By: Doug Gass | South Skunk River Watershed Project Coordinator
Hilary Pierce presented on the effect of stream channel incision on groundwater depths for Iowa Learning Farms April 1 webinar.
Groundwater levels in riparian corridors can have a significant impact on nitrate removal. High groundwater levels keep soil saturated and create anaerobic conditions allowing for denitrification to occur. As streams incise deeper into the ground, they leave their banks less often and spend less time in the flood plain, which could create lower groundwater levels along the riparian corridors. For her masters degree research at the University of Minnesota, Hilary observed how stream incision impacted the depth of groundwater in these corridors.
Six sites were studied in southern Minnesota throughout the Minnesota River valley. The level of stream incision was classified for each site, along with a variety of other characteristics, including soil type, vegetation type, watershed area, and local groundwater discharge. Hilary and her collaborators then recorded how often the groundwater in these sites rose to within 50 centimeters of the ground surface.
This research found a significant relationship between streambed depth and groundwater levels, with more deeply incised streams having lower groundwater levels. Hilary also found that other factors had more significant impacts on groundwater levels in riparian corridors, with stream stage and local groundwater dynamics being the most influential factors.
In the future, Hilary wants this type of research to be expanded to include more sites in a wider geographic area. She is also doing regression analyses for predicting riparian groundwater levels. It is her hope that local factors such as precipitation, evapotranspiration, and stream stage can be used to create a model for predicting riparian groundwater levels at any site.
Join us next week, on April 8th at noon, for the webinar “Succeeding with Cover Crops & No-Till: A Guide for Spring 2020” presented by Liz Ripley & Mark Licht.