Incorporating the Filling–Spilling Feature of Depressions into Hydrologic Modeling

Abstract

Surface depressions are one of the important impact factors of hydrologic processes and catchment responses. However, in many hydrologic models, the influence of depressions is often simulated in a lumped manner, which results in the insufficient characterization of the filling–spilling–merging–splitting dynamics of depressions and the threshold behavior of the overland flow. The objective of the research reported in this paper is to improve the simulation of depression-influenced hydrologic processes by capturing the threshold control of depressions. To achieve this objective, a Depression-oriented Soil and Water Assessment Tool (SWAT-D) is developed. Specifically, the intrinsic changing patterns of contributing area and depression storage are first determined and further incorporated into the SWAT to simulate the filling–spilling of depressions and depression-influenced overland flow dynamics. The SWAT-D was applied to a depression-dominated watershed in the Prairie Pothole Region to evaluate its performance and capability. The simulated and observed hydrographs at the watershed outlet showed good agreement, with only a 7% deviation between the simulated and observed volumes of discharges in 2004. The NSE values for the simulated monthly average discharges during calibration and validation periods were 0.78 and 0.71, respectively, indicating the ability of the SWAT-D in reproducing the depression-influenced catchment responses. In addition, the SWAT-D was compared with other depression-oriented modeling techniques (i.e., the lumped depression approach and probability distribution models), and the comparisons emphasized the improvement of the SWAT-D and the importance of the research reported in this paper.

Incorporating Wetland Delineation and Impacts in Watershed-Scale Hydrologic Modeling

“…The algorithm of HUD-DC was primarily based on the depression-oriented delineation methods [37][38][39]. The related delineation approaches and algorithms have been widely tested over a decade in a series of depression-oriented hydrologic modeling studies (e.g., [33,[37][38][39][40][41][42][43]). Based on both the original DEM and the fully filled DEM, HUD-DC identifies depressions, channels, and their contributing areas as two types of hydrologic units (i.e., puddle-based units and channel-based units), as well as the connectivity between the hydrologic units.…”

“…Similar issues were also observed by Tahmasebi Nasab et al [55], Zeng et al [30], and Shabani et al [49] in their SWAT applications. The model's performance was also affected by the lumped methods (e.g., SCS-CN) in the daily SWAT modeling [56] and the simplifications in the semi-distributed, watershed-scale model [41].…”