Dan Green Slough to go dry

(Photo by Russ Mitchell) Dan Green Slough is going to have a different look over the next two years as conservation officials drain water from the area. The process will allow wetland vegetation to get a start in the mud flats. It will also eliminate rough fish, which contribute to the murky conditions. [Order this photo]

Iowa Department of Natural Resources officials are trying to give Mother Nature a hand with some shallow waters in northwest Iowa.

They hope the end result will be cleaner wetlands for hunters and bird watchers to enjoy.

The centerpiece project in Clay County is under way at Dan Green Slough, which is about 4 miles east of Langdon along county road B17.

DNR officials are going to drain the slough -- a fish barrier is already in place to block unwanted rough fish from returning. A pump system is mostly installed and running. Contractors will continue to pump Dan Green Slough through fall so that water levels can be lowered enough to install the remaining intake tile this winter.

"We're pumping that to allow the contractor to come back in when it freezes up and install about 1,000 feet of pipe out into the marsh," said Iowa DNR Biologist Bryan Hellyer.

The finished project will be used for future drawdowns of the slough. The man-made measures are needed because marsh systems aren't as likely to empty out naturally in present-day Iowa. Advancements in agriculture have changed the way water drains on the landscape. Rough fish thrive in the murky conditions and contribute to the poor water quality by stirring up the sediment and disrupting vegetation.

The deepest part of Dan Green Slough is about three feet deep.

"You can't see two inches down," Hellyer said. "There are several reasons for that: They don't go through the drought process that they used to historically. Typically, every 10-20 years those marshes would go through a dry cycