Rainfall–Runoff Processes and Modelling in Regions Characterized by Deficiency in Soil Water Storage

Abstract

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.

A Statistical Vertically Mixed Runoff Model for Regions Featured by Complex Runoff Generation Process

“…The XAJ [11], SBM [19], VMM [34] and VLRM [3] models are chosen as typical models of flood forecasting to compare with the Statistical Vertically mixed Hydrological Model (SVHM) model developed in this work. XAJ, SBM, VMM and VLRM are selected as representative of saturation-excess based models, infiltration-excess based models, mixed runoff models and partial saturation-excess based models, respectively.…”

“…Rainfall-runoff models are basic and important tools for flood forecasting [1][2][3]. Reliable and accurate flood forecasts by rainfall-runoff models are important for efficient reservoir operation, river management, flood control and warning [4][5][6][7][8].…”

“…For instance, the semidistributed Xinanjiang (XAJ) model developed by Zhao [11] is widely used in humid areas in China and other regions worldwide [12][13][14][15]. The main feature of XAJ model is the concept of saturation-excess, which means that runoff is not produced until the soil moisture content of the unsaturated zone reaches field capacity [3,11]. The semidistributed TOPMODEL (topography based hydrological model) was developed by using a variable source area concept that assumes the runoff generates on repletion of storage at the source areas [16].…”

“…There is generally no stable dominated runoff component or runoff mechanism in these regions [21,22]. Hydrological modeling in these regions thus has been suffering poor efficiency, thereby handicapping the reasonable streamflow simulation, flood forecasts and warning [3,[21][22][23][24].…”

“…The classical single runoff yielding pattern seems powerless in simulating the complex runoff generation process. The variable layer-based runoff model (VLRM) [3] try to simulate runoff generation process based on a new partial saturation-excess concept, which captures the complex runoff even the unsaturated zone is not totally saturated but neglects the infiltration-excess surface runoff component. It is theoretically unsuitable for the regions with dominated infiltration-excess surface runoff.…”