Mapping Nutrient Runoff Risk in the Red Cedar Watershed

Abstract

Lakes and streams across the Midwest face nutrient pollution that disrupts freshwater ecosystems. Nitrogen and phosphorus are natural parts of the ecosystem, but too much can create serious problems. The green lakes, a result of algal blooms, are an example. One of the main sources of nutrient pollution is runoff from farmlands. After a rain or snow melt event, nutrients that are not used by crops can be washed into nearby waters. And nutrients are more likely to end up in the watershed if applied to areas close to nearby waterways or areas with a steep slope. Many conservation practices are available to reduce nutrient runoff such as conversion to pasture, grassed waterways, nutrient removal wetlands, and more.

This summer, I mapped areas of cropland in the Red Cedar Watershed and their risk of nutrient runoff. To accomplish this, I used GIS (geographic information systems) to combine variables of slope, distance to water, and land cover. The combination of data led to a risk scale map that shows runoff risk across the watershed.

To achieve the desired results, I used GIS, which is a computer-based means for mapping and analyzing spatial trends and relationships. Generally, GIS allows us to answer questions about where problems occur and how can we better understand and visualize data to address them Throughout I used data layers, or collections of data, such as a set of points with coordinates. The process used a variety of tools to convert available data from the Wisconsin Department of Natural Resources to the final product.

First, cropland was selected from a land cover dataset. Then, slope was calculated from an elevation dataset. Next, the separate datasets of lakes and streams were combined. With the combined waters, the distance from each pixel, or point in the watershed, was calculated. Index values, which simplified risk to a rank from 1 to 5, were assigned to the slope and distance to water layers. The indexed layers were then merged to create a map of cropland with a runoff risk scale. In the end, 41.4% of cropland in the watershed was found to be at high risk of nutrient runoff.

I chose to focus on the Red Cedar Watershed because a third of the land is used for cropland and algal blooms are common. The waters within the watershed are important to nearby communities, but having toxic lakes makes outdoor recreation and other uses difficult. The Red Cedar Watershed, is not alone in struggling with nutrient pollution, as many watersheds across Wisconsin experience the same problems.

My hope is that this project will help the community in dealing with nutrient pollution in the lakes and rivers. These maps are a way for the community to visualize the distribution of the issue and identify where to focus their attention to make the greatest improvements in watershed quality. With proper funding and education, there is large potential throughout the Red Cedar Watershed for the reduction of nutrient runoff. And the application of conservation practices to any cropland would make a positive impact regardless of runoff risk.

In my completed analysis, I used steep slope and close distance to water as variables. In the future, a variable like soil characteristics could be added. Particle size or compaction could change the runoff risk and improve the results of the analysis with their inclusion. In addition, this project could be expanded by looking at past or future runoff risk in the watershed, or the economic impacts of the conversion of cropland to pasture. Next time, an analysis like this is conducted, I recommend a greater emphasis on using knowledge from, and communicating with, the community.

Overall, this project has been a wonderful experience, expanding my perspectives on both research and environmental issues. The LAKES program has provided me with an incredible opportunity to collaborate with students across various fields, allowing me to gain interdisciplinary problem-solving skills that will improve the way I understand and address problems in the future. Working with other fields of study on similar issues has been eye-opening, provoking me to consider social and economic concerns I had not considered before. In addition, I have received valuable insight into how scientific research is conducted, as well as improved analytical skills, which I can use regardless of career. With the various presentations, I have become more confident in writing and presenting scientific projects. I have also expanded my GIS abilities, learning new tools and methods.

In addition to our research, I have enjoyed getting to know my fellow researchers from across the country and taking time to explore Menomonie. It has been great biking around town and seeing new places. I have personally seen much of Menomonie through my binoculars, as I have visited many parks while birding. The Red Cedar River and Lake Menomin have proven to be terrific areas to find some cool birds, as well as scenic views. In the end, I am grateful for the experience here in Menomonie and the chance to do research on such a crucial problem. Moving forward, I plan to retain the new perspectives I have gained and to address the environmental issues we face with determination.