SWAT Modeling for Depression-Dominated Areas: How Do Depressions Manipulate Hydrologic Modeling?

Abstract

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.

Modeling of spatiotemporal variations in runoff contribution areas and analysis of hydrologic connectivity

“…Finally, these topographic characteristics computed for all puddle levels are used in hydrologic modeling. For example, Tahmasebi Nasab, Singh, and Chu () utilized the D‐cubed algorithm as a tool to obtain topographic details and incorporated them into the Soil and Water Assessment Tools to improve hydrologic modeling in depression‐dominated areas. For this study, surface topographic characteristics obtained from the delineation process are used to analyze dynamic connectivity and CA.…”

Water–Soil–Vegetation Dynamic Interactions in Changing Climate

“…The new algorithms presented in four articles [39,40,44,45,48] provide necessary tools for better modeling effects of grazing on steppe grassland degradation, future climates on sedimentation at watershed scale, micro-topographic features (e.g., puddles) on hydrologic processes, and infiltration on the translational stability of long slopes. In addition, two articles [41,43] found that human activities were the primary reason for runoff reduction, whereas, another article [42] showed that climate variability was the dominant driver for decreasing trend of streamflow.…”

“…The articles cover a wide range of geographic regions across China [39][40][41][42][43][44]46,47,49,50] and the United States of America (USA) [45,48] with contrasting hydro-climate, soil, and vegetation conditions. Thus, the results presented in these articles can have global inferences: the data, analysis/modeling approaches, results, and findings will lay a solid foundation to further our scientific understanding of water-soil-vegetation interactions, ultimately leading to the development of practically effective solutions to sustaining the globe's ecosystem health and productivity.…”

“…The specific topics include steppe vegetation affected by climate change [39,40], interactions of climate, anthropogenic activities, and watershed hydrology [41][42][43], SWAT modeling for quantifying topography-controlled hydrologic processes and sediment yield [44,45], snow cover and frozen soil dynamics in cold regions [46], quantification of plant transpiration in arid/semiarid environment [47], coupled infiltration-runoff modeling for slope stability analysis [48], and assessment of nutrients in aquatic systems [49,50]. In terms of methodologies, these studies involve both field/laboratory experiments and mathematical modeling across different scales.…”

“…Tahmasebi Nasab et al [45] developed the PD-SWAT model that coupled the widely used SWAT with Puddle Delineation (PD) algorithm for hydrologic modeling in depression-dominated areas. The model incorporated topographic characteristics from the PD into SWAT at the hydrologic response unit (HRU) scale.…”