Simulating wetland-upland hydrological interactions in the Canadian boreal region

Abstract:

Wetlands play a substantial role in the hydrological cycle as they interact with the surrounding upslope area through the lateral exchange of groundwater. Many Land Surface Models (LSMs) are available to simulate the hydrological cycle; however, some processes (e.g. groundwater-surface water interaction) and landscape features (e.g. wetlands and hillslopes) are either missing or poorly represented. This problem can lead to errors in the simulation of different components of the water and energy balance, particularly streamflow and evapotranspiration. This study aims to develop an improved representation of upland-wetland interactions using a 1-D physically-based model by focusing on fens, which are mainly fed by groundwater discharge. We systematically investigate three approaches (three model’s versions) to represent lateral fluxes between hillslope and wetland. The three approaches represent the possible conditions of lateral water exchange between upland and wetland which are no exchange (uncoupled), one-way exchange (chained), and two-way exchange (fully coupled). The model is used to reproduce detailed field observations and calculate the fluxes into and out of the fen including periods of drought. Monte Carlo analysis is used to optimize the performance of the model’s three versions and evaluate the uncertainty and identifiability in the results. The models are used to investigate the behavior of the system under different spatial configurations and help to understand when and where the inclusion of dynamic coupled interactions between upland and wetland is essential.