Pool 5 drawdown on course (2005-09-06)

Tom Conroy Information Officer DNR Southern Region 261 Hwy 15 South New Ulm MN 56073 507/359-6014 tom.conroy@dnr.state.mn.us 

September 6, 2005

For additional information, contact: Tim Schlagenhaft, DNR Community Outreach Coordinator, Rochester (507-280-5058).

Pool 5 drawdown on course

They're like buried treasures, millions of them, just waiting to be uncovered.

These treasures are dormant aquatic plant seeds, invisible below the water, embedded in mud. And until they are exposed to sunlight and air, they will remain dormant, their potential value unrealized. Under the right conditions, however, these dormant seeds can blossom into thriving stands of aquatic plants that improve water quality and provide tremendous value to fish and wildlife.

Tim Schlagenhaft, Minnesota Department of Natural Resources (MDNR) Community Outreach Coordinator and Mississippi River Team leader, said water level fluctuations create conditions aquatic plant seeds require in order to germinate. Such fluctuations used to occur naturally and regularly on the Mississippi River until the construction of locks and dams changed this cycle.

"The construction of locks and dams in the 1930s and their management for commercial navigation has restricted Mother Nature's ability to provide low water conditions," Schlagenhaft stated. "As a result, vast beds of aquatic plant seeds never get the chance to germinate."

To counter this situation, natural resource professionals can sometimes step in and lend Mother Nature a helping hand. In the case of the Mississippi River, dams can be used to lower water levels and expose the mud flats, Schlagenhaft said.

To achieve these resource objectives, the U.S. Army Corps of Engineers, St. Paul District, in cooperation with the Water Level Management Task Force of the River Resources Forum, began implementing a drawdown of Pool 5 for the benefit of fish and wildlife this summer.

A successful example of this practice, Schlagenhaft noted, occurred at Pool 8 on the Mississippi River in 2002. Another drawdown began on June 13 of this year at Pool 5, an area that includes portions of the legendary Weaver Bottoms.

According to Schlagenhaft, the Pool 5 drawdown is "creating a vegetative response very similar" to the Pool 8 drawdown that exposed about 2,000 acres of mud flats. These areas were eventually colonized by annual and perennial vegetation and immediately began to attract fish and wildlife. Once the plants become established, water levels are raised. The Pool 5 drawdown is expected to expose about 900 acres.

The full 1.5-foot drawdown was initially reached at lock and dam #5 in late June but high water flows at the time reduced the extent of the drawdown in the middle and upstream portions of the pool, according to Jeff DeZellar, Project Manager for the St. Paul District Corps of Engineers. As flows eventually dropped into a more normal summer range, more of those areas also became exposed.

However, flows continued to drop and by late summer were well below normal, forcing the Corps of Engineers to raise water levels slightly at the dam to ensure adequate depth for commercial navigation, DeZellar explained. This again resulted in a reduction of the area exposed by the drawdown.

"Changes in flow conditions during the course of a summer is not unusual," DeZellar said. "It's one of the difficulties associated with planning and successfully implementing drawdowns."

Schlagenhaft said the drawdown did create some problems for recreational boaters at a few sites. However, surveys indicated that there was enough depth for navigation in these areas and travel lanes were marked, reducing the problems.

"Pelicans, sandhill cranes and a variety of shorebirds have been showing up on the mud flats and both annual and perennial plants have sprouted in impressive fashion," Schlagenhaft stated. "We know we won't be able to completely re-create conditions on the river as they once were but we can at least improve on what we now have."

If adequate water flows for navigation continue, the drawdown will continue until mid-September at which time levels will be raised with the goal of reaching full pool elevation by October 1.

The Pool 5 drawdown was endorsed by the River Resources Forum (RRF), a consortium of state and federal agencies that make recommendations on navigation and habitat restoration to the U.S. Army Corps of Engineers.

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