Watershed Science and Management Unit
Department of Forestry
Southern Illinois University Carbondale
Links:
Evaluating Watershed Health Risks through Integrated Water Quality Analyses, Community Capacity Assessments, and Outreach Appraisals
Mae Davenport, Jon Schoonover, Karl Williard, Erin Seekamp, and
Joan Brehm
Many Illinois watersheds have been identified as degraded. However, what anthropogenic factors contribute to water resource impairment and how local communities might best plan and manage for watershed conservation are less understood. We propose an interdisciplinary investigation of water quality and community capacity to evaluate and in turn, communicate watershed and community health risks. Specifically, water quality analysis, capacity assessments, and outreach appraisals will be conducted in eight subwatersheds (two urban and six rural) in the Lower Kaskaskia River. Several water resource impairment indicators and causes will be examined including sediment and nutrient loads, pathogens, eutrophication, flooding, land cover, and development patterns. Six community capacity indicators will be examined including community leadership, institutional support, community resources, social cohesion, shared vision, and collective action. Based on the health risk evaluations, three innovative outreach techniques—interactive workshops, traveling exhibits, and an integrated website—will be developed for the subwatershed communities and appraised for their effectiveness. The project also serves as an education tool for students who will gain experience in water quality and social data collection and outreach program development. From study design to outreach implementation, a participatory approach will be taken that informs and empowers diverse stakeholders by integrating their perspectives and life experiences throughout the project. Recommendations for integrating effective watershed conservation, community capacity building, and outreach strategies will be provided for each subwatershed community in a management plan. The study will enable policy makers to equitably prioritize and target watersheds for conservation programs and identify key steps in mobilizing community support.
Evaluation and management of surface hydrology, erosion, and sedimentation associated with tracked and wheeled vehicle training
Karl Williard, Jon Schoonover, John Groninger, James Zaczek, and
Charles Ruffner
The proposed 3-phase project is designed to assess, manage, and mitigate erosion and sedimentation associated with tracked and wheeled vehicle training in areas 9 and 10 in the Ft. Knox military installation. Phase 1 (i.e., years 1-3) will provide an extensive physical and biotic site characterization of the plateau, eroded gullies, adjacent side slopes, and Otter Creek floodplain that are potentially impacted by military activities in the training areas. Pilot Best Management Practices (BMPs) will also be designed and installed during phase 1; including, a vegetated retention basin and a gully stabilization demonstration. These features will serve as pilot studies as well as demonstration tools to assess the utility and feasibility of proposed practices prior to more extensive installation in later phases. During phase 2 (year 4), BMPs will be installed in the areas prioritized as the most susceptible to erosion and sediment loss. The final phase of the project (i.e., phase 3) will provide a post-BMP assessment of erosion, sediment delivery, and biotic integrity. The cost- and long-term practical-effectiveness of the implemented BMPs will also be ascertained during this phase.
Growing Economic and Environmental Applications of Giant Cane as a Best Management Practice
Jon Schoonover and James Zaczek
There is great unsupplied demand for agricultural development of sustainable bioenergy sources and innovative products for the economic and environmental security of our nation and the world. Increased development of bioenergy can pose risks to the environment in the form of losses of habitat and native species and the potential degradation of water quality associated with intensive cultural systems. Opportunities exist to develop sustainable agricultural alternatives to compliment and enhance traditional systems. Cultivated plants are being used as biofuels, biofilters, and for carbon sequestration, however, few native species have had intensive evaluations of their agricultural potential and environmental benefits. We propose to expand SIU’s ongoing giant cane (Arundinaria gigantea) research to develop the applications of giant cane in agriculture and habitat conservation. We will collect and propagate varieties of our native cane species and further determine its agricultural utility for biomass/bioenergy production, filter strip/water quality enhancement and wildlife habitat. Further we will disseminate research findings and provide access to the genetically selected plant materials for public use.
