Improvement and comparison of the rainfall–runoff methods in SWAT at the monsoonal watershed of Baocun, Eastern China

Abstract

A new physics-based rainfall-runoff method of SWAT was developed, which integrates a water balance model (WB proposed by White et al. (2011)) with the variable source area (WB-VSA). This approach was further compared with four methods -soil-water-dependent curve number (CN-Soil), evaporation-dependent curve number (CN-ET), Green and Ampt equation (G&A) and WB -in a monsoonal watershed, Eastern China. The regional sensitivity analysis shows that volumetric efficiency coefficient (VE) with river discharges is sensitive to the most Downloaded by [New York University] at 06:36 01 August 2015A c c e p t e d M a n u s c r i p t 2 parameters of all approaches. Results of model calibration against VE demonstrate that WB-VSA is the most accurate owing to reflection of the spatial variation of runoff generation affected by topography and soil properties. Other methods can also well mimic baseflow, but G&A and CN-ET simulate floods much worse than the saturation excess runoff approaches (WB-VSA, WB and CN-Soil). Meanwhile, CN-Soil as an empirical method fails to simulate groundwater levels.By contrast, WB-VSA captures them best.

Simulating saturation‐excess surface run‐off in a semi‐distributed hydrological model

“…African catchments mainly prompted this study, it has also been noted that other modellers have recently addressed similar issues with other models (Boll, Brooks, Crabtree, Dun, & Steenhuis, 2015;Cheng et al, 2016;Woodbury, Shoemaker, Easton, & Cowan, 2014).…”

“…The new process referred to is the generation of surface run‐off due to saturation excess. Although some recent experiences of applying the model in southern African catchments mainly prompted this study, it has also been noted that other modellers have recently addressed similar issues with other models (Boll, Brooks, Crabtree, Dun, & Steenhuis, ; Cheng et al, ; Woodbury, Shoemaker, Easton, & Cowan, ).…”

Improved Curve Number Estimation in SWAT by Reflecting the Effect of Rainfall Intensity on Runoff Generation

“…However, there are some controversies with this method: it is not physically based, it lacks complete historical documentation, and it inadequately represents variable source areas (VSA). It also provides inadequate consideration of the rainfall intensity and duration on runoff generation [2,[11][12][13]. Many researchers have proposed adjustments to the CN model to better capture runoff dynamics [8,12,[14][15][16][17].…”

“…It also provides inadequate consideration of the rainfall intensity and duration on runoff generation [2,[11][12][13]. Many researchers have proposed adjustments to the CN model to better capture runoff dynamics [8,12,[14][15][16][17]. For example, White et al [15] found that temporal CN adjustments resulted in more accurate simulations, when the CN in the Soil and Water Assessment Tool (SWAT) was changed seasonally to account for variation of watershed storage due to changes in plant growth and dormancy.…”

“…They found that the newly modified SWAT (SWAT-WB) significantly improved model predictions in monsoonal climates due to its ability to provide a more realistic distribution of saturated areas (and thus runoff source). The SWAT-WB model was further modified with variable source areas (WB-VSA) by Cheng et al [12]. The WB-VSA model was compared with four other rainfall-runoff methods (including the soil-water-dependent curve number (CN-Soil), the evaporation-dependent curve number (CN-ET), the G and A equation, and the SWAT-WB) using data from a monsoonal watershed in Eastern China.…”