| Title: | SWAT modeling for depression-dominated areas: How do depressions manipulate hydrologic modeling? |
| Authors: | Nasab, M.T., V. Singh and X. Chu |
| Year: | 2017 |
| Journal: | Water |
| Volume (Issue): | 9(1) |
| Pages: | |
| Article ID: | 58 |
| DOI: | 10.3390/w9010058 |
| URL (non-DOI journals): | |
| Model: | PD-SWAT & SWAT |
| Broad Application Category: | hydrologic only |
| Primary Application Category: | depressional (pothole, wetland or pond) effects and/or processes |
| Secondary Application Category: | model and/or data comparison |
| Watershed Description: | 1,813 km^2 tributary of the Pipestem River, located in North Dakota, U.S. |
| Calibration Summary: | |
| Validation Summary: | |
| General Comments: | |
| Abstract: | Modeling hydrologic processes for depression-dominated areas such as the North American
Prairie Pothole Region is complex and reliant on a clear understanding of dynamic
filling-spilling-merging-splitting processes of numerous depressions over the surface. Puddles are
spatially distributed over a watershed and their sizes, storages, and interactions vary over time.
However, most hydrologic models fail to account for these dynamic processes. Like other traditional
methods, depressions are filled as a required preprocessing step in the Soil and Water Assessment Tool
(SWAT). The objective of this study was to facilitate hydrologic modeling for depression-dominated
areas by coupling SWAT with a Puddle Delineation (PD) algorithm. In the coupled PD-SWAT
model, the PD algorithm was utilized to quantify topographic details, including the characteristics,
distribution, and hierarchical relationships of depressions, which were incorporated into SWAT
at the hydrologic response unit (HRU) scale. The new PD-SWAT model was tested for a large
watershed in North Dakota under real precipitation events. In addition, hydrologic modeling of a
small watershed was conducted under two extreme high and low synthetic precipitation conditions.
In particular, the PD-SWAT was compared against the regular SWAT based on depressionless DEMs.
The impact of depressions on the hydrologic modeling of the large and small watersheds was
evaluated. The simulation results for the large watershed indicated that SWAT systematically
overestimated the outlet discharge, which can be attributed to the failure to account for the hydrologic
effects of depressions. It was found from the PD-SWAT modeling results that at the HRU scale surface
runoff initiation was significantly delayed due to the threshold control of depressions. Under the high
precipitation scenario, depressions increased the surface runoff peak. However, the low precipitation
scenario could not fully fill depressions to reach the overflow thresholds in the selected sub-basins.
These results suggest the importance of depressions as gatekeepers in watershed modeling. |
| Language: | English |
| Keywords: | improved SWAT modeling; puddle delineation; potholes; depressions; threshold control |