Giant cane is a native woody grass that historically dominated southern Illinois floodplains in naturally existing expansive stands or canebrakes. Wildfire suppression and land use changes forced cane to exist in small sporadic communities with less than 2% remaining across its native range. Although this species has not yet been thoroughly researched, bamboos have diverse utility as foods for humans and livestock, fiber products, horticultural plants, and for environmental applications. Giant cane has proven to be an agriculturally compatible riparian buffer species as an effective filter of nutrients and sediment from agriculture surface and subsurface runoff, a high quality forage, and critical habitat for over 50 species of wildlife. Since several rare wildlife species depend on cane habitat, specifically Swainson’s Warbler, swamp rabbit, canebrake rattlesnake, and various insects, many local, state, and federal government agencies and nature-based organizations have developed programs and provide support to promote giant cane restoration. However, the primary hurdle facing the restoration efforts is acquiring cane planting stock. Thus, a goal of this research is to develop a sustainable source of propagules for future giant cane restoration, while characterizing the growth and development of diverse giant cane varieties or provenances, its biofuel attributes, and carbon sequestration capacity. The proposed nursery would provide economic return, expand giant cane research, provide a unique resource for leveraging future support and serve as a public demonstration area.
A Watershed-scale Assessment of the Water Quality Impacts of Riparian Buffers in Southern Illinois
Jon Schoonover and Karl Williard
A paired-watershed approach is being implemented to investigate the long term benefits of riparian buffers in agricultural watersheds. Three watershed have been instrumented with Parshall flumes, pressure transducers, and ISCO automated water samplers to monitor stream stage and water quality. Channel morphology will also be assessed annually throughout the duration of the project.
Assessment of concentrated flow and sediment attenuation within riparian buffer strips
Ryan Pankau
Riparian buffer strips are important conservation practices that minimize water quality impairments from agricultural non-point source pollution (Dosskey 2001, Schultz et al. 2004). The sediment attenuating capacities of riparian buffers have been noted for nearly three decades now (Young and Onstad 1976, Lowrance et al. 1986, Daniels 1996, Schoonover et al. 2006). Although considerable time and financial resources have been applied to the development and implementation of buffers, very little research has addressed the long-term performance of these systems. Field runoff in the form of sheet flow has been identified as an underlying assumption in riparian buffer design and a necessary component in the long-term performance of buffer strips (Dillaha et al. 1989, Dosskey 2001). The development of concentrated flow paths within riparian buffers threatens to weaken buffer performance by reducing the amount of field runoff entering the buffer as sheet flow. This study will address the issues behind development of concentrate flow paths through riparian buffer strips and look at the long term impacts of concentrated flow. In addition, riparian buffer strips will be accessed for sediment attenuating capacity as it relates to the vegetative composition of the buffer and the in field tillage practice.
Particle Size Analysis of Eroded Material from Left Fork of Clover Run, West Virginia
Joshua Stedman
A 9-year paired watershed study was conducted in Tucker County, West Virginia (1999 – 2007) on the western edge of the Allegheny Mountain Range to analyze the distribution of sediment eroded following forest harvesting and road building. The watersheds are tributaries of the river Left Fork of Clover Run and are managed by Cheat Ranger District of the Monongahela National Forest. The watersheds consist of a treatment and an associated reference watershed. The treatment watershed underwent three phases of development. The first phase (i.e., pre-treatment) began in the fall of 1999 and lasted through 2001, and no road construction or harvesting occurred. During the second phase construction of a haul road through the watershed occurred between July 2002 and October 2003. Timber harvest was preformed during the third phase and lasted from September 2003 to October 2006. The reference watershed remained undisturbed for the entirety of the study. A silt fence was constructed along both sides of the entire stream reach draining the watershed to collect the material from the adjacent hill slopes. Samples were processed to separate the mineral and organic components. Mineral material was then separated in to six different size classes using sieve sizes of 4-mm, 2-mm, 1-mm, 125-μm, and 63-μm. Results will be presented comparing the cumulative distribution of the particle sizes for two watersheds on a temporal scale using combined data from the reference watershed and data from phase one from the treatment watershed as a baseline for eroded material. More specifically, data will analyzed to compare road construction and harvesting impacts, along with identifying the main contributor responsible for the greatest portion of fine sediment (<63 μm) reaching the stream bank.
