Modeling the Dynamics of Carbon Dioxide Emission and Ecosystem Exchange Using a Modified SWAT Hydrologic Model in Cold Wetlands

The restoration and protection of wetlands are crucial in reducing greenhouse gas emissions. In this research, the SWAT model was modified to investigate and estimate the groundwater table, net ecosystem exchange (NEE), and soil respiration impact on carbon dioxide (CO2) emission in the cold regions in Alberta. There is a lack of a process-based model that accounts explicitly for the CO2 emission and ecosystem exchange resulting from interactions between hydrological and biogeochemical processes. The SWAT model is modified to make unique contributions to wetlands by estimating CO2 emissions, soil temperature, and soil respiration that account for the dynamics of water tables and the relationship between subsurface and surface water storage. The modified model results predicted daily NEE with a very good model fit resulting in an R2 (Coefficient of determination), NSE (Nash-Sutcliffe Efficiency), PBIAS (percent bias), and RMSE (root mean square error) of 0.88, 0.72, 2.5, and 0.45 in the calibration period and 0.82, 0.67, −1.8, and 0.56 for the validation period, respectively. The prediction result indicated that the modified model performed well in predicting soil temperature, the groundwater table, and ecosystem respiration in the calibration and validation periods. In general, this study concluded that the modified model has the capability of representing the effects of water table dynamics on CO2 emissions and NEE in cold wetlands

Modeling the Dynamics of Carbon Dioxide Emission and Ecosystem Exchange Using a Modified SWAT Hydrologic Model in Cold Wetlands

The restoration and protection of wetlands are crucial in reducing greenhouse gas emissions. In this research, the SWAT model was modified to investigate and estimate the groundwater table, net ecosystem exchange (NEE), and soil respiration impact on carbon dioxide (CO2) emission in the cold regions in Alberta. There is a lack of a process-based model that accounts explicitly for the CO2 emission and ecosystem exchange resulting from interactions between hydrological and biogeochemical processes. The SWAT model is modified to make unique contributions to wetlands by estimating CO2 emissions, soil temperature, and soil respiration that account for the dynamics of water tables and the relationship between subsurface and surface water storage. The modified model results predicted daily NEE with a very good model fit resulting in an R2 (Coefficient of determination), NSE (Nash-Sutcliffe Efficiency), PBIAS (percent bias), and RMSE (root mean square error) of 0.88, 0.72, 2.5, and 0.45 in the calibration period and 0.82, 0.67, −1.8, and 0.56 for the validation period, respectively. The prediction result indicated that the modified model performed well in predicting soil temperature, the groundwater table, and ecosystem respiration in the calibration and validation periods. In general, this study concluded that the modified model has the capability of representing the effects of water table dynamics on CO2 emissions and NEE in cold wetlands

Modeling streamflow and sediment using SWAT in ethiopian highlands

The coincidence of intensive rainfall events at the beginning of the rainy season and unprotected soil conditions after extreme dry spells expose the Ethiopian Highlands to severe soil erosion. Soil and water conservation measures (SWC) have been applied to counteract land degradation in the endangered areas, but SWC efficiency may vary related to the heterogeneity of the landscape. The Soil and Water Assessment Tool (SWAT) model was used to model hydrology and sediment dynamics of a 53.7 km2 watershed, located in the Lake Tana basin, Ethiopia. Spatially distributed stone bund impacts were applied in the model through modification of the surface runoff ratio and adjustment of a support practice factor simulating the trapped amounts of water and sediment at the SWC structure and watershed level. The resulting Nash-Sutcliffe efficiency (NSE) for daily streamflow simulation was 0.56 for the calibration and 0.48 for the validation period, suggesting satisfactory model performance. In contrast, the daily sediment simulation resulted in unsatisfactory model performance, with the NSE value of 0.07 for the calibration and –1.76 for the validation period and this could be as a result of high intensity and short duration rainfall events in the watershed. Meanwhile, insufficient sediment yield prediction may result to some extent from daily based data processing, whereas the driving runoff events and thus sediment loads occur on sub-daily time scales, probably linked with abrupt gully breaks and development. The calibrated model indicated 21.08 Mg/hm2 average annual sediment yield, which is far beyond potential soil regeneration rate. Despite the given limits of model calibration, SWAT may support the scaling up and out of experimentally proven SWC interventions to encourage sustainable agriculture in the Ethiopian Highlands