land use/land cover changes: A temporal study from 2005 to 2015 in Xi'an, Northwest China

Urbanization and land use/land cover (LULC) patterns significantly affect groundwater quality. This study investigated groundwater quality and LULC conversion of Xi'an City in Guanzhong Basin over ten years, from 2005 to 2015. The relationship between groundwater quality and LULC patterns were also explored. Piper diagram, Gibbs diagram, and self-organizing map (SOM) were used to investigate the hydrogeochemistry and groundwater quality in the city. Remote sensing image data generated by Landsat 5 and Landsat 8 satellites in 2005, 2010, and 2015 were used to extract the LULC patterns of Xi'an City in those three years. These data were used to determine the LULC conversion between 2005 and 2010, and between 2010 and 2015. Entropy weighted water quality index (EWQI), curved streamline searchlight model (CS-SLM), and multiple linear regression analysis were used to relate groundwater quality to the LULC patterns of Xi'an City in the three years. The Piper diagram indicated that groundwater in Xi'an City was mainly characterized as HCO3-Na type and/or HCO3-Ca center dot Mg type. The Gibbs diagram indicated that the dominant evolution of hydrogeochemistry was through rock weathering and water-rock interactions. SOM classified the groundwater into eight clusters, and revealed different spatiotemporal patterns of water quality parameters. The LULC classification indicated that the urban land in Xi'an City has expanded by more than 160%, while forest and agricultural land areas have reduced by 52.54% and 83.08%, respectively, from 2005 to 2015. Indicated by the coefficient of multiple linear regression of EWQI and the percentages of LULC types in CS-SLM for the wells, urban land, agricultural land, and industrial land had negative effects on groundwater quality, while the forest positively impacted the groundwater quality in the same period. This study is meaningful and significant because it supports sustainable urban development and groundwater management in Xi'an City.