McCook Lake

McCook Lake has been preserved through community involvement. Its presence has created a housing renewal area for North Sioux City.

Editor’s Note: McCook Lake is an important asset to the area. We have worked with the McCook Lake Association to give our readers background information and an update on the lake. We see this as a periodic feature.

The Nov. 11 edition of the Dakota Dunes/North Sioux City Times carried an article about releases from Gavins Point Dam. One often-overlooked effect of these releases along with Missouri River water flows is the level of McCook Lake.

Dating back to the times of Lewis & Clark, the lake began as an oxbow of the Missouri River. Over time, the river’s course changed, leaving behind what is now known as McCook Lake. In its current state, the lake covers about 273 acres. It collects run-off from about 600 acres of ground; the complete watershed includes about 3,000 acres. When full, the lake holds about one billion gallons.

Because of its proximity to the Missouri River, river levels have a direct impact on McCook Lake’s levels. When the river is high, ground water reservoirs fill up and the lake naturally adjusts to a higher level. When the river is low, the lake follows suit.

For example, during the summer of the 2011 flood, the river elevation was 10 feet higher than the lake, resulting in groundwater entering the lake at a rate of one inch per day. This summer, when the river was historically low and the river was 10 feet lower than the lake, the lake drained about one inch per day.

Because of this relationship, natural means are not enough to keep the lake filled. To achieve the ideal lake level, the McCook Lake Association maintains a pumping system consisting of a 400-horsepower vertical pump located at the river and a 7,500-foot long, two-foot diameter pipe connecting to the lake. The pump, which typically runs from spring to early October, is capable of moving 11,000 gallons per minute, equivalent to raising the lake by two inches per day.

In the summer of 2021, the pump continuously operated at near capacity to maintain the lake level at an elevation of 1088. The river level was historically low, resulting in a large drop in groundwater level. As a contrast, just two years ago in 2019, the river was historically high, raising the lake level above the target level of 1088. The association moved a 60 horse-power pump from the river to the lake and pumped the excess water back to the river.

The association’s mission is to maintain the integrity of the lake for the use of recreation, boating, fishing and swimming as well as to improve the natural environment of the lake for wildlife. The association operates and maintains the pumping system, places the no-wake buoys, monitors the water quality, represents the members in political matters and raises money for the 4th of July fireworks. There are 11 volunteer board members, truly a working board. Average expenses are $60,000 per year. The largest expenditure is for the electrical power, which was $35,000 this year compared to $25,000 on average. Revenue for the association is from corporate and city donations, memberships and the annual Admiral’s Stag fundraiser.

Additionally, the association has worked hard to minimize erosion of the lake bed. This helps keep pumped-in water in the lake. Examples include working with the city to stabilize the lake bed where storm drains connect to the lake and the 2018 construction of a poured concrete disperser where the river pipe enters the lake.

There are about 210 lakefront properties on the 3.1 miles of “outside shore” of the lake. The “inside shore” is a nature preserve, owned and managed by the Izaak Walton League of McCook Lake. Lakefront properties have an assessed value of $45 million, resulting in a property tax of about $800,000 per year. These values have increased by over 50 percent in just the last five years and will continue to increase as more houses are built or remodeled.

McCook Lake is a community resource that shouldn’t drain away. Vounteers’ time and financial contributions assist in keeping the lake an exhilarating place to be. Anyone who is interested in becoming a member or volunteering with the McCook Lake Association can find information online at mccooklakesd.com.