Groundwater is an extremely precious natural resource. It plays a key role in the hydrologic cycle, ecological and geological environment as well as economic and social development [1
]. As an important part of water resources, groundwater is preferred to be used for water supply than surface water due to its characteristics of wide distribution, strong storage capacity, good water quality and easy development [3
]. Precipitation infiltration is the main natural recharge source of groundwater. In recent years, the development of urbanization in Beijing, China, has greatly changed the underlying surface conditions. The land hardening and vadose thickening brought about by this change make the recharge amount of groundwater obtained from precipitation infiltration decrease continuously. However, in order to meet the economic development as well as the production and living needs, the exploitation of groundwater is still increasing year by year. To ensure the sustainable development of the city, it is urgent to evaluate the land use change on precipitation infiltration coefficient, runoff and groundwater in this case.
In the application of groundwater modeling, the precipitation infiltration recharge is determined according to the total precipitation and the precipitation infiltration recharge coefficient (
) in a certain area [5
]. The coefficient mainly depends on the lithology, structure and thickness of the vadose zone as well as the land surface slope [7
]. The natural amplitude of phreatic water level, lysimeter observation, isotope analysis, equilibrium method, chloride tracer and numerical simulation are usually used to calculate α [10
]. With the rapid economic and social development in recent years, a variety of human activities (such as the acceleration of urbanization process) have contributed to significant changes in land use and land cover, which directly affect the underlying surface of the basin [15
], and then changes the rainfall infiltration process.
Recently, researches about the influences of the land use change are abundant, including climate change [16
], hydrology and solute budgets [17
], streamflow [18
], and soil chemical attributes [19
]. By analyzing the characteristics of climate change (including spatial distribution and temporal trend of precipitation and temperature) and land use/cover change in Yunnan Province, China during 1961–2011, Shi and Chen [16
] concluded that the close relationships of the built-up land with the annual temperature and precipitation changes might be attributed to the developments of urbanization. Based on the lithology of unsaturated zone and the depth to groundwater table in different periods, Meng et al. [6
] discussed the temporal and spatial evolution characteristics of precipitation infiltration recharge in the North China Plain in recent 50 years. The study showed that with the increase of water table depth, the precipitation infiltration recharge coefficient increased and reached the peak value at a particular depth (the optimal depth of different lithology is 3 to 6 m). Cherubin et al. [19
] conducted the investigation on the effects of land use change on Brazilian tropical soil chemical attributes, indicating that long-term land use change from natural ecosystems to extensive pasture decreases available P, S, Ca, Mg and B contents, and land use change from pasture to sugarcane will lead to increase of nutrients levels and reduction of soil acidity. However, in the area where the groundwater recharge is dominated by the rainfall infiltration, the investigations on the impact of land use change on rainfall infiltration recharge remain limited. Therefore, it is important to study the variation of rainfall infiltration coefficient under the condition of underlying surface change.
The Soil and Water Assessment Tool (SWAT) model can comprehensively consider soil, land use, vegetation, land surface slope, meteorology, reservoir and runoff information to simulate different hydrological cycle processes. Jin et al. [20
] improved SWAT model to solve the problem that SWAT could not reflect the land use change during the simulation period. The improved SWAT model can use land use data year by year, and the simulation effect is better than SWAT Model in the Heihe River basin in China where land use and cover change greatly. SWAT model uses land use data in the modeling process, which will affect hydrological processes such as evapotranspiration and groundwater recharge [20
]. SWAT model has certain advantages in the calculation of groundwater recharge resources under the condition of underlying surface change. Based on the SWAT hydrological model, Mohamed et al. [21
] simulated the responses of streamflow and baseflow to climate and land use change in the Upper West Branch DuPage River basin in Illinois and the Walzem River Basin in Texas, respectively. The modeling results show that changes in streamflow and baseflow in the latter watershed seem to be more affected by urbanization than by climate change. Zhang et al. [22
] applied the improved SWAT model to simulate the impact of different land use changes on water balance in the North Johnston River catchment in eastern Australia, showing that urbanization will increase surface runoff. The change of underlying surface will lead to the increase of surface runoff and the decrease of precipitation infiltration recharge, causing the decrease of groundwater recharge amount. Correspondingly, the groundwater level will continue to drop when the groundwater exploitation remains unchanged or continues to increase. In this case, it may lead to surface subsidence and other geological hazards, threaten ecological security, water resources security [23
]. Thus, it is necessary to study the effect of land use change on the rule of runoff, rainfall infiltration coefficient and rainfall infiltration recharge, so as to reasonably plan the relationship between land use and water resources in the context of the social and economic development.
In order to evaluate the influence of underlying surface change on the hydrological cycle, we firstly analyzed the land use change in different periods of the study area, the Su-Mi-Huai District in Beijing, China, and used SWAT model to discuss the influence of underlying surface change on runoff mechanism and rainfall infiltration coefficient. Secondly, the semi-loose coupling model was established by MODFLOW and SWAT, and the results of this model were used to compare the influence of the water balance in the study area before and after land use changes in typical years. This study could provide guidance for the rational planning of land use, the correct prediction of urban water situation and the rational planning of water resources in areas with rapid urbanization.
Based on the Landsat 8 high-precision remote sensing data and the SWAT hydrological model, this study analyzes the change law of the falling water infiltration coefficient and surface runoff in the study area under the land use change scenario and analyzes the effect of land use change on the water balance of the study area using the MODFLOW model. The conclusions as follows are reached.
From 2000 to 2015, the land use change was mainly manifested in the transformation from cultivated land to urban and rural residential land in Su-Mi-Huai area in Beijing, China.
By 2015, the precipitation infiltration coefficient value in the area is smaller than its empirical value. In the area of increasing urban residential land, the precipitation infiltration coefficient decreased by 0.18–0.44. From 2000 to 2018, the average annual precipitation infiltration coefficient in the study area has gradually decreased, which is positively correlated with the change of cultivated land area and negatively correlated with the change of construction land.
Under the conditions of land use from 2000 to 2015, the annual average value of surface runoff and the runoff coefficient in the area showed an increasing trend. During the period of the fastest land use change (2000–2005), the increase values of surface runoff and annual average surface runoff of each year are the largest.
Changes in land use mainly reduce precipitation infiltration replenishment. In the dry year, precipitation infiltration recharge has the strongest response to land use changes, with a reduction rate of 38%.
This study examined the influence of hydrology cycle due to the land use change primarily caused by urbanization. The current study provides useful implications for the rational management of water resources under the situation of land use change caused by urbanization. The sustainable development of cities must consider the impact of land use change on the hydrological cycle and find a reasonable balance between urban planning and water resources management.