Characterization of prairie pothole inundation using AnnAGNPS under varying management and drainage scenarios

• Main Authors: Nahkala, Brady A., Kaleita, Amy, Soupir, Michelle L.
• Format: Text
• Language: English
• Published: Iowa State University Digital Repository 2021
• Subjects: Prairie Potholes; AnnAGNPS; Precision agriculture; Targeted conservation; Farmed wetlands; Agriculture; Bioresource and Agricultural Engineering; DML
• Online Access: https://lib.dr.iastate.edu/abe_eng_pubs/1217; https://lib.dr.iastate.edu/cgi/viewcontent.cgi?article=2502&context=abe_eng_pubs

Farmed prairie potholes are small, isolated depressions frequently classified as semi-permanent wetlands that make up a significant portion of land area in the Des Moines Lobe (DML) of the larger Prairie Pothole Region (PPR). Historically, these depressions have been subjected to significant drainage to improve their agricultural capacity. However, many assessments of the economic return of continuing to farm these depressions suggest that continued attempts to produce conventional row crops is not profitable and has other ecological consequences beyond crop drownout. This study expands the existing discussion of land use and drainage alternatives in a watershed modeling context. This study utilized the Annualized Agricultural Non-Point Source (AnnAGNPS) model to individually simulate the long-term hydrology of 6 prairie potholes using a matrix of land use and drainage modifications. Results suggest the presence of artificial drainage is the dominant factor in prairie pothole hydrology, while retirement and no-till practices can provide moderate reductions in flood inundation. Conservation tillage induces minimal change on flood metrics. Results show that average annual maximum inundated surface area is reduced by at most 50% across all simulations and the median annual days flooded could be reduced by 25 days, though this is less consistent when isolating high-precipitation years. Regardless of drainage status, in all scenarios there are, on average, more than two inundations events per year lasting 2–4 days. Longer events occur approximately once per year on average. Area inundation frequency curves suggest up to a 20% reduction in maximum pothole area inundated annually can be achieved at the 2-year return frequency. The availability of this data helps characterize the hydrology of farmed potholes more generally over a wide range of conditions, providing a reference for the prioritization of potholes for conservation or alternative management.