We first performed a single-point LSM simulation in the fen site in North Saskatchewan. Two modifications were tested: first, the modified\(F_{\text{sat}}\) formula and, second, a sensitivity test for surface water dynamics with various storage capacities. Figure 4 shows the\(F_{\text{sat}}\) parameter, energy and water balance in the fen site simulated by Noah-MP. In Figure 4a, the default \(F_{\text{sat}}\)formula using the exponential function of the water table depth fails to represent the large magnitude and strong seasonal variation, as shown by the GIEMS data. The modified formula using the first layer of soil moisture improves both the magnitude and seasonal cycle of the\(F_{\text{sat}}\) parameter. This larger \(F_{\text{sat}}\) effectively changes the surface water partitioning, by increasing the surface runoff, which leaves the grid point water balance, and reducing the infiltration to soil moisture, which further reduces ET and underground runoff (Figure 4b). Furthermore, the increased \(F_{\text{sat}}\)reduces latent heat fluxes and enhances sensible heat fluxes from March to September, with the strongest decrease in July (Figure 4c).

The surface wetland scheme (Section 2.4) collects the increased surface runoff in wetland storage and allows evaporation to the atmosphere. The scheme’s contribution to surface water and energy balance depends on its storage capacity. Figure 4d shows the sensitivity of water storage in a wetland with four different capacities (WS=0, 5, 50 and 500 mm). When wetland storage = 5 mm (“WS=5”), the wetland water would be depleted during the summer, while with larger capacity (WS=50 or 500), the water storage from the previous year can be sustained through dry seasons. Greater water-holding capacity allows greater contribution to evaporation and reduces surface runoff (Figure 4e). The changing storage capacity has little impact on underground runoff. Moreover, greater storage capacity also allows greater latent heat flux and less sensible heat flux. The effect threshold lies between WS=5 and WS=50, as water may be dried in smaller capacities, while the contribution is similar between WS=50 and WS=500.