Blue Earth County Ditch No. 57
Minnesota | Water
ISG-designed county ditch project demonstrates practices to boost agricultural production and improve water quality.
County Ditch No. 57 was an ideal site to test water storage and drainage strategies to provide empirical evidence of the effects of Best Management Practices (BMPs).
Mapleton Area Agricultural + Urban Runoff Analysis Phase I
Recognized as the first public multi-purpose drainage project in Minnesota, Blue Earth County Ditch No. 57 (CD 57) provided proof to landowners and agencies that conditions for agricultural production were enhanced, peak flow rates reduced, and water quality was improved by implementing a combination of BMPs on CD 57. Water storage and drainage capacity was increased, which reduced flooding and improved field conditions for crop yields, and water quality also saw marked improvements in the reduction of sediment and nutrient loading throughout the system. The CD 57 project implementation and Phase I analysis was awarded $485,000 through Legislative – Citizens Commission on Minnesota Resources Minnesota and Environmental and Natural Resources Trust Fund (LCCMR/ENRTF).
A combination of BMPs included two water storage basins, buffer strips, two-stage ditch, and a rate control weir. The two storage basins significantly increased storage capacity, with the Klein Pond providing 26.3 acre-feet of storage and the City Pond providing 23 acre-feet. Peak flow rates were reduced from 10% to 50% at Klein Pond, and the rate control weir averaging 6% in reduction for monitored rain events. In addition to helping the system better manage rainfall events, results from the three BMPs monitored showed they removed a total of 1,059,630 pounds of sediment from 2011 to 2014, equivalent to nearly 40 dump truck loads. The success at CD 57 serves as an example of how focused designs can benefit both landowners and the environment simultaneously.
Agricultural + Urban Water Quality Treatment Analysis Phase II Report
Upon completion of Phase I, the need for continued and more detailed monitoring was identified, as well as a gap in available information on maintenance recommendations of BMPs with associated costs. An additional $105,000 was awarded by LCCMR/ENRTF to continue monitoring CD 57 from 2016 to 2017 to determine long-term effectiveness of BMPs, identify maintenance recommendations, and analyze BMP lifetime cost-benefits. Phase II analysis refined monitoring methodology and findings from targeted site locations, including Klein Pond, the two-stage ditch, and the rate control weir.
Results showed the BMPs continued to provide water quality improvements to the watershed, with Klein Pond being the most cost-effective BMP. Klein Pond also continued to provide storage for the watershed, reducing peak flow rates on average by 25% and providing water quality benefits. Due to the capture of sediment in Klein Pond, the analysis identified the need for maintenance and clean out of the pond’s sediment trap. Over time, the pond accumulated an additional 382,590 pounds of sediment, and as a result, its ability to capture sediment was significantly reduced. Continued maintenance to BMPs was found to play an integral role in long-term BMP effectiveness.
This project was funded by: