Simple approach for groundwater level modelling for wetland restoration planning

The restoration and stabilization of the hydrological regime is essential part in the peatland restoration for climate change mitigation – reduction of greenhouse gas emissions. Essential parameter to evaluate the success of the restoration is the median water table depth. It can be derived from hydrological modelling, but fully coupled modelling is complex and time consuming. Here we report on a simplified approach to simulate the likely outcomes of the hydrological restoration of a temperate floodplain wetland in Latvia, Norther Europe. We subdivided the model territory into 10 m size gird cels and apply a one-dimensional water balance model with daily time step for each of the cells. The model was forced by precipitation and evapotranspiration data derived from ERA5-land reanalysis and river water level from nearby gauging station. The groundwater filtration to the nearest ditch was calculated from water table gradient, assuming stationary conditions and using the water table as input from the previous model time step. The simple model can reasonably accommodate surface water pooling as well as timing of minimum and maximum water levels. In comparison to two-year period the model RMSE was 0.13 to 0.17 m while MSD -0.08 to 0.07 m. The simple approach can provide reasonable forecasts of management scenarios for restoration planning and carbon farming projects, without the need for fully coupled hydrological modelling.