Riparian Management for Water Quality, the Bear Creek Example: Getting the Message Out

While a considerable body of evidence confirms that exiting vegetated streamside zones can be effective sinks for nonpoint source pollution (Castelle et al. 1994, Osborne and Kovacic 1993, Lowrance 1992, Cooper et al. 1987, Jacobs and Gilliam 1985, Lowrance et al. 1985, 1984, Peterjohn and Correll 1984), little information is available for restored or constructed streamside buffer systems. To demonstrate the benefits of properly functioning riparian zones in the heavily row-cropped midwestern U.S., the Agroecology Issue Team of the Leopold Center for Sustainable Agriculture and the Iowa State Agroforestry Research Team (IStART) are conducting research on the design and establishment of integrated riparian management systems. The purpose of these systems is to restore the essential ecological functions that these riparian areas once provided. Specific objectives of such buffers are to intercept eroding soil and agricultural chemicals from adjacent crop fields, slow flood waters, stabilize streambanks, provide wildlife habitat, and improve the biological integrity of aquatic ecosystems

Improving Soil and Water Quality with Riparian Buffers

The agricultural landscape has four major sources of non-point source (NPS) pollutants. These are: 1) surface and subsurface runoff which carry sediment and agricultural chemicals to streams; 2) eroding streambanks which can contribute more than fifty percent of the sediment load to the stream; 3) field tile drains which contribute the highest concentrations of soluble agricultural chemicals to streams; and 4) livestock grazing of streamside or riparian areas which contribute to bank instability and add animal waste and pathogens to the water. Maintaining or establishing a forested or prairie buffer along streams and rivers provides more than just a beautiful landscape. While a considerable body of evidence confirms that existing vegetated streamside zones can be effective sinks for NPS pollution (Castelle et a!. 1994, Osborne and Kovacic 1993, Lowrance 1992, Cooper eta!. 1987, Jacobs and Gilliam 1985, Lowrance eta!. 1985, 1984, Peterjohn and Correll 1984), little information is available for restored or constructed streamside buffer systems. Designing and establishing the right combination of native trees, shrubs and grasses as buffer strips and integrating them with constructed wetlands, soil bioengineering and rotational grazing can improve water quality

High stage events and stream bank erosion on small grazed pasture stream reaches in the rathbun lake watershed, southern IOWA, USA

Stream bank erosion in agricultural landscapes is a major pathway for non-point source sediment and phosphorus loading of receiving waters. Previous studies have shown direct and indirect effects of land use on stream bank erosion, and identified high erosion rates within riparian pastures. One potential impact of agricultural land-use on stream bank erosion is the alteration of stream stage characteristics, including an increase in frequency of high-stage events over short periods of time (forming flash hydrographs). The objective of this study was to assess the relationship between the number of high stream stages and corresponding stream bank soil erosion. The study was conducted in six grazed pasture stream reaches within the Rathbun Lake Watershed, a reservoir on the Chariton River located within the Southern Iowa Drift Plain. The erosion pin method was utilized to measure the change in stream bank erosion in response to differences in the number of high stream-stage events, which were monitored by pressure transducers. The measured seasonal bank erosion rates were correlated with the different stream stages data to assess their impact on stream bank erosion. Based on the different model assumptions, there were generally strong linear relationships between high stage and bank erosion. Approximately 75% of the variability in stream bank erosion rates was directly linked to the number of high stages/erosive stream flow depths. Conservation practices that reduce these erosion rates will be those that increase soil-water infiltration, reduce the frequency of high stream flow events and increase bank stability through perennial vegetation cover or reducing disturbance within the riparian zone