Developing design criteria to test a new saturated waterway conservation practice
Grassed waterways planted in upland drainageways are a common conservation practice to slow rainfall runoff and reduce soil erosion from agricultural fields. Less recognized is that the subsurface materials in these lowland areas are often filled with organic-rich deposits that could serve as natural bioreactors for reducing nitrate concentration in groundwater and tile drainage. Previous work funded by the INRC documented that grass waterway locations at an eastern Iowa site contained soil and biogeochemical conditions conducive for denitrification to occur, and nitrate concentrations in waterway groundwater were 70% lower than observed in groundwater beneath cropped fields.
In this new study, subsurface soil and groundwater conditions will be characterized across a wider range of waterway sites in Iowa and a hydrologic model will be developed to test the potential for development of a new conservation practice that utilizes the waterway deposits for nutrient reduction. The proposed practice would alter drainageway tiles to reconnect upland groundwater to the organic-rich drainageway deposits for nitrate reduction as saturated buffers do in riparian zones.
Up to 30 different waterway sites will be investigated by Schilling and his team at the University of Iowa and information from the field investigation will be used by Arenas at Iowa State University to model the performance of a new saturated waterway practice under a wide range of geologic and hydrologic conditions. At the conclusion of the project, the design for a new grass waterway practice will be developed that could be installed and tested at an appropriate site.