Factors controlling erosion and sediment delivery on an Appalachian gas pipeline
Dan Holz
We will investigate the factors controlling erosion and sediment delivery on a pipeline in the Monongahela National Forest near Parsons, West Virginia. Data collection will begin following pipeline construction in the summer of 2007 and continue until the end of the growing season. This project will have two separate experiments; the first will compare the effects of buffer width, ground cover type, and slope on sediment delivery from a newly installed roadside gas pipeline, and the second will compare the relative importance of slope, aspect, and vegetation type on erosion rates on a cross country gas pipeline. In both studies sediment delivery / erosion rates will be quantified by using silt fences installed on the down slope border of the study plots. Sediment will be collected routinely and summed for the study period to determine total delivery / erosion rates. For the cross country pipeline, vegetation will be the regional standard Kentucky fescue, and a mix of native grasses. Comparisons of vegetative cover vs. erosion rates will be made through analysis of weekly photographs. This information will help determine if a threshold percent vegetative cover level exists for erosion, and how long each vegetation type takes to achieve that level. This study will provide useful information to managers and policy makers regarding erosion and sediment delivery rates on pipeline construction projects. By focusing resources and efforts on the key factors driving erosion and sediment delivery rates, the restoration process will become more effective and efficient.
Nitrogen Dynamics Associated with Autumn-olive Stands at Field and Watershed Scales
Christine Goldstein
Autumn-olive (Elaeagnus umbellata Thunb.) is a nitrogen (N) fixing invasive, exotic shrub that has become naturalized in the eastern United States. The fixed nitrogen could potentially contribute to the non-point source pollution of ground water and surface waters, and ultimately contribute to the eutrophication and subsequent hypoxia of downstream water bodies such as the Gulf of Mexico. Our study objective was to assess the soil nitrogen dynamics and nitrogen leaching in autumn-olive stands at field and watershed scales. To achieve this objective we 1.) examined whether soil net nitrogen mineralization, net nitrification and net ammonification rates and soil water and groundwater nitrogen (nitrate and ammonium) concentrations were greater under autumn-olive stands compared to open field conditions; 2.) determined whether stream nitrate and ammonium concentrations were related to the percent cover of autumn-olive in headwater forested watersheds.
Plots were established at three riparian sites in southern Illinois in both autumn-olive and open field areas. In-situ measurements of soil net N mineralization, net nitrification, and net ammonification were made at each of the three riparian sites. To sample soil water, six tension lysimeters were installed in each vegetation type at the three riparian sites. Soil water samples were collected at least monthly from February 2004 to present and analyzed for dissolved nitrate-N, ammonium-N, pH, and specific conductivity in the Department of Forestry’s Water Quality Research Laboratory. In addition, twelve groundwater wells were installed in January 2006 at the three riparian sites. Groundwater was sampled every two weeks from April 2006 to present and analyzed for dissolved nitrate-N, ammonium-N, pH, and specific conductivity. Watershed sites were chosen in the Indian Creek Watershed in southern Illinois. Twelve ephemeral streams were sampled for dissolved nitrate-N, ammonium-N, pH, and specific conductivity following significant (>1.5 cm) precipitation events. The twelve watersheds were surveyed in summer 2006 to determine percent cover of autumn-olive in each watershed.
Net N mineralization and net nitrification rates were significantly greater (p=0.0029 and p=0.0027) in autumn-olive plots compared to nearby open field plots. Soil water nitrate-N concentrations were significantly greater (p<0.0001) under riparian autumn-olive plots (1.89 ± 0.25 mg/L) compared to nearby open field plots (0.034 ± 0.008 mg/L). However, soil water ammonium-N concentrations were similar (p=0.7405) between autumn-olive and open field plots. Results indicate that ammonium fixed by autumn-olive may be rapidly converted to nitrate and leached via soil water. Groundwater nitrate-N concentrations were significantly greater (p<0.0001) under autumn-olive plots (0.049 ± 0.011) compared with open field plots (0.007 ± 0.003). Groundwater ammonium-N concentrations were also significantly greater (p=0.0025) between autumn-olive (0.162 ± 0.009) and open field plots (0.103 ± 0.006). Percent autumn-olive cover in a watershed explained 68% of the variation in stream nitrate-N concentrations (p=0.0010), however stream ammonium-N concentrations were not correlated with percent cover of autumn-olive (p=0.3005). Study results indicate that autumn-olive may be converting riparian areas from net nitrogen sinks to net nitrogen sources, resulting in greater stream nitrate-N levels.
