Number  54                    July 1992              ISSN 1062-9149

Betty Hermsmeyer
Agricultural Stabilization and Conservation Service

Project Synopsis

The Long Pine Creek RCWP Project is located in north central Nebraska on the northeastern edge of the Nebraska Sandhills, the only grass-covered sand dune area in the world. The Sandhills rest upon the Ogallala Aquifer, a 200-mile wide corridor of underground water that extends south through Kansas and Oklahoma into Texas.

The watershed is drained by Long Pine Creek, the longest self-sustaining trout stream in the state. The creek and its tributaries provide over 79 miles of winding stream in a rugged setting. Its natural beauty and recreational and wildlife importance makes the area one of Nebraska's natural treasures.

The Long Pine Creek watershed encompasses 325,000 acres of rolling plains and flat tablelands with deep cut canyons and draws. The area is sparsely populated and supports ranching and framing, with no major industry. The Ainsworth Irrigation District brought irrigation to 35,000 acres in the mid 1960s. Farmers focus mainly on irrigated corn production with some production of popcorn, soybeans, and alfalfa.

In the late 1970s, the watershed was identified as having severe ground and surface water problems. The nitrate-nitrogen content in municipal and domestic water supplies was beginning to exceed maximum contamination standards. Pesticide contamination of ground and surface water was becoming apparent. Sediment from agricultural runoff and erosion was filling creeks and streams and seriously degrading trout habitat. The bacterial content in surface waters was posing a health hazard to humans and wildlife.

Project Objectives and Goals

Project objectives and goals were to reduce: stream bank erosion, the delivery of sediment from agricultural lands to Long Pine Creek, the deep percolation of irrigation water contaminated with pesticides and fertilizers, excess irrigation water runoff, and nonpoint source agricultural pollution from feedlots. The project's land treatment implementation goal was to treat 75% of the critical area with appropriate best management practices (BMPs).

Project Administration and Coordination

The RCWP project emphasized interagency cooperation. The program was administered through the Agricultural Stabilization and Conservation Service (ASCS). A Local Coordinating Committee (LCC) consisting of members of 15 agencies and groups was responsible for implementing the project.

Best Management Practices Implemented

Fifteen BMPs were selected to address nonpoint source pollution problems on 60,242 acres determined as critical and targeted for treatment.

Selected Findings and Recommendations:

• Initial objectives and goals for implementation cannot be made until specific information and data are studies. For example, the critical area needs to be clearly defined and the water quality problems and problem areas fully understood before realistic implementation goals can be set.
  

• Economic evaluation objectives and goals should be incorporated into the project.
  

• Federal farm programs that regulate feed grain production can affect land use patterns and water resource management throughout the project period. These effects will have to be taken into consideration when adjusting objectives and goals.
  

• Knowledge and experience gained by technicians working with RCWP can be applied to other water quality projects.
  

• There were insufficient ASCS and Soil Conservation Service (SCS) personnel devoted solely to the RCWP at the beginning of the project.
  

• A project coordinator is of utmost importance in a project of the size and length of the RCWP projects. Throughout the decade of the RCWP activity, there were many years when the efforts of all agencies were drawn toward other programs which were assigned immediate priority. A project coordinator is necessary to move the project ahead during these difficult times, to maintain the continuity of the program, and to keep the program focused on goals and priorities.
  

• The project would have benefited from better communication among local, state, and national level agencies.

• The State Coordinating Committee (SCC) and the LCC need to interact to a greater degree for mutual understanding. The SCC should be involved in some of the hands-on negotiations and problem solving at the local level.

• At the beginning of the project, the members of the LCC did not have a good understanding of nonpoint source (NPS) pollution. The LCC would have benefited from attending an orientation seminar where NPS pollution was explained in detail and where a format for organization, critical area selection, and prioritization were presented.

• When economic advantages of BMPs are emphasized, practices are widely adopted.
  

• State agencies, such as the Nebraska Game and Parks Commission, the Middle Niobrara Natural Resource District, the North Central Nebraska Resource Conservation District, and the Nebraska Department of Environmental Control were brought into the project and contributed greatly to its success.

