Modeling hydrological controls on variations in peat water content, water table depth, and surface energy exchange of a boreal western Canadian fen peatland
Grant, Robert F.
Flanagan, Larry B.
American Geophysical Union
Improved predictive capacity of hydrology and surface energy exchange is critical for conserving boreal peatland carbon sequestration under drier and warmer climates. We represented basic processes for water and O2 transport and their effects on ecosystem water, energy, carbon, and nutrient cycling in a process-based model ecosys to simulate effects of seasonal and interannual variations in hydrology on peat water content, water table depth (WTD), and surface energy exchange of a Western Canadian fen peatland. Substituting a van Genuchten model (VGM) for a modiﬁed Campbell model (MCM) in ecosys enabled a signiﬁcantly better simulation of peat moisture retention as indicated by higher modeled versus measured R2 and Willmot’s index (d) with VGM (R2~0.7, d~0.8) than with MCM (R2~0.25, d~0.35) for daily peat water contents from a wetter year 2004 to a drier year 2009. With the improved peat moisture simulation, ecosys modeled hourly WTD and energy ﬂuxes reasonably well (modeled versus measured R2: WTD ~0.6, net radiation ~0.99, sensible heat >0.8, and latent heat >0.85). Gradually declining ratios of precipitation to evapotranspiration and of lateral recharge to discharge enabled simulation of a gradual drawdown of growing season WTD and a consequent peat drying from 2004 to 2009. When WTD fell below a threshold of ~0.35m below the hollow surface, intense drying of mosses in ecosys caused a simulated reduction in evapotranspiration and an increase in Bowen ratio during late growing season that were consistent with measurements. Hence, using appropriate water desorption curve coupled with vertical-lateral hydraulic schemes is vital to accurately simulate peatland hydrology and energy balance.
Sherpa Romeo green journal. Permission to archive final published version
Fen peatland , Peat water content , Peatland hydrology , Peat water content , Moisture retention , Peat drying , Energy balance , Surface energy exchange
Mezbahuddin, M., Grant, R. F., & Flanagan, L. B. (2016). Modeling hydrological controls on variations in peat water content, water table depth and surface energy exchange of a boreal western Canadian fen peatland. Journal of Geophysical Research (Biogeosciences), 121(8)m 2216-2242. doi:10.1002/2016JG003501