Evaluating management options: Simulating wetland processes and performance of nutrient reduction by use of a water quality algorithm.

摘要

The effects of nutrient overloading have been well identified in areas such as the Gulf of Mexico, where agricultural drainage from the Midwest is considered a main contributor to the hypoxic zone. Amongst the suite of agricultural Best Management Practices (BMPs), managed wetlands may present a more cost effective approach to assimilate pollutants and improve water quality at the scale of small watersheds. However, previous research has yielded varying results. Mathematical models have become a tool used to characterize components and predict behaviors of a given process. Model results can then be used to analyze multiple management options, improve decision making, and potentially reduce costs. This research evaluates multiple management options at a natural wetland by developing and implementing a wetland water quality algorithm within the Variable Infiltration Capacity (VIC) model.;The successful implementation of the water quality algorithm enabled the following management options to be further explored for nitrate and soluble reactive phosphorous (SRP) reduction: 1) establishing plant variety within the wetland, 2) management of water level to increase water storage, and 3) water storage and reuse for crop irrigation. Model simulation results revealed that water storage is the best management option for nitrate reduction with a decrease in load of 34.7%. Though caution should be taken during its operation to appropriately manage desorption processes increasing SRP concentration. The best management option for SRP reduction was the implementation of wetland species with high plant uptake values similar to that of the Iris pseudacorus L. (paleyellow iris), which reduced the SRP load by 47.1%. The overall best management option is water storage and reuse for crop irrigation which provides both environmental and economic benefits by revealing the following: an increase in wetland area by 68.6%, a decrease in nitrate and SRP load by 32.4% and 8.0% respectively, while maintaining water within the wetland and irrigating up to a 20 acre field. Ensuring pumping rates are set at a sustainable level is also important to avoid reducing the hydroperiod and causing potential harm to the surrounding ecosystem.