• A log needs to be established to record technical and economic data (by individual practice) throughout the life of the project.

• Each RCWP project is unique and provides each state with a valuable resource. Each project has accumulated a vast amount of knowledge about BMPs and their relationships to point and NPS pollution. RCWP watersheds should become educational centers for technical personnel in all agencies.
  

• Information and education is most effective when responsibility is given to one agency.
  

• Field demonstrations are a powerful tool for communication with producers.
  

• Funds need to be allocated specifically for information and education activities.
  

• Monitoring programs should be holistic. Consideration should be given to water quality, habitat quality, biotic integrity, land treatment, and land use.

• It is critically important that a monitoring plan be prepared that clearly defines how the monitoring program will be implemented and how the effectiveness of the project will be evaluated. The plan should include: 1) clearly defined monitoring goals; 2) a project description that identifies the monitoring network design and rationale , the variables to be monitored, and the frequency and method of collection; 3) fiscal information related to the monitoring program; 4) a schedule of tasks and products; 5) personnel responsibilities; 6) data management provisions; 7) reporting requirements; and 8) appropriate quality assurance/quality control provisions.

• Monitoring should allow for water quality assessment by hydrologic unit. A "paired watershed" or "upstream-downstream" monitoring design should be used whenever possible.

• Direct measures of beneficial use support (such as aquatic biota occurrence, embryo survival) should be used whenever possible. The use of such information may require utilization of reference sites.
  

• Variability in data caused by flow or seasonality are important in assessing water quality and must be accounted for to the greatest degree possible.

• Extensive monitoring using a "laundry list" approach should be avoided. Relationships between NPS pollutants and loadings and their impacts on beneficial uses should be discerned. These relationships should be used to identify critical variables, including covariates, for monitoring.
  

• Water quality monitoring and evaluation results should be used by resource managers as much as possible to identify critical areas and to select and prioritize BMPs.
  

• Fertilizer and pesticide management practices implemented through the RCWP project were widely adopted outside the critical area. As a result, significant reductions in fertilizer and pesticide use have been achieved.

• The inability to cost share feedlots (considered point sources) had a negative effect on the project.
  

• Cedar revetments were one of the most innovative and successful practices implemented through the RCWP project. Constructed for streambank stabilization, they provided a variety of habitat benefits to trout and other aquatic life.

• Emphasis on BMP systems (practices that work together to achieve specific goals) better address overall problems than emphasis on installment of individual practices.

• Time-consuming design and approval procedures for practices under BMP 2 (animal waste management system) delayed implementation.

• The project would have benefited from a greater acceptance of experimental practices as part of the project. Even if these practices do not contribute to the achievement of project goals, a great deal can be learned from the process of experimenting with BMP modification and development.
  

• Land use and land treatment within the project area (both project participants and non-participants) should be tracked in the land treatment data base. Land treatment data tracking should not end with contract expiration if the project is still ongoing.

• BMP effectiveness monitoring is important in that it provides feedback to project participants.
  

For Further Information

Betty Hermsmeyer
ASCS
1292 East Fourth Street, R.R. 2, Ainsworth, NE 69210
Tel: 402-387-2242

Gaston County is a rapidly growing county in the southwestern Piedmont region of North Carolina. As nearby industrial and urban centers expand, public concern for the quality of natural resources has steadily increased. Reports of cleaning solvent (trichloroethylene) in a private well several years ago and degradation of local streams have heightened awareness among county commissioners that environmental quality deserves high priority. The commissioners requested assistance from NCSU natural resources faculty and the Water Quality Group to assess surface water, ground water, and air quality using existing data. A phased program of research and technical assistance has been conducted over the past two years to assist county leaders in addressing the natural resource problems and needs they currently face and will need to manage in the future. Phase 1 of the project was reported in issue 46 of NWQEP NOTES (September 1990). The following article describes work conducted by the NCSU Water Quality Group for Phase 2 of the Gaston County project. Phase 2 also included a well water survey, a ground water analysis, and education program planning and policy development, each conducted by NCSU faculty and staff.

