Lorin Reinelt

Pollutant removal from stormwater runoff by palustrine wetlands based on comprehensive budgets

Comprehensive budgets of total suspended solids (TSS), total phosphorus (TP), total zinc (the most prevalent metal in urban runoff), and fecal coliforms (FC) were developed for two palustrine freshwater wetlands in Washington, USA. These budgets were based on input (inflow, precipitation, groundwater) and output (outflow, evaporation). One wetland received runoff from a primarily urbanized watershed (187 ha), whereas the other watershed (87 ha) was mostly rural and forested. Annual loadings to the urban wetland for TSS, TP, and zinc were 107, 0.63 and 0.43 kg ha−1 yr−1, respectively, based on watershed area. Corresponding loadings to the nonurban wetland were 30, 0.62 and 0.08 kg ha−1 yr−1. High TP input from groundwater at the nonurban wetland (82% of the TP input) resulted in overall loadings comparable to the urban wetland. Fecal coliform loadings were 4.2 · 1010 and 1.4 · 109 organisms ha−1 yr−1 for the urban and nonuran wetlands, respectively. Mean annual removal percentages (over the two-year study period) for TSS, TP, zinc, and FC were estimated at 14, 8, 31, and 49%, respectively in the urban wetland (2 ha). Corresponding removal rates in the nonurban wetland (1.5 ha) were 56, 82, 23, and 29%, respectively. Pollutant removal was influenced by season, flow conditions, residence time, pollutant source (surface versus groundwater), and pollutant state (solid versus dissolved). Results for the nonurban wetland showed that groundwater inputs were significant for TP loadings and removal.

A GIS method to aid in non-point source critical area analysis

Abstract The use of remote sensing techniques, image processing, computer mapping and overlays to make inventories of land use and to improve land and water management has increasing potential. Advantages of these techniques include greater geometric resolution and potential time and money savings. The increasing capabilities of personal computers and workstations (hardware and software) and the greater availability of databases have simplified the application of these techniques. In this application, a geographical information system (GIS) was used to facilitate the identification of critical non-point source areas of pollution by sediment-related nutrients. This critical source area information might then be used to aid in the development of non-point source control strategies or for monitoring programme design. This study shows the potential of using GIS in selecting critical source areas for sediment-related water quality problems and land resource protection.

Impacts of urbanization on palustrine (depressional freshwater) wetlands—research and management in the Puget Sound region

This paper summarizes the results of the Puget Sound Wetlands and Stormwater Management Research Program, which examined the impacts of urban stormwater on wetlands. Results are presented for data collected between 1988 and 1995 for 19 wetlands, showing changes in wetland hydrology resulting from urban conversion and the subsequent impacts on plant and amphibian communities. The amount of watershed imperviousness, the forested area, and the degree of outlet constriction were found to be the most significant factors affecting wetland hydroperiods. As hydroperiods changed, plant communities shifted towards communities adaptable to the new hydrograph. Wetlands with water level fluctuation above 20 cm resulted in lower plant richness in the emergent and scrub-shrub zones. Similarly, wetlands with water level fluctuation greater than 20 cm were significantly more likely to have low amphibian richness of three or fewer species. A primary goal of the research program was to employ the results to improve the management of both wetlands and stormwater in urban areas. Hydrologic guidelines were applied to King Countys basin planning and master drainage planning efforts. Controls that focused on minimizing impervious surfaces and maximizing forest retention in the wetland watershed proved to be the most widely usable strategy.

Non-point source water pollution management: Improving decision-making information through water quality monitoring*

The identification, assessment and management of non-point source water pollution problems can be improved through better water quality monitoring program designs. The result is often more useful and reliable information for use by decision-makers. In this study of the Svart River Basin in south-central Sweden, the results of a modified monitoring program, designed to address non-point source inputs, were compared with the results of the ongoing program. Cost, validity (addressing intended objectives) and reliability (estimated level of uncertainty) were the criteria used to evaluate and compare the design and results obtained from the two programs. The study showed that choices of variables measured, station location and sampling frequency have a direct influence on the type and value of information obtained, especially when considering non-point sources. For a similar cost, the modified program produced more valid and reliable information for decision-making than the ongoing program.

Estimation of nonpoint source loadings with data obtained from limited sampling programs

The feasibility of estimating nonpoint source loadings with data obtained from limited sampling programs was analyzed in conjunction with a study of sediment and nutrient loadings in a Swedish river basin. The study showed that different loading estimation methods can yield significantly different results, even if sampling during events (e.g. peak flows) occurs. This was particularly true for the temporal distribution of the estimated loadings. The estimated spatial distribution of loadings in the monitored subbasins was more independent of the applied estimation technique. Theoretical calculations showed that sampling strategies with evenly spaced sampling intervals may systematically over- or underestimate the true loading.The study basin was characterized by a pronounced snowmelt period and partly erosion-controlled nutrient loadings. Guidelines for the estimation of nonpoint loadings in such basins are summarized in a matrix. Factors influencing the choice of estimation method include the characteristics of the collected data, the relative influence of point sources, and the desired detail of loading estimates. Possible correlations between flow and concentration, and the presence of extreme events (and whether or not the events were sampled), also determine the appropriateness of the different methods.