Spring Nutrient Levels in Drained Wetlands of IOWA’s Prairie Pothole Region

Abstract

Approximately 95% of nearly 4 million acres of wetlands located in Iowa’s portion of the Prairie Pothole Region (Des Moines Landform Region) are currently drained and farmed for row crop agriculture. Many of these wetland basins are too wet to produce consistent crop yields and too dry to function as normal wetlands. Very little information currently exists that documents what, if any value, drained wetlands may have in terms of water quality, wildlife usage and/or habitat, and hydrologic functions. A four-year comprehensive study of drained wetlands was conducted from 2011 to 2014 to develop baseline conditions and to document the current status of drained wetlands in the Des Moines Lobe region. As part of this comprehensive study, nutrient levels were analyzed from surface water collected in drained wetlands during the spring months. Nitrogen and phosphorus concentrations showed high intra- and inter-annual variability and maximum concentrations for nitrate and ammonia exceeded aquatic life benchmarks. Nutrient levels in drained wetlands were significantly higher as compared to data previously gathered (2005–2009) from restored prairie pothole and high quality reference wetlands in the same region. Information from this study advances our collective knowledge of drained wetlands for both conservation and land-use policy related decisions.