Wetland Hydrology & Biodiversity in the Red River Basin, Minnesota - Technical Paper No. 12

This study examined the relationships between water level bounce and biodiversity in 28 natural and restored wetlands throughout the Red River Basin, Minnesota. The hydrology of each wetland for a 20-year period was projected using two years of recorded water level data and water budget modeling to determine the magnitude, duration, frequency and hydrograph behavior. The study found that wetlands provided more spring and summer flood water storage than anticipated by the project hydrologists and less adverse impacts due to bounce than the ecologists expected. Relationships between plant, bird and macroinvertebrate diversity with hydrology, land-use and other parameters were evaluated using parametric and multivariate analyses. Weak relationships were found with hydrological variables and stronger relationships with watershed land-use variables. The wetlands studied fell into three quality categories that can serve as potential wetland restoration siting criteria for use by project teams in Flood Damage Reduction programs in the Basin. In this study, high quality wetlands were found to have low amplitude and low frequency bounce events, and medium and low quality wetlands to have durations generally meeting a 10-day bounce draw down and 2-3 foot bounce amplitude. Previous TSAC recommendations of bounce criteria of 2-3 feet and the draw down rates of 90% of the volume in the bounce hydrograph reduced in 10 days are supported by the analysis in this study. Additional recommendations are provided in this study. This study did not investigate site specific wetland restoration objectives or concerns such as the effects of bounce on over-water nesting birds during the nesting season. Additional research such as this is suggested.