2026 March Stewardship Advocate

Mapping structural conservation practices in Iowa

The Iowa Nutrient Reduction Strategy (INRS) was developed in 2013 by the Iowa Department of Agriculture and Land Stewardship (IDALS), Iowa State University (ISU) and the Iowa Department of Natural Resources (IDNR). The INRS is a science and technology-based framework to assess and reduce nutrients entering Iowa water bodies. It is designed to direct efforts to reduce nutrients in surface water from both point and nonpoint sources in a scientific, reasonable and cost-effective manner. A key element of the strategy is measuring progress over time and releasing progress reports to the public.

Using sensor technology, ISU assembled a baseline of practices from 2007-2010 of up to 40,000 acres of watershed level including: terraces, water and sediment control basins (WASCOB), grassed waterways, pond dams, contour strip cropping and contour buffer strips.

There are several conclusions to draw based on the mapping of these three practices:

1. Landowners and farmers have constructed many of these practices since the 1980s. This can be seen by comparing the density of practices in the Silver Creek HUC in northeast Iowa. For example, the miles of terraces (shown in orange on the maps) increased by 276% between the 1980s and 2016, while the miles of WASCOBs increased by 8400% in the same time period.

2. Researchers can now look at a watershed scale to not only determine where terraces and WASCOBs are currently located but can also identify areas on the landscapes that could benefit from constructing additional terraces and WASCOBs. Below is a map of the Wolf Creek watershed in southeast Iowa showing the location and length of terraces and WASCOBs. By using  other digital technologies, it is possible to estimate the saturation of a practice and the potential to install additional terraces and WASCOBs. In this watershed, there are 353,000 feet of terraces and WASCOBs which is 91% of the possible locations suitable for these structures. This leaves only 33,500 feet of potential terraces that could still be built in the proper position in this watershed to achieve 100% coverage of terraces in the Wolf Creek watershed. This is a clear example of farmers and landowners recognizing the need to reduce soil and runoff and putting in terraces and WASCOBs to do so.