Modeling Nitrogen and Carbon Dynamics in Wetland Soils and Water Using Mechanistic Wetland Model

Abstract

In this article, extension and application to variably-saturated wetland conditions of a processbased wetland model, namely WetQual is demonstrated. The new model described in this article is an improved version of an earlier model, which was only capable of capturing nutrient dynamics in continuously ponded wetlands. The upgraded model is capable of simulating nutrient cycling and biogeochemical reactions in both ponded and unsaturated zones of the wetland. To accomplish this goal, a comprehensive module for tracking water content in wetland soil was implemented in the model, and biogeochemical relationships were added to explain cycling of nitrogen (N) and carbon (C) in variably saturated zones of wetlands. The developed model was applied to a small, restored wetland receiving agricultural runoff, located on Kent Island, Maryland. On average, during the two year study period, the ponded compartment of the study wetland covered 65% of the total 1.2 ha area. Through mass balance analysis, it was revealed that the mass of nitrogen lost to denitrification at the variably saturated compartment of the study wetland was about 3 times higher than that of the ponded compartment (32.7 ± 29.3 kg vs. 9.5 ± 5.5 kg) whereas ammonia volatilization at the variably saturated compartment was a fraction of that of ponded compartment (1.2 ± 1.9 kg vs. 11.3 ± 11.8 kg). Sensitivity analysis showed that cycling of carbon related constituents in variably saturated compartment had high sensitivity to temperature and available soil moisture.

Non-floodplain Wetlands Affect Watershed Nutrient Dynamics: A Critical Review

“…We know a lot about individual wetland processes, and this knowledge has been integrated into individual wetland, or plot-scale, models. In fact, marked refinements have been made in recent years in simulating individual wetland nutrient biogeochemistry. , However, most watershed models have limited capacity to simulate both nutrient cycling in multiple NFWs across the landscape and the hydrological transport processes that link nutrient fluxes from NFWs to other surface waters , in part because of the complexity and variability of these processes.…”

Nutrient Removal Potential of Headwater Wetlands in Coastal Plains of Alabama, USA

“…The process-based WetQual model [ 26 , 28 – 30 ] was used to evaluate the pollutant removal efficiencies of the 44 selected wetlands. Due to the lack of observed discharge and loadings draining to each of these wetlands, the watershed-scale hydrologic model SWAT [ 27 ] was used to model terrestrial generation and transport of flow, , and phosphate .…”

“…Progress in modeling restored and engineered wetlands has outpaced that for natural wetlands. Much less progress has been made in process-based modeling of natural inland and coastal wetlands impacted by variably saturated soils or tidal effects (e.g., [ 25 , 26 ]). For instance, Sharifi et al [ 26 ] developed a process-based model capable of simulating nutrient cycling and biogeochemical processes in ponded and unsaturated wetland soils.…”