Daniel E. Line
NCSU Water Quality Group

As an extension of the Gaston County Water Quality Data Base Development and Assessment Study, the NCSU Water Quality Group conducted a surface water quality modeling study of Gaston County's Long Creek watershed. Models used ranged in complexity from simple pollutant export coefficient types to sophisticated continuous and single-event models, such as the Agricultural Non-Point-Source Pollution (AGNPS) (YOUNG et al., 1989) and Simulator for Water Resources in Rural Basins-Water Quality (SWRRBWQ) (Arnold et al., 1990) models.

The Long Creek watershed (about 26,500 acres) encompasses a mixture of urban and agricultural land uses. Five dairies, ranging in size from 80 to 400 cows, are located in the watershed. Three urban drainage areas of between 800 and 1,700 acres, containing a variety of business, residential, and industrial land uses, lie within the watershed.

Critical pollutant source areas such as dairy feedlots and intensively cultivated fields were identified from AGNPS output based on the availability and mobility of sediment, nitrogen, and phosphorus. Critical areas (62 acres) were then prioritized according to the level of pollutant loading to Long Creek from the larger drainage area in which they were located. In this way, subwatersheds contributing the greatest pollutant loadings were targeted and critical pollutant source areas within subwatersheds were also targeted. This targeting will help the county focus on reducing the most significant sources of pollutants to Long Creek.

The AGNPS model was also used to estimate the hydrologic effects of possible business and industrial expansion in the watershed. The model indicated significant increases in peak runoff rates and pollutant loadings to Long Creek, particularly for the relatively undeveloped headwater section of the watershed.

The SWRRBWQ model was calibrated from streamflow data and then used to estimate the long-term (40-year) hydrology of the watershed. Model results indicated that the implementation of BMPs to improve infiltration would substantially decrease nitrogen transport in the watershed. Export coefficient, SWRRBWQ, and point source pollution estimates were then used to compile nutrient budgets for the overall Long Creek watershed.

The Program for Predicting Polluting Particle Passage through Pits, Puddles, and Ponds (P8) (Palmstrom and Walker, 1990) model was used to estimate pollutant loadings from the three urban subwatersheds. The model was also used to calculate the reduction in pollutant loading associated with the construction of a 10-acre wet detention pond on the largest subwatershed. Results indicated that urban areas could be significant sources of pollutants to Long Creek and that a detention pond would reduce pollutant loadings of suspended solids, nutrients, and metals by 23 to 68%.

Surface water modeling results are being used to help identify locations and select appropriate designs for water quality monitoring in the watershed. Also, modeling results are being evaluated for use in determining a total maximum daily load (TMDL) for Long Creek (see the article on Guidance for Water-Quality Based Decisions in the INFORMATION section of this issue of NWQEP NOTES for a description of TMDLs)

The 135-page report on all four components of the Phase 2 Gaston County Project, entitled Natural Resource Quality in Gaston County, Phase 2: Implementation of Natural Resource Education and Policy Development Programs, is available from the NCSU Water Quality Group at a cost of $12 (WQ- 72). A separate appendix to the report (WQ-73), containing publications related to the project, is available at a cost of $9.

References

Arnold, J.G., J.R. Williams, A.D. Nicks, and N.B. Sammons. 1990. SWRRBWQ: A Basin Scale Simulation Model for Soil and Water Resources Management. Texas A & M University Press, College Station, TX. 16p.

Palmstrom, N. and W.W. Walker. 1990. P8 Urban Catchment Model: User's Manual. IEP, Inc., Concord, MA. 303p.

Young, R.A., C.A. Onstad, D.D. Bosch, and W.P. Anderson. 1987. AGNPS, Agricultural Non-Point- Source Pollution Modeling: A Watershed Analysis Tool. Cons. Res. Rep. 35, USDA Agricultural Research Service, Washington, DC. 77p.

