Assessing the Design and Maintenance Effects on Ecosystem Services Provided by Regional-Scale Green Stormwater Infrastructure.

摘要

Negative ecological effects of stormwater runoff are of increasing concern, especially in areas of rapid urbanization. Stormwater control measures (SCMs) such as constructed stormwater wetlands (CSWs) and wet retention ponds (ponds) are designed to provide multiple services to society (ecosystem services). This research was focused on design and maintenance impacts on ecosystem services provided by these regional-scale green infrastructure technologies.;In Chapter 3, the 'ripening' periods of different ecosystem system services were measured through the end of the second growing season at a CSW. The full potential of some ecosystem services were realized immediately such as volume reduction, TSS and NO2,3 treatment, while others were not fully developed until after the 1st growing season, e.g. TAN, ON, TN, and TP treatment. For the ecosystem services measured, ripening of the CSW was complete, with the realization of areal C densities and vegetation biodiversity, within one year of construction.;Chapter 4 focused specifically on evaluating the soil C sequestration services provided by ponds in three countries with substantially different climate characteristics: Southeast U.S., Singapore, and Sweden. This assessment established that ponds can sequester C; Singapore had the highest rate of accumulation (135 g C m-2 yr-1) among the climates sampled. Vegetation and at times Clay + Silt content were significant factors in C accumulation, and annual rainfall, or lack thereof, was also distinguished as an important C accumulation mechanism.;Previous studies have denoted decreased provision of regulating services over time, causing some concern among the regulated stormwater community. Chapter 5 investigated the opposite effects maturation and lack (absence) of maintenance have on CSWs to provide regulating services such as hydrologic mitigation and water quality improvement. Overall, water quality treatment improved, while hydrologic services provision were reduced over the 5-year period. In comparison to other SCMs, CSWs appear to have among the lowest operation and maintenance costs on a per unit of watershed basis.;Most regulatory agencies require a CSW to capture and slow release a single design storm's volume, thereby "awarding" it pollutant removal credit. This simplistic model ignores how CSW's actually treat pollutants , such as nitrogen, phosphorus, and sediment, and provides motivation for application of the P-k-C* model to describe CSW performance. These results (Chapter 2) (1) suggest there is an underlying unity of a number of complex processes and (2) support the model's intended use for conceptual analysis and as a design tool.;Vegetation establishment was discussed in Chapters 3, 4, and 5 to be a key design element for water quality treatment services; however, vegetation also potentially detracts from runoff storage volume of CSWs. Twelve CSWs and one hybrid wet pond were sampled in North Carolina during the peak plant growth season (summer) to assess how much volume vegetation occupies in the temporary storage zone. Other factors such as discrepancies between designed and as-built bathymetry probably have a much greater impact on the design volume loss when compared to that occupied by vegetation (<2%).