Proceedings of the U.S. Geological Survey (USGS) Sediment Workshop, February 4-7, 1997

SEDIMENT RESEARCH NEEDS AND RELATED SUPPORT FOR PROGRAMS OF THE USDA--NATURAL RESOURCES CONSERVATION SERVICE

GENERAL

The agency's concern with sediment began with soil erosion reduction as a primary focus in the 1930's. Over the years, the agency has collaborated with the USDA--Agricultural Research Service to develop reliable predictive equations for field use to determine the effectiveness of soil erosion control practices and programs (tons of soil saved). Examples range from the lumped parameter Universal Soil Loss Equation (USLE), Wind Erosion Equation (WEQ), the Revised USLE (RUSLE), and the Revised Wind Erosion Equation (RWEQ) to the process simulation model, the Water Erosion Prediction Project (WEPP), and the Wind Erosion Prediction System (WEPS). WEPP simulates sheet and rill erosion, concentrated flow erosion, and sediment transport and deposition along a measured field slope, including the sediment size distribution, which is important to water quality impacts. Depending on the land use, WEPP can also make these estimates for watersheds less than 2,000 acres in drainage area. Dave Schertz, National Agronomist, is the NRCS leader for these models. WEPP and WEPS should be fully operational around 2000.

NRCS currently works with private landowners to protect natural resources. This mission gives equal weight to the reduction of soil erosion rates, as well as reducing the amount and impact of sediment on natural resources.

The NRCS relies heavily on USGS for the water and sediment data that they collect at stream gages.

NRCS is partnering with the ARS in identifying and prioritizing research in many subject matter areas related to the protection of natural resources, including the prediction and control of erosion, stream restoration, and the modeling of the effects of watershed protection actions on water quality and other natural resources. Examples are a variety of field and watershed scale models, including EPIC, SWRRBWQ, ANNAGNPS, MUSLE, HUSLE, HUMUS. Key contacts in this partnering are Lee Herndon, NRCS, Dick Amerman, ARS, and Wil Fontenot, NRCS.

The modeling of water quality effects of resource protection programs, including sediment yield rates, remains high on the list of needs in the agency. Models that are simple, reliable, and do not require users to key-in lavish amounts of data are especially needed. The fact is that models are the only means to route water and sediment and other pollutants on a watershed basis and in a manner which allows planners to determine not only the effects of treatments on dispersed areas over long time periods, but also the treatments needed based on landscape and watershed location and in identifying high priority treatment areas.

SPECIFIC NEEDS

Item #1) Sediment transport component of the Hydrologic Unit Model for the United States (HUMUS) needs to be validated.

• Model results need to be compared with USGS stream gage data and reservoir sedimentation surveys, and the model's sediment transport component revised and improved accordingly.

• Contacts are Jeff Arnold, ARS; Bob Kellogg, Verel Benson, and Tom Iivari, NRCS.

• Survey activity has dropped off severely since the mid-1980's due to perceptions that water and sediment surveys are too costly, take too much time, cannot be repeated easily, are not accurate, and may not be needed.

• Recent advances in remote sensing technology and GPS provide the ability to perform surveys rapidly, more accurately, with less intrusion, and at much reduced costs.

• Watershed land use information is needed as support data for each survey time period, in order to determine the conditions that produced the amount of sediment measured. Such data also translate to effectiveness of watershed protection programs.

• More frequent surveys on a greater number of reservoirs with small drainage areas is needed to determine changes in sediment yields effected by various farm programs administered at the state and federal level.

• Contacts are Jerry Bernard, Tom Iivari, and Lyle Steffen.

• RESIS was developed by ARS and NRCS in support of the Third Resource Conservation Act, for a report to Congress. Reservoir survey data that was in digital format from earlier attempts to create such a data base were put into an INFORMIX relational data base.

• RESIS is currently only accessible on three stand-alone PC's: one at the ARS Blacklands Prairie Research Laboratory in Temple, TX (Dr. Jay Atwood); one at the NRCS National Soil Survey Center, Lincoln, NE (Lyle Steffen); and one at the USGS (with EROS, working on carbon sequestration study). The data base can be queried through SQL on an ad hoc basis. It is not networked, nor accessible to the public.

• RESIS data base lacks current reservoir sedimentation survey data, as noted above. Data base currently includes 6000+ records, with few surveys since about 1985.

• Issues about water resources structure rehabilitation, decommissioning, and changed functions will include environmental consequences of reservoir sediment deposits exposed, eroded, excavated, etc., as a result of implemented plans.

• Sediment toxicity maps or data base are needed to the extent that they can be developed. The EPA started this process on coastal and harbor areas, but needs to be extended inland.

• Standards for the accurate and scientific characterization of sediment quality or toxicity need to be developed.

• Sediment yields appear to remain high in the upper Mississippi River Basin, although farm programs have emphasized erosion controls there over the 11 years between gage analyses done by the USGS and reported in its National Water Report of 1995.

• Some studies on small agricultural watersheds, some with drainage systems installed and some without artificial drainage systems added, would help clarify the conditions that are producing the sediment. What is the contribution of off-the-farm erosion processes such as stream bank erosion to the total yields?

• Ephemeral gully erosion is a significant sources of sediment where this type of erosion occurs and affects the processes of sediment transport off the field.

• Procedure is needed to identify the extent and/or location of ephemeral gullies (recurring concentrated flow erosion in swales or at base of opposing slopes). Present model, EGEM, requires the user to enter the gully length as input.

• Mechanics of ephemeral gully erosion need to be refined.