Application of a loose coupling model for assessing the impact of land-cover changes on groundwater recharge in the Jinan spring area, China

The Jinan spring area is one of the fastest developing and most water-stressed regions of China. Because of rapid urban expansion, groundwater recharge has been greatly influenced by land-use/cover change (LUCC). To gain an improved understanding of how the groundwater recharge affected by LUCC from 1960 to 2015, normal years, including 1985, 2000, and 2015, were selected using the Pearson-III distribution. Land-cover types of the normal years were classified using Thematic Mapper images. A loose coupling of an urban expansion model and a hydrological model was used to quantify the impact of LUCC on groundwater recharge. The results showed that land converted to built-up land was mainly mixed forest and arable land. The proportion of land-use types that remained unchanged was generally less than 50%, except for built-up land. In 2030, the area of built-up land will continue to increase, while the area of arable land and mixed forest will decrease correspondingly. The mean annual groundwater recharge was 88.32, 87.95, 73.31, and 76.17 mm for 1985, 2000, 2015, and 2030, respectively, which accounts for 14.01, 12.90, 12.20, and 11.98%, respectively, of the annual precipitation. In the water balance of the study area, only a small fraction (11.98–14.01%) of precipitation recharges the groundwater, and the remainder is lost by evapotranspiration (81.41–82.05%) and to a lesser extent by surface runoff (4.15–6.83%). The amount of groundwater recharge is mainly controlled by precipitation and potential evapotranspiration. Recharge is negatively correlated with the drought index. The ratio of groundwater recharge to precipitation decreased at a rate of − 0.06% from 1985 to 2015. The recharge/precipitation ratio is expected to decrease by a further 0.22% by 2030. The decrease in the ratio is primarily the result of an increase in built-up land areas, and a decrease in mixed forest and arable land areas.