Water cycle evolution in the Haihe River Basin and its relationship with landscape pattern changes

Landscape patterns and water cycle processes have changed significantly in recent decades as a result of intensive interference from human activities. Although the intensification of the global water cycle is well illustrated from a climate change perspective, using landscape index to characterize the evolution of water cycle have been less explored. This study aimed to investigate the water cycle status and its evolution from the perspective of landscape patterns. A water cycle intensity (WCI) evaluation model based on the landscape index was developed. Defined as the ratio of the water resource circulation to the natural circulation, the WCI was used to analyze the water cycle evolution trend in each region of the Haihe River Basin. Through correlation and dynamic change trend analyses, the patch density (PD) of the urban areas and runoff landscape index (RLI) were identified as synchronizing with the WCI changes. The mathematical relationships between the landscape indicators (PD and RLI) and WCI were explored. Thereafter, according to the WCI development and its impact on the ecological environment, three categories of water cycle statuses (WCSs) were proposed: the natural circulation status (NCS), moderately developed status (MDS), and overdeveloped status (ODS). The WCS evolution trend in the Haihe River Basin was evaluated and the results showed all regions have evolved into a state of ODS with WCIs above 35% in 2010 and five of the plain regions greater than 80%. The proposed approach can be effectively applied to evaluating and predicting WCS in ungauged basins or future landcover scenarios, thereby providing a new perspective and effective tools for water resource management.