Modeling the subsurface hydrology of mer bleue bog

In this study, the ecosys model was used to simulate the hydrology of the Mer Bleue bog, Ontario, Canada, with seasonally varying water tables in the upper 1 m. The soil profile was divided into three zones of peat (fibric, hemic, and sapric). In the model, large, readily drained macropore fractions in the fibric peat caused low water-holding capacity and high infiltration rates, in contrast to hemic and sapric peat, with small macropore fractions, high water-holding capacities, and low infiltration rates. Model results for peat water contents, θ, and water table depths, Z, were tested with continuous hourly measurements from 2000 to 2004 using time domain reflectometry probes and piezometers. Within the zone of pronounced water table variation, the θ and Z modeled with the Hagen-Poiseuille equation for macropore flow and Richards' equation for peat matrix flow corresponded better to the measured θ and Z (regression slopes between 0.62 and 1.03, intercepts between -0.05 and 0.02 m3 m-3, and R2 between 0.40 and 0.56), than did the modeled θ and Z with Richards' equation alone (regression slopes between 0.33 and 1.43, intercepts between 0.11 and 0.22 m3 m-3, and R2 between 0.27 and 0.41). The Richards equation alone, even when parameterized with extremely high or low bulk saturated hydraulic conductivities of fibric peat, modeled slower infiltration, greater water retention, and lower Z than measured. The implications of macropore flow might be of great importance for peatland hydrology, therefore this experimental and modeling work should be extended to other wetlands as well