Community Stakeholders’ Attitudes towards Ecosystem Restoration Goals and Programs in Southern Illinois’ Cache River Wetlands
Christopher Bridges
Many natural resource restoration projects throughout North American urban-rural interfaces have set the stage for large scale ecological change. These projects also have the potential to effect change within social systems. While researchers have given the ecological aspects of restoration intense scrutiny, less is known about its social implications. This study investigates the knowledge, attitudes and behavioral intentions of community members living in southern Illinois, where traditional land use patterns have threatened significant wetland ecosystems. The Cache River Wetlands (CRW) restoration project is spearheaded by a Joint Venture Partnership (JVP) between the U.S. Fish and Wildlife Service, Illinois Department of Natural Resources, The Nature Conservancy and Ducks Unlimited. JVP goals are to restore 60,000 acres of forests and wetlands; specifically to reconnect the Cache River, reduce sedimentation, and restore wildlife habitat. Community members’ perceptions of the project and how its goals and programs affect their lives and livelihoods are unknown. Furthermore, guidance in how to best engage local community members is needed. Personal interviews were conducted with 25 diverse community representatives. Interview questions explored participants’ awareness of the JVP, attitudes toward wetland restoration, and potential involvement in future programs. Research findings indicate a lack of awareness of ecosystem restoration, particularly the need to better communicate local benefits of restoration. Also, residents perceived regional economic depression and associated time constraints as limiting community involvement in Cache River Wetlands restoration. Recommendations are presented for building community support and integrating local stakeholder values into similar restoration projects within the urban-rural interface.
Completed Thesis Projects: (Click student name for pdf. of abstract)
Christine Goldstein, 2007. Nitrogen Dynamics Associated with Autumn-Olive Stands at Field and Watershed Scales.
Justin Fenton, 2007. Quantifying trail erosion and sedimentation associated with equestrian trail use in the Lusk Creek Wilderness Area
Kevin C. Bold, 2007. Erosion control practices in managed forested watersheds: vegetation establishment and broad-based dips
Xizhen Du, 2006. Impact of Channelization and Dam Construction on Kaskaskia River Morphology
Mike Bill, 2005. Channel Morphology and Substrate Responses to High Flows and Road Construction in Forested Mid-Appalachian Watersheds
Jennie Church, 2004. Subsurface nitrogen dynamics in riparian autumn-olive (Elaeagnus umbellata Thunb.) stands in southern Illinois
Christopher Blattel, 2003. Groundwater Nitrogen and Phosphate Attenuation by Giant Cane and Forest Riparian Buffers in the Cache River Watershed
Jon O'Brien, 2002. Factors affecting denitrification in a southern Illinois stream
Jeremy Webber, 2002. Effect of Riparian Forest Cover on Stream Water Quality in Headwater Agricultural Watersheds in Southern Illinois
Jon Schoonover, 2001. Attenuation of Nutrients and Sediment in Agricultural Surface and Subsurface Runoff by Giant Cane and Forest Riparian Buffer Zones
Peer Reviewed Publications:
Goldstein, C.L. and K.W.J. Williard. Soil water nitrogen leaching in riparian autumn-olive stands in southern Illinois. McNair Scholars Journal. In Press.
Schoonover, J.E., K.W.J. Williard, J.J. Zaczek, J.C. Mangun, and A.D. Carver. 2006. Agricultural Sediment Reduction by Giant Cane and Forest Riparian Buffers. Water, Air, and Soil Pollution. 169 (1-4):303-315.
Edwards, P.J. and K.W.J. Williard. 2006. Declines in soil-water nitrate in nitrogen-saturated watersheds. Canadian Journal of Forest Research 36:1931-1942.
Baer, S.G., J.M. Church, K.W.J. Williard, and J.W. Groninger. 2006. Changes in intrasystem N cycling from N2-fixing shrub encroachment in grassland: multiple positive feedbacks. Agriculture, Ecosystems, and Environment 115:174-182.
O’Brien, J.M. and K.W.J. Williard. 2006. Potential denitrification rates in an agricultural stream in southern Illinois. Journal of Freshwater Ecology 21(1):157-162.
Edwards, P.J., K.W.J. Williard, F. Wood, and W.E. Sharpe. 2006. Soil water and stream water chemical responses. Chapter 4. In: Adams, M.B., D.R. DeWalle, and J.L. Hom, eds. The Fernow Watershed Acidification Study. Springer. Dordrecht, The Netherlands.
Adams, M.B., D.R. DeWalle, W.T. Peterjohn, F.S. Gilliam, W.E. Sharpe, and K.W.J. Williard. 2006. Soil chemical response to experimental acidification treatments. Chapter 3. In: Adams, M.B., D.R. DeWalle, and J.L. Hom, eds. The Fernow Watershed Acidification Study. Springer. Dordrecht, The Netherlands.
