Land-use and land-cover (LULC) change has direct impacts on ecosystems and their associated services, particularly on water yield (WY). WY is the total amount of water that runs off the ground within a region [1
]. The regular distribution of WY is essential to the hydrological balance, since a decrease may result in water scarcity and a sharp increase causes flooding [2
]. Studies have demonstrated that LULC change can modify the underlying mechanisms of transferring rainfall to WY through altering an ecosystem’s hydrological characteristics such as infiltration, evapotranspiration, and groundwater recharge capacity [3
]. Therefore, in response to LULC changes, WY variation reflects the hydrological services of different land ecosystems.
Many researchers have explored the effects of LULC changes on WY over a range of spatial and temporal scales [4
]. In general, these studies have focused on the impact of LULC change on total WY over a certain time span [7
] and/or WY responses to a typical LULC type, such as forest, cropland, or built-up land (urbanization/commercial land) [9
]. Little attention has been given to quantative evaluation on the WY capacities of different LULC types. Quantifying WY specific to individual LULC type is not only useful to the after-event analysis, but also crucial to improve the predictability of WY responses to LULC dynamics, which will facilitate future integration of LULC planning and water resource management.
In the past, studies investigating the impact of LULC change on WY have been mainly based on paired catchment experiments. However, it is difficult to locate two catchments with similar characteristics in terms of slope, area, soil, climate and vegetation. Strict selection criteria restrict the studies to a small scale. In addition, those experiments are time consuming and the results are sometimes contradictory [10
]. Zhou et al. [14
], for example, pointed out the opposite findings from two similar experiments in China’s Yangtze River basins: one found out that there was a significant increase in WY as a result of the clearing of forest; in contrast, the other concluded that the WY increased greatly after afforestation. In recent years, models for ecosystem service evaluation have been developed. They generally have the characteristics of ease of use, using globally available data, accepting spatially explicit inputs and producing spatially explicit outputs, and limiting the model structure to key biophysical processes involved in LULC change [15
]. The InVEST (Integrated Valuation of Environment Services and Tradeoffs) model was developed in line with this philosophy. Based on the different LULC scenarios, InVEST provides a way of evaluating WY from an ecosystem services perspective [16
]. The WY suite of InVEST is designed to simulate the annual biophysical contribution of LULC to WY. It is flexible for use with regards to scale (local, regional or global), data input, assessment, and mapping details, and could provide more direct and visual results for decision-making support [17
The Jing-Jing-Ji region in the northern semi-arid China (Figure 1
) is the abbreviation for the capital city Beijing (Jing) and its neighboring areas Tianjin (Jin) and Hebei (Ji). The region is the third largest economic center after the Yangtze River delta region and the Pearl River delta region in China [20
]. However, Jing-Jin-Ji has been suffering increasing water scarcity [21
]. The annual water resource per capita decreased from about 300 m3
per capita in 1990 to 143 m3
per capita in 2015 [24
]. The average annual water deficit increased from 6.5 billion m3
during the period from 1990 to 1999, to around 7.4 billion m3
for the period from 2000 to 2015 [25
]. Over-exploitation of water in the region has resulted in serious ecological deterioration [27
]. On the other hand, urban flooding events have frequently occurred in recent years, of which the most catastrophic were the “7.21” flood in Beijing city on 21 July 2012 and the “7.19” flood in Xingtai city of Hebei province on 19 July 2016. The region, therefore, is in a situation with a paradoxical coexistence of increased water scarcity and urban flooding [28
]. The paradox in the Jing-Jin-Ji region stimulated many hydrological and hydraulic studies, of which the majority focused on the influences of LULC changes on WY at the individual river basin level for the Hai river, Luan river, Miyun reservoir, Chaobai river, and Baiyangdian river [8
]. However, there is a lack of quantitative analysis of the relationship between LULC change and WY for the whole Jing-Jin-Ji region.
Focusing on the Jing-Jin-Ji region, the primary aim of our study is to provide fundamental knowledge for sustainable LULC planning and water resource management. The specific objectives of this study are to: (1) evaluate the spatial-temporal changes of the WY response to climatic variation and LULC change over the period of 1990 to 2015; (2) identify the impacts of LULC changes on WY by assessing LULC change scenarios with the InVEST model; and (3) define and analyze the WY coefficients of various LULC to predict WY for future LULC planning.