The following article completes a three-part article on nonpoint source (NPS) modeling for evaluation of best management practice (BMP) effectiveness (see NWQEP NOTES No. 52, March 1992) and NWQEP NOTES No. 53, May 1992) for the first two parts of the article). A variety of models and geographic information systems (GIS) are being used for a wide range of NPS applications. Some of these applications will be discussed in this Technical Notes series, with emphasis on specific NPS projects or programs that have used models and/or GIS. Readers interested in contributing to the series are encouraged to contact Judith Gale, NWQEP NOTES editor.

Theo A. Dillaha, Department of Agricultural Engineering, Virginia Polytechnic Institute and Scientific University
Judith A. Gale, NCSU Water Quality Group

Brief Descriptions of Selected Nonpoint Source (NPS) Models

Runoff from the land segments drains to channel reaches with uniform hydrologic properties and to larger receiving waters if they exist. It is difficult to include many land segments in the model because increasing their numbers greatly increases calibration and input data requirements. HSPF is a large model that requires several years of historical hydrologic records for calibration, extensive data bases, and large computer resources. A publication is available to help in selecting model parameters for simulating agricultural BMPs (Donigian et al., 1983). The calibration required to run the model and its lumped parameter approach makes it difficult to evaluate changing watershed conditions caused by BMP implementation. The model is calibrated to existing conditions and modifying parameters for future conditions is difficult (Novotny and Chesters, 1981). HSPF has received much less independent verification than other NPS models and should be used with caution. Formal training is recommended before attempting to use HSPF (Crowder, 1987).

NONPOINT SOURCE POLLUTION LOADING (NPS) MODEL (Donigian and Crawford, 1976) is an earlier version of the ARM model developed to estimate nutrient losses in surface runoff from urban and agricultural areas. Like ARM and HSPF, NPS requires historical hydrologic records for calibration. In addition to nutrients, the model simulates runoff, sediment, water temperature, and dissolved oxygen. Data requirements are not as extensive as those of ARM, and the model can simulate runoff from up to five conceptual land segments in a single run. The model was reported to adequately simulate total nitrogen and phosphorus loadings and concentrations from agricultural watersheds where nutrients were primarily sediment-bound (Donigian and Crawford, 1977). Where runoff is low and pollutants are primarily in dissolved forms, the model does not predict well because it does not consider dissolved pollutant transport. All pollutant losses other than sediment are estimated by multiplying sediment losses by a potency factor. Thus, the model would probably be poor in evaluating BMPs like conservation tillage that greatly reduce sediment yields but often increase pollutant concentrations. Because of these shortcomings, the model has limited value for evaluating BMPs (Crowder, 1987). A modified version of NPS was used as the NPS pollution loading sub-model in the Chesapeake Bay Program's Chesapeake Basin Model (Hartigan et al., 1983). The model received a limited amount of calibration on 11 test watersheds within the basin. Few details on the calibration and testing of the model have been reported, and it is unclear whether the model was appropriate or well-calibrated.

STORAGE, TREATMENT, AND OVERFLOW MODEL (STORM) (U.S. Army Corps of Engineers, 1975) is either an event-based or continuous simulation model developed for urban stormwater management. The program is intended for simulating the quantity and quality of runoff from small, primarily urban, watersheds, but rural areas can also be simulated. Modeled parameters include total and volatile suspended solids, biochemical oxygen demand, total nitrogen, and orthophosphorus. As with NPS, the water quality parameters are assumed to be related to suspended solids. The model does not route surface runoff, and because of the questionable use of the rational method for estimating runoff, runoff volumes can be highly inaccurate even with calibration (Novotny and Chesters, 1981). Soil loss from pervious areas is estimated using the USLE and user-supplied delivery ratios. Wash-off from impervious areas is estimated by using a form of the Sartor wash-off equation (Sartor et al., 1974). The model considers storage and treatment of stormwater and can consider urban BMPs such as sediment detention basins and ponds (using a trap efficiency parameter) and street sweeping.