Stone, M.L., M.R. Whiles, J.A. Webber, K.W.J. Williard, and J.D. Reeve. 2005. Macroinvertebrate communities in agriculturally impacted southern Illinois streams: patterns with riparian vegetation, water quality, and in-stream habitat quality. Journal of Environmental Quality 34(3):907-917.
Blattel, C.R. K.W.J. Williard, S.G. Baer, J.J. Zaczek. 2005. Abatement of ground water phosphate in giant cane and forest riparian buffers. Journal of the American Water Resources Association 39(2):301-307.
Williard, K.W.J., D.R. DeWalle, and P.J. Edwards. 2005. Influence of bedrock geology and tree species composition on stream nitrate concentrations in mid-Appalachian forested watersheds. Water, Air, and Soil Pollution 160:55-76.
Edwards, P.J., K.W.J. Williard, and J.N. Kochenderfer. 2004. Sampling considerations for establishment of baseline loadings from forested watersheds for TMDL application. Environmental Monitoring & Assessment 98:201-223.
Carver, A.D., S.D. Danskin, J.J. Zaczek, J.C. Mangun, and K.W.J. Williard. 2004. A GIS methodology for generating riparian tree planting recommendations. Northern Journal of Applied Forestry 21(2):100-106.
Schoonover, J.E., K.W.J. Williard, J.J. Zaczek, J.C. Mangun, and A.D. Carver. 2004. Nutrient attenuation in agricultural surface runoff by riparian buffer zones in southern Illinois, USA. Agroforestry Systems. 64: 169-180.
Schoonover, J.E., K.W.J. Williard. 2003. Groundwater nitrate reduction in giant cane and forest riparian zones. Journal of the American Water Resources Association. 39(2):347-354.
Williard, K.W.J., D.R. DeWalle, P.J. Edwards, and W.E. Sharpe. 2001. 18O isotopic separation of stream nitrate sources in mid-Appalachian forested watersheds. Journal of Hydrology 252(1-4):174-188.
Williard, K.W.J., D.R. DeWalle, P.J. Edwards, and R.R. Schnabel. 1997. Indicators of nitrate export from forested watersheds of the mid-Appalachians, United States of America. Global Biogeochemical Cycles 11(4):649-656.
Other Publications:
Mangun, J.C., M.D. Gaskins, A.D. Carver, K.W.J. Williard and J.J. Zaczek. A multi-criteria GIS analysis for ranking potential restoration areas in the fragmented Kaskaskia River watershed bottomland hardwood forest. In: Proceedings, 15th Central Hardwood Forest Conference. Feb. 27 - March 1, 2006; Knoxville, TN. Gen. Tech. Rep. NE-xxx. Newton Square, PA: USDA Forest Service, Northeastern Research Station. In Press.
Williard, K.W.J., D.R DeWalle, P.J. Edwards, and P.J. Sharpe. 2004. Impacts of historic fire, stand age, and nitrogen saturation status on soil nitrogen cycling in mid-Appalachian forested watersheds. In: Yaussy, D.A.; D.M. Hix; R.P. Long; and P.C. Goebel, eds. Proceedings, 14th Central Hardwood Forest Conference; March 16-19, 2004; Wooster, OH. Gen. Tech. Rep. NE-316. Newtown Square, PA: USDA Forest Service, Northeastern Research Station: 224-231.
Church, J.M., K.W.J. Williard, S.G. Baer, J.W. Groninger, and J.J. Zaczek. 2004. Nitrogen leaching below riparian autumn olive stands in the dormant season. In: Yaussy, D.A.; D.M. Hix; R.P. Long; and P.C. Goebel, eds. Proceedings, 14th Central Hardwood Forest Conference; March 16-19, 2004; Wooster, OH. Gen. Tech. Rep. NE-316. Newtown Square, PA: USDA Forest Service, Northeastern Research Station: 211-216.
Blattel, C.R., K.W.J. Williard, and S.G. Baer. 2003. Groundwater phosphate attenuation by giant cane and forest riparian buffers. In: J.D. Williams and D. Kolpin, eds. AWRA’s 2003 Spring Specialty Conference Proceedings Agricultural Hydrology and Water Quality. May 12-14, 2003, Kansas City, MO. American Water Resources Association, Middleburg, VA. TPS-03-1. CD-ROM. p.1-4.
