Posted on November 17, 2020
By Laura M. Fleming, President and CFO of SRS Crisafulli, Inc.
Outbreaks of blue-green algae in a 1,616-acre natural lake, created an emergent call to action in the 1990’s from the community of Powers Lake, North Dakota. Due to blue-green algae blooms, the recreational value of Powers Lake plummeted and few people gathered or recreated there.
Powers Lake Watershed Committee (PLWC)
In 1998, the local community recognized the importance of Powers Lake and formed the Powers Lake Watershed Committee (PLWC). They initiated the water quality improvement project in Powers Lake which is fed from a 44,458 acre watershed. Improving water quality requires funding, cooperation, and action.
PLWC applied for and received three federal 319 grants of the Clean Water Act in 2003, 2011 and 2016 and the community provided local match requirements with funding, cash and in-kind services. The project also received a grant in 2017 from the North Dakota Outdoor Heritage Fund.
In 1999, PLWC initiated a watershed assessment and Agricultural NonPoint Source (AGNPS) model, which was completed in 2001. The watershed assessment and AGNPS model recommended watershed restoration actions, established pollutant reduction goals, and provided a method for evaluating progress. The watershed assessment revealed the lake received an annual phosphorus load of 11,564 pounds with 6,339 pounds entering the lake and 5,225 pounds within the lake. The water analysis measured Powers Lake as “hyper-eutrophic” with excessive nutrient loadings, specifically, high levels of phosphorous and low dissolved oxygen levels. To meet state water quality standards and improve water quality required reducing nutrient loads entering the lake by seventy-five percent and nutrient cycling within the lake by fifty percent.
Conservation to Prevent Nutrients from Entering the Lake
Agriculture production is the economic foundation of the Powers Lake area community and agricultural pollution was a significant source of pollution entering Powers Lake. Agricultural producers changed practices and adopted Best Management Practices BMP’s for soil and water conservation to prevent nutrient loads from entering the lake. Farmers switched to no-till or minimum till, fallowed fewer acres and reduced the quantity of fertilizers applied across the watershed. Ranchers installed wells, pipelines, tanks, fencing and implemented grass seedings and grazing rotations. The cooperation and actions of the agricultural community resulted in fewer nutrients flowing through the watershed into Powers Lake.
The data indicate the watershed conservation activities are effective at preventing nutrients from entering the lake through erosion and runoff. The water quality measurements between 2001 and 2009 indicate that Trophic State Index (TSI) scores improved. In 2009, the average TSI score for chlorophyll a was 53.24, which met the goal of a total maximum daily load (TMDL) target of 55.02.
Legacy Phosphorus in the Lake
After the conservation activities, phosphorus TSI scores remained high and held steady at 85, which is considered “hyper-eutrophic”. The likely cause was legacy phosphorus within the lake continually cycling from the lake’s sediments. In 2008, PLWC sought solutions on how to reduce the internal nutrient cycling which was feeding blue-green algae blooms. Houston Engineering Inc. was hired and completed the Powers Lake Nutrient Management Alternatives report in October 2009. They recommended dredging as the best remediation method to reduce internal nutrient cycling.
Dredging to Remove Overabundance of Nutrients
In 2015, the City of Powers Lake purchased a Montana made Crisafulli Rotomite hydraulic dredge. The PLWC Coordinator has been dredging sediments from the lake for five seasons. As of 2019, 50,900 cubic yards of sediment which includes 80,273 pounds of phosphorus and 32,020 pounds of nitrogen have been dredged out of the lake.
Results of Conservation and Dredging to Improve Water Quality
Significant declines in total phosphorus levels indicate the combination of conservation activities and dredging are effective actions toward continued water quality improvement. Prior to the initial project in 2001, dissolved phosphorus constituted 45.9% of total phosphorus. During the conservation implementation phase in 2006 and 2007, dissolved phosphorus constituted 50.3% of total phosphorus. During the dredging phase of the project from 2015 to 2019, dissolved phosphorus constituted 72.6% of total phosphorus. Combined with declines in total phosphorus, the significant change in the ratio of dissolved phosphorus to total phosphorus from 50.3% during the conservation implementation phase to 72.6% during the dredging phase indicates removing sediment-bound nutrient sources via dredging is highly effective.
The community of Powers Lake followed their motto of A lake is a reflection on the community that lives within its watershed by improving the water quality in the lake. For more than twenty years, people have been contributing to the common goal of improved water quality. They include PLWC, farmers, ranchers, the City of Powers Lake, Mountrail Soil Conservation District(SCD), Burke SCD, NRCS in Mountrail and Burke Counties, US Fish and Wildlife Service, Burke County Extension Service, North Dakota Natural Resource Trust, Upper Dakota RC&D, North Dakota Game and Fish, Ducks Unlimited, and the many volunteers.
Opinions expressed here do not necessarily reflect those of the Sustainable Phosphorus Alliance.
About the author
SRS Crisafulli, Inc. is a manufacturing company located in rural eastern Montana that celebrates and supports resourceful communities and clean water. They specialize in sludge removal systems for municipalities, industries, and lake communities.