Wisconsin Buffer Initiative Support by the Non-Point Project
The Non-Point Source Pollution project in the Soils Department at UW-Madison has been providing partial support for activities that are part of the Wisconsin Buffer Initiative (WBI). The WBI was formed in mid 2002 at the request of the Wisconsin Department of Natural Resources (WDNR) Board to develop an adaptive management approach based on sound and applicable science to guide the establishment of policy with respect to using buffers to protect Wisconsin's streams and lakes from non-point source pollution. Leadership and fiscal decisions are the purview of the WBI Executive Committee and technical issues are handled by the WBI Advisory Committee. The WBI Advisory Committee is composed of scientists from UW-Madison and other campuses, agency staff (federal and state), agricultural groups, conservation associations, and environmental organizations. The five subcommittees of the WBI Advisory Committee are as follows:
- Monitoring and Modeling
- Buffer Location
- Buffer Design and Maintenance
- Buffer Performance and Assessment
- Policy Tools and Buffer Adoption
The Non-Point Source Pollution project is primarily involved in the Monitoring
and Modeling activities of the WBI with minor roles in buffer location, design,
maintenance, performance and adoption as they overlap with the Monitoring and
Modeling goals. The purpose of the Monitoring and Modeling subcommittee is to
establish a scientific basis for the use of buffers to reduce the transport of
phosphorus and sediment from agricultural land to streams. A successful project
would provide scientifically based information to support or modify current NRCS
standards for the design and placement of buffers. The following figure provides
an overview of the Monitoring and Modeling activities.
Objectives The overall objective is to create a practical tool for field practitioners to use as a guide for designing effective buffers on typical agricultural landscapes. Specific objectives include the following:
- Establish and maintain field sites and measurement protocols to quantify the loss of sediment and phosphorus from several typical agricultural sites;
- Adapt and validate the Precision Agricultural Landscape Modeling System (PALMS) to generalize the results from the limited number of measurement sites to the diverse landscapes typical of Wisconsin;
- Use the combined results from the model and measurements to calibrate the SNAP+/RUSLE2/P-Index tool for guiding the implementation of buffers in Wisconsin
Measurements include quantities that will be input into the model or application tool as well as quantities that will be output. Model input quantities that will be measured include field characteristics (soil type, topography, location), management factors (cropping patterns, residue, tillage, fertilization or manure application), weather (hourly solar radiation, temperature, humidity, wind speed and precipitation), and buffer characteristics (dimensions, location, slope, plant types, contributing area). Model output quantities that will be measured include the total loss of phosphorus and sediment from the agricultural field with and without the buffer, the buffer efficiency, and the total runoff.
The runoff measurement system consists of a covered collector to capture the
runoff, sediment and P coming from a carefully measured contributing area in the
field, and a divisor system for quantifying the sediment, P and runoff coming
from the field. A weather station also collects critical data.
Two modeling efforts are proposed for this study: 1) A detailed processed-based model to generalize the measurements to more diverse landscapes than can reasonably be accommodated in the monitoring program, and 2) an easy-to-use application tool for practitioners to use in the field to guide buffer location and design.
The Precision Agricultural-Landscape Modeling System (PALMS) is being adapted for use with buffers. PALMS is a processed-based model that currently computes runoff as a function of slope, precipitation intensity, heterogeneous soils, crop type, tillage type and orientation relative to the slope/aspect, residue and fertilization. Recently erosion and phosphorus chemistry routines have been added to PALMS. The influence of buffers on plant growth and yield is calculated in PALMS for both the crop and the buffer vegetation as a function of location in the field.
Data from several field sites will be used to evaluate PALMS. One or more sites then will be used for independent validation in which model output is compared to measurements without adjusting parameters to improve agreement.
The application tool will be SNAP+/RUSLE2/P-Index and is being developed by others. Data from this Monitoring and Modeling activity will be used to evaluate the tool, in addition to output generated from PALMS over diverse scenarios typical of Wisconsin agriculture.
PALMS is a detailed model created from a combination of the Integrated Biosphere
Simulator (IBIS) and a two-dimensional diffusive wave runoff model. IBIS simulates
all the mass and energy exchanges as well as growth that occurs on a single grid
cell in a landscape, and the diffusive wave runoff/sediment model routes the
movement of water over the landscape when it rains or irrigation occurs.
An example of PALMS output for infiltration and erosion is included below for one of the fields at Farm B.
Following are preliminary results from the first year of monitoring that began July 1, 2003 and ended June 30, 2004. The identifiers for the various sites are coded with letters A through E. There were 39 snowmelt runoff events and 74 rainfall runoff events during the year and a total of 299,000 gallons of runoff were sampled for sediment, dissolved reactive phosphorus (DRP) and total phosphorus (TP). The buffer efficiencies were over 90% for DRP, TP and sediment for the snowmelt events. For storm events, the buffer efficiencies were about 50% for DRP and TP and 57% for sediment for one buffer and 94% for sediment for a second buffer; this second buffer had ½ the slope and ¼ the contributing area of the first buffer so reasonably extracted more sediment and P.
The runoff from each of the farms is shown below for the rainfall and snowmelt
events. Some additional information is provided for the various fields.
The sediment loss from the various fields is shown below for rainfall and snowmelt events.
The p-losses from the various fields is shown below for rainfall events and snowmelt events separately. The results show both DRP and TP, TP being the larger values.