STORM WATER MANAGEMENT MODEL (SWMM) (Huber et al., 1983) is the most sophisticated and widely used model developed for urban stormwater management. SWMM is a continuous simulation, watershed-scale (5 to 2000 ha) model that simulates runoff quantity and quality from pervious and impervious areas, erosion, scour, sediment transport, dry weather flow, and pollutant routing in sewers, stormwater storage and treatment, and receiving water quality. SWMM divides a watershed into small homogeneous sub-catchments (a maximum of 200) and routes runoff from these catchments to the drainage system. SWMM simulates wash-off from impervious surfaces like STORM. Loadings of pollutants other than sediment are generated from sediment yields using user-supplied potency factors. The program is large and requires extensive input data, but calibration is not required. A comprehensive user's manual is available (Huber et al., 1983) and U. S. EPA supports regular user's conferences and workshops on the model. The model's use for simulating NPS pollution processes and problems was reported to be limited (Novotny and Chesters, 1981).

WATER EROSION PREDICTION PROJECT MODEL (WEPP) (Gilley et al., 1988) is one of the most significant developments that will affect NPS pollution control efforts in the future. This model is being developed by the U. S. Department of Agriculture to replace the Universal Soil Loss Equation (USLE). The USLE was developed over 20 years ago and has been an integral part of virtually all NPS and erosion control planning efforts. The WEPP model is intended to correct some of the deficiencies of the USLE, such as poor estimation of erosion with contouring and steep slopes. In addition, WEPP will be able to predict soil losses for individual storms using readily available input data. WEPP will be computer based and will contain soil, crop, and weather data bases to facilitate model use. The model will simulate the effects of climate, soils, topography, and cropping-management conditions on erosion, deposition, and sediment transport. The model will consist of three basic versions: 1) representative overland flow profile, 2) watershed, and 3) grid. The initial version of the WEPP technology was delivered during the summer of 1989 and the final model version intended for public use is expected to be available in 1994.

Nonpoint Source Modeling Research Needs

Research needed to improve the usefulness of models for NPS pollution control include:

• Improved understanding of pollutant transport processes between fields and streams. Particular emphasis should be placed on the role of filter strips and riparian zones.
  

• Development of satisfactory equations for describing sediment transport in shallow overland flow. Currently-used equations were developed for channel flow conditions, which differ significantly from shallow overland flow conditions.
  

• Development of a nitrogen accounting model for temperate humid regions to allow better simulations of nitrogen transformations and availability of various nitrogen species.
  

• Development of a VFS (filter strip) design model that considers the effects of concentrated flow and long-term sediment and nutrient accumulation in VFS.
  

• Building comprehensive data bases for model development, testing, and verification. A series of intensively monitored (long-term) watersheds should be established which collect detailed data on weather; land use; cropping; chemical applications; runoff rates, quantity and quality; soil chemistry; and pollutant transport; etc. Without these data, models will continue to be evaluated with inadequate data bases and modeling limitations will be blamed on data limitations rather than limitations of the models.
  

• Concentration of model development efforts for BMP assessment on physically-based, deterministic, distributed parameter models. These models are designed for use without calibration and have significant theoretical advantages over other types of models in evaluating BMP effectiveness.
  

• Development of standard methods to determine whether model predictions fall within a prescribed range of true values. Without this, it is difficult to compare alternative models or determine the adequacy of model predictions.
  

• Improved screening/targeting models to identify potentially critical sources of NPS pollution to improve the cost-effectiveness of NPS pollution control programs. Particular emphasis should be placed on the development of geographic information systems for NPS management.
  

• Improved understanding of the long-term effects of conservation tillage practices, particularly no-till, on ground water quality.
  

• Research into the effectiveness of alternative animal waste containment and treatment facilities on nutrient removal and disinfection.
  

References

Crowder, B.M. 1987. Issues in water quality modeling of agricultural management practices: an economic perspective. In: Proceedings of the Symposium on Monitoring, Modeling, and Mediating Water Quality; 1987 May; Minneapolis, MN. American Water Resources Association; pp. 313-327.

DeCoursey, D.G. 1985. Mathematical models for nonpoint water pollution control. J. Soil Water Conserv. 40(5):408-413.

