Improving soil moisture accounting and streamflow prediction in SWAT by incorporating a modified time‐dependent Curve Number method

Abstract

Abstract:The objective of this study is to incorporate a time-dependent Soil Moisture Accounting (SMA) based Curve Number method (SMA_CN) in Soil and Water Assessment Tool (SWAT) and compare its performance with the existing CN method in SWAT by simulating the hydrology of two agricultural watersheds in Indiana, USA. Results show that fusion of the SMA_CN method causes decrease in runoff volume and increase in profile soil moisture content, associated with larger groundwater contribution to the streamflow. In addition, the higher amount of moisture in the soil profile slightly elevates the actual evapotranspiration. The SMA-based SWAT configuration consistently produces improved goodness-of-fit scores and less uncertain outputs with respect to streamflow during both calibration and validation. The SMA_CN method exhibits a better match with the observed data for all flow regimes, thereby addressing issues related to peak and low flow predictions by SWAT in many past studies. Comparison of the calibrated model outputs with field-scale soil moisture observations reveals that the SMA overhauling enables SWAT to represent soil moisture condition more accurately, with better response to the incident rainfall dynamics. While the results from the modification of the CN method in SWAT are promising, more studies including watersheds with various physical and climatic settings are needed to validate the proposed approach.

Rationale and Efficacy of Assimilating Remotely Sensed Potential Evapotranspiration for Reduced Uncertainty of Hydrologic Models

“…Evapotranspiration, the largest outgoing component in the hydrologic cycle, regulates soil moisture accounting (SMA; Long et al, ; K. C. Wang & Dickinson, ), which in turn affects the accuracy of surface/subsurface runoff simulation in a hydrologic model (M. A Rajib & Merwade, ). Precipitation input is the supply of water from atmosphere to land surface, whereas potential evapotranspiration (PET) is the index of demand that drives water back to atmosphere when sufficient water and energy are available.…”

Spatiotemporal Impacts of Climate, Land Cover Change and Direct Human Activities on Runoff Variations in the Wei River Basin, China

“…It is a process-based, continuous-time, semi-distributed hydrology and sediment simulator that can model complex watersheds with diverse weather, land cover, soils and topography conditions over a long period of time and various time steps at the large basin scale [27]. SWAT has been successfully used to simulate the hydrological cycle in various regions all over the world [28][29][30][31][32][33]. Previous studies have shown that SWAT can reflect the spatial heterogeneity of a watershed's climatic factors and underlying surface composition.…”

Spatial and Temporal Evaluation of Hydrological Response to Climate and Land Use Change in Three South Dakota Watersheds

“…(), SWAT simulations matched well with the observed, except for few high‐flow events (Figure ). This is comparable to findings from many past studies across different regions, reporting imprecise performance of SWAT model in extreme flow conditions ( e.g ., Vazquez‐Amábile and Engel, ; Arabi et al ., ; Larose et al ., ; Wang et al ., ; Oeurng et al ., ; Qiu and Wang, ; Rajib and Merwade, ; Rajib et al ., ). The goodness‐of‐fit scores ( R 2 , NSE, and PBIAS) are presented in Table , separately for calibration, validation, and the entire study periods.…”

“…A prior parameter sensitivity analysis was performed in this study (not shown here); accordingly, a comprehensive list of 19 parameters (common to all the six models; Table ) representing the land surface, subsurface, channel routing, and snowmelt processes were directly included in the parameter optimization process. SWAT parameters and their initial value ranges (see Table ) were selected based on the review of existing literature on nearby Midwestern agricultural watersheds ( e.g ., Jha et al ., ; Folle, ; Hutchinson and Christiansen, ; Neupane and Kumar, ; Rajib et al ., ) and suggestions from model developers (Neitsch et al ., ; Abbaspour, ). Nash‐Sutcliffe efficiency (NSE) was used as objective function to measure the agreement between simulated and observed streamflow hydrographs.…”