Showing papers by "Carl E. Zipper published in 2006"

Empirical modeling of hydrologic and nfs pollutant flux in an urbanizing basin1

Abstract: Long term effects of precipitation and land use/land cover on basin outflow and nonpoint source (NPS) pollutant flux are presented for up to 24 years for a rapidly developing headwater basin and three adjacent headwater basins on the urban fringe of Washington, D.C. Regression models are developed to describe the annual and seasonal responses of basin outflow and NPS pollutant flux to precipitation, mean impervious surface (IS), and land use. To quantify annual change in mean IS, a variable called delta IS is created as a temporal indicator of urban soil disturbance. Hydrologic models indicate that total annual surface outflow is significantly associated with precipitation and mean IS (r 2 = 0.65). Seasonal hydrologic models reveal that basin outflow is positively associated with IS during the summer and fall growing season (June to November). NPS pollutant flux models indicate that total and storm total suspended solids (TSS) flux are significantly associated with precipitation and urban soil disturbance in all seasons. Annual NPS total nitrogen flux is significantly associated with both urban and agricultural soil disturbance (r 2 = 0.51). Seasonal models of phosphorus flux indicate a significant association of total phosphorus flux with urban soil disturbance during the growing season. Total soluble phosphorus (TSP) flux is significantly associated with IS (r 2 = 0.34) and urban and agricultural soil disturbance (r 2 = 0.58). In urbanizing Cub Run basin, annual TSP concentrations are significantly associated with IS and cultivated agriculture (r 2 = 0.51).

Land Use Influences and Ecotoxicological Ratings for Upper Clinch River Tributaries in Virginia

Abstract: The Clinch River system of southwestern Virginia and northeastern Tennessee is among the most biodiverse aquatic ecosystems of the United States, but its fauna are in decline. Unionidae (freshwater mussel) species are a major component of the Clinch's aquatic community, and their decline is well documented. Point-source discharges within the Clinch drainage are few, and primary stressors on the biota are believed to originate from non-point sources that are transported into the mainstem by tributaries. Currently, the relative influences of tributaries as stressors on aquatic biota are unclear. We studied 19 major tributaries of the free-flowing Upper Clinch River, developed an Ecotoxicological Rating (ETR) utilizing eight parameters, and assessed stream quality among land use categories using the ETR rating system. Biological, toxicological, habitat, and chemical variables were measured in each tributary, near its confluence with the Clinch. Geographic Information System software was used to quantify land use within each tributary watershed; all tributary watersheds are predominately forested, but agricultural, mining, and developed land uses (urban, transportation) are also present. ETRs indicated that the tributaries draining mining-influenced watersheds had greater potential impact on the mainstem than those draining agricultural or forested watersheds, because of poor benthic macroinvertebrate scores. ETRs ranged from 44 to 63, on a 100-point scale, for mining-influenced tributaries compared to agricultural (57-86) and forested tributaries (64-91). Mean ETRs for the mining-influenced tributaries (51) were significantly different than ETRs from agricultural and forested streams (75 and 80, respectively), and the presence of developed land uses had no significant relationship with ETRs.

The ecotoxicological recovery of ely creek and tributaries (lee county, va) after remediation of acid mine drainage

Abstract: The Ely Creek watershed (Lee County, VA) was determined in 1995 to be the most negatively affected by acid mine drainage (AMD) within the Virginia coalfield. This determination led the US Army Corps of Engineers to design and build passive wetland remediation systems at two major AMD seeps affecting Ely Creek. This study was undertaken to determine if ecological recovery had occurred in Ely Creek. The results indicate that remediation had a positive effect on all monitoring sites downstream of the remediated AMD seeps. At the site most impacted by AMD, mean pH was 2.93 prior to remediation and improved to 7.14 in 2004. Benthic macroinvertebrate surveys revealed that one AMD influenced site had increased taxa richness from zero taxa in 1997 to 24 in 2004. While in situ testing of Asian clams resulted in zero survival at five of seven AMD influenced sites prior to remediation, some clams survived at all sites after. Clam survival was found to be significantly less than upstream references at only two sites, both downstream of un-mitigated AMD seeps in 2004. An ecotoxicological rating (ETR) system that combined ten biotic and abiotic parameters was developed as an indicator of the ecological status for each study site. A comparison of ETRs from before and after remediation demonstrated that all sites downstream of the remediation had experienced some level of recovery. Although the remediation has improved the ecological health of Ely Creek, un-mitigated AMD discharges are still negatively impacting the watershed.