Climate change and anthropogenic activities do collectively lead to an alteration of the flow regime, posing a great influence upon the structure and persistence of native biotic communities within river ecosystems. The range of variability approach (RVA) method is commonly used to evaluate the flow regime alteration. However, it was reported to underestimate the degree of flow regime potentially. In this study, two new assessment methods/metrics for evaluating the process behaviors of the flow regime are developed based on Euclidean distance and dynamic time warping (DTW) distance. They are then integrated with the metric of RVA, generating two composite metrics that represent both frequency and process changes of the flow regime. The new methods/metrics were applied to identify the flow regime alteration in a typical basin in the middle reaches of the Yellow River, China. The results show that the composite metrics consistently reveal a high alteration degree of flow regime in the basin. The decreased biological integrity of fish demonstrates the reasonability of the high-level overall alteration to some degree. The updated methods enable more scientific evaluation for the complex hydrologic alteration under a changing environment.

The partial runoff is complicated in semi-arid and some semi-humid zones in terms of what the runoff generates in partial vertical positions. The partial runoff is highlighted by horizontal soil heterogeneity as well. How to identify the partial runoff and develop a variable threshold for runoff generation is a great difficulty and challenge. In this work, the partial runoff is identified by using a variable active runoff layer structure, and a variable soil water storage capacity is proposed to act as a threshold for runoff generation. A variable layer-based runoff model (VLRM) for simulating the complex partial runoff was therefore developed, using dual distribution curves for variable soil water storage capacity over basin. The VLRM is distinct in that the threshold for runoff generation is denoted by variable soil water storage capacity instead of infiltration capacity or constant soil water storage capacity. A series of flood events in two typical basins of North China are simulated by the model, and also by the Xinanjiang model. Results demonstrate that the new threshold performs well and the new model outperforms the Xinanjiang model. The approach improves current hydrological modelling for complex runoff in regions with large deficiencies in soil water storage.

The Kuye River Basin has experienced a rapid depletion of groundwater due to the increased coal production. In this study, by introducing the empirical equations derived from the three zone theory in the coal mining industry in China as a boundary condition, a calculation model was developed by coupling the soil and water assessment tool and visual modular three‐dimensional finite‐difference ground‐water flow model (SWAT‐VISUAL MODFLOW). The model was applied to several coal mines in the basin to quantify the groundwater impact of underground mining. For illustration purposes, two underground water observation stations and one water level station were selected for groundwater change simulation in 2009, producing the results that agreed well with the observed data. We found that groundwater level was closely related to the height of the fractured water‐conducting zone caused by underground mining, and a higher height led to a lower groundwater level. This finding was further supported by the calculation that underground mining was responsible for 23.20 mm aquifer breakages in 2009. Thus, preventing surface subsidence due to underground mining can help protecting the basin's groundwater.