Willow Creek Dam 'did what it was designed to do' during historic flood event

PIERCE -- The Lower Elkhorn Natural Resources District (LENRD) continues to monitor the infrastructure across the area following the historic flooding events of the past week.

LENRD General Manager, Mike Sousek, said, “Without the investments that previous community leaders put into place years ago, this historic event could have been much worse.  Without the Willow Creek dam 1 ½ miles southwest of Pierce, and the Flood Control Levee protecting Norfolk, these cities would have been under water.”

On average, the Willow Creek reservoir holds back 7,100 acre-feet of water.  As of Friday, March 15th, with the historic flooding occurring across the area, Willow Creek was holding back over 18,000 acre-feet of water.

An acre-foot is a unit of volume commonly used to reference large-scale water resources, such as reservoirs.  It is defined as the volume of water necessary to cover one acre of surface area to a depth of one foot.  An acre-foot is equal to 325,851 gallons of water.  If you take that number times the 18,000 acre-feet of water that Willow Creek held back during the storm, you get 5.86 billion gallons of water.  Sousek said, “When you attempt to visualize that amount of water, you can begin to fully understand how critical this dam is to the area.”

Sousek added, “The Willow Creek flood-control structure continues to do its job.  It’s doing exactly what it was designed to do.  The dam held back water that would have otherwise affected the communities of Pierce, Hadar, and Norfolk as well as the streams along the Elkhorn River and downstream landowners, county roads, and bridges.”

To understand the way the dam functions, we need to explain some of its inner workings.  In the dam at the Willow Creek State Recreation Area, there are 27 pressure relief wells across the earthen structure.  These 27 wells relieve the pressure that occurs naturally as water pressure pushes the water up, similar to an artesian aquifer or well.  The relief wells relieve the pressure on the dam and prevent the water from pushing through and eroding a channel under or near the dam.  The relief wells drain into a collection pipe which drains into another collection pool and then finally ends its journey as it drains into the “stilling basin” which is located on the east side of the dam.  The stilling basin allows the water to slow down before it is released into the channel.  Along with the relief wells there are piezometers on the dam that the LENRD uses to monitor the changes in the water levels.  The piezometers measure the depth of water and how high the underground pressure is pushing the water up.  The LENRD staff use the relief wells, the piezometers, and other variables to monitor the structure to determine if it’s functioning properly.

Sousek continued, “Not only did the dam help to alleviate further damages to downstream landowners, towns, and villages, but it also helped protect the levee in Norfolk.”

He said, “We continue to monitor our structures and remain confident in their worth.  Investments in flood control levees and dams strengthen and preserve communities.”

Thank you to all the volunteers who helped during this unprecedented storm as well as those who assisted the LENRD staff as they monitored the Willow Creek Dam, especially the members of the Pierce Volunteer Fire Department.

The Willow Creek State Recreation Area is owned by the LENRD and is managed by the Nebraska Game & Parks Commission.  To learn more, sign up for our monthly emails.