Donigian, A.S. and N.H. Crawford. 1976. Nonpoint Pollution from the Land Surface. Athens, GA: U.S. Environmental Protection Agency; EPA-600/3-76-083.

Donigian, A.S. and N.H. Crawford. 1977. Simulation of Nutrient Loadings in Surface Runoff with the NPS Model. Athens, GA: U.S. Environmental Protection Agency; EPA-600/3-77-065.

Donigian, A.S., J.L. Baker, and D.A. Haith. 1983. HSPF Parameter Adjustments to Evaluate the Effects of Agricultural Best Management Practices. Athens, GA: U.S. Environmental Protection Agency. EPA- 600/3-83-066.

Gilley, J.E., L.J. Lane, J.M. Laflen, A.D. Nicks, and W.J. Rawls. 1988. USDA-water erosion prediction project: new generation erosion prediction technology. In: Modeling Agricultural, Forest, and Rangeland Hydrology: Proceedings of the 1988 International Symposium; 1988 Dec. 12-13; Chicago, IL. St. Joseph, MI: American Society of Agricultural Engineers; pp. 260-263.

Hartigan, J.P., E. Southerland, H. Bonucelli, A. Canvacas, J. Friedman, T. Quasebarth, K. Roffe, T. Scott, and J. White. 1983. Chesapeake Bay Basin Model Final Report. Annandale, VA. Northern Virginia Planning District Commission.

Huber, W.C., J.P. Heaney, S.J. Nix, R.E. Dickinson, and D.J. Polmann. 1983. Storm Water Management Model User's Manual: version III. Gainesville, FL: Univ. of Florida, Dept. of Environmental Engineering Sciences; p. 505.

Johanson, R.C., J.C. Imhoff, H.H. Davis, J.L. Kittle and A.S. Donigian. 1981. User's Manual for Hydrologic Simulation Program-Fortran (HSPF): Release 7.0. Athens, GA: U.S. Environmental Protection Agency.

Novotny, V. and G. Chesters. 1981. Handbook of Nonpoint Source Pollution: Sources and Management. New York: Van Nostrand Reinhold Co.

Sartor, J.D., G.B. Boyd, and F.J. Agardy. 1974. Water pollution aspects of street surface contaminants. J. Water Poll. Cont. Fed. 46:458-667.

U.S. Army Corps of Engineers. 1975. Urban Storm Water Runoff- STORM. Davis, CA: Hydraulic Engineering Center.

EPA. 1991. Guidance for Water Quality-Based Decisions: The TMDL Process. Assessment and Watershed Protection Division, U.S. Environmental Protection Agency, Washington, DC 20460. EPA 440/4-91-001.

The Environmental Protection Agency's (EPA) Office of Water has published a guidance document intended to explain the programmatic elements and requirements of the Total Maximum Daily Load (TMDL) process established by Section 303 of the Clean Water Act. A TMDL is a tool for implementating state water quality standards and is based on the relationship between pollution sources and in-stream water quality conditions. The TMDL establishes the allowable loadings for a waterbody, thereby providing the basis for states to establish water quality-based controls.

The publication includes chapters on the water quality-based approach to pollution control, development and implementation of the TMDL, and EPA and state responsibilities. Appendices address the relationship to other guidance, supporting programs, screening categories, technical considerations, mathematical model support, general EPA/state agreement outline for development of TMDLs, and causes and sources of pollution.

For copies, contact the Watershed Branch, Assessment and Watershed Protection Division, 401 M Street SW, Washington, DC 20460.

Taggart, J. and B. Bracht. 1991. Handle with Care: Your Guide to Preventing Water Pollution. The Terrene Institute, Washington, DC.

Handle with Care is a primer and guide designed to educate citizens about nonpoint source pollution and roles individuals can play in preventing water pollution. Copies of this attractive 36-page booklet may be obtained from The Terrene Institute, 1000 Connecticut Ave., NW, Suite 802, Washington, DC 20036, Tel: 202-833-8317. The cost is $9.95.