Upscaling Fill-and-Spill Hydrological Process in Cascading Wetland Networks

Abstract:

Runoff generation in low-gradient landscapes, where landscape storage features such as bogs, lakes, prairie sloughs, or surface depressions are dominated, is highly influenced by fill-and-spill hydrology. In these systems the local storage deficit and the degree and nature of connectivity between storage features control the contributing runoff area. This study set out to develop a closed-form analytical upscaled probabilistic event model of runoff response in large landscapes with thousands of wetland cascades. Individual wetland contributing area, runoff coefficient, and pre-event deficit of each wetland are defined by probability distributions based on the combination of spatial analysis and field observation.

The upscaled results provided by this model help to determine the effects of cascade depth, network branching ratio, gatekeepers, local contributing area, and deficit distribution on runoff response. It is also shown that the mathematical solution in this study is a generalization of the well-known PDM (Probability Distributed Model) and Xinanxiang probabilistic runoff models where the contributing area of each wetland and the cascading network are not included. The results of the proposed model may improve the ability of the current hydrological models to simulate runoff in wetland dominated basins influenced by fill-and-spill hydrology.