Williard, K.W.J., D.R. DeWalle, and P.J. Edwards. 2003. Assessing the extent of nitrogen saturation in northern West Virginia forested watersheds: A survey of stream nitrate concentrations. In: Van Sambeek, J.W.; J.O. Dawson; F. Ponder, Jr.; E.F. Loewenstein; and J.S. Fralish, eds. Proceedings, 13th Central Hardwood Forest Conference; April 1-3, 2002; Urbana, IL. Gen. Tech. Rep. NC-234. St. Paul, MN: USDA Forest Service, North Central Research Station: 121-129.
Schoonover, J.E., K.W.J. Williard, J.J. Zaczek, J.C. Mangun, and A.D. Carver. 2003. Soil water nitrate concentrations in giant cane and forest riparian buffer zones. In: Van Sambeek, J.W.; J.O. Dawson; F. Ponder, Jr.; E.F. Loewenstein; and J.S. Fralish, eds. Proceedings, 13th Central Hardwood Forest Conference; April 1-3, 2002; Urbana, IL. Gen. Tech. Rep. NC-234. St. Paul, MN: USDA Forest Service, North Central Research Station: 206-210.
Webber, J.A., K.W.J. Williard, M.R. Whiles, M.L. Stone, J.J. Zaczek, and K.D. Davie. 2003. Watershed scale assessment of the impact of forested riparian zones on stream water quality. In: Van Sambeek, J.W.; J.O. Dawson; F. Ponder, Jr.; E.F. Loewenstein; and J.S. Fralish, eds. Proceedings, 13th Central Hardwood Forest Conference; April 1-3, 2002; Urbana, IL. Gen. Tech. Rep. NC-234. St. Paul, MN: USDA Forest Service, North Central Research Station: 114-120.
Zaczek, J.J., A.D. Carver, K.W.J. Williard, J.K. Buchheit, J.E. Preece, and J.C. Mangun. 2003. Sap sugar parameters of silver maple provenances and clones grown on upland and bottomland sites. In: Van Sambeek, J.W.; J.O. Dawson; F. Ponder, Jr.; E.F. Loewenstein; and J.S. Fralish, eds. Proceedings, 13th Central Hardwood Forest Conference; April 1-3, 2002; Urbana, IL. Gen. Tech. Rep. NC-234. St. Paul, MN: USDA Forest Service, North Central Research Station: 496-501.
Romano, S.P., J.J. Zaczek, K.W.J. Williard, S.G. Baer, A.D. Carver, and J.C. Mangun. 2003. Riparian forest communities of the lower Kaskaskia River bottoms. In: Van Sambeek, J.W.; J.O. Dawson; F. Ponder, Jr.; E.F. Loewenstein; and J.S. Fralish, eds. Proceedings, 13th Central Hardwood Forest Conference; April 1-3, 2002; Urbana, IL. Gen. Tech. Rep. NC-234. St. Paul, MN: USDA Forest Service, North Central Research Station: 159-166.
Schoonover, J.E., K.W.J. Williard, J.J. Zaczek, J.C. Mangun, and A.D. Carver. 2003. Soil water nitrate concentrations in giant cane and forest riparian buffer zones. In: Van Sambeek, J.W.; J.O. Dawson; F. Ponder, Jr.; E.F. Loewenstein; and J.S. Fralish, eds. Proceedings, 13th Central Hardwood Forest Conference; April 1-3, 2002; Urbana, IL. Gen. Tech. Rep. NC-234. St. Paul, MN: USDA Forest Service, North Central Research Station: 206-210.
Edwards, P.J., K.W.J. Williard, D. Duffield, and B. Edgerton. 2000. Spawning gravel fine sediment levels between seasons and land type associations. In: P.J. Wigington, Jr. and R.L. Beschta, eds. Proceedings of the AWRA International Conference on Riparian Ecology and Management in Multi-Land Use Watersheds. American Water Resources Association, Middleburg, VA. p. 203 – 208.
Williard, K.W.J., D.R. DeWalle, P.J. Sharpe, P.J. Edwards, and M.B. Adams. 1999. Spatial variations in stream nitrate concentrations in a region exhibiting symptoms of nitrogen saturation. In: W.E. Sharpe and J.R. Drohan, eds. The Effects of Acidic Deposition on Aquatic Ecosystems in Pennsylvania. Proceedings of the 1998 PA Acidic Deposition Conference, Vol. II. Environmental Resources Research Institute, University Park, PA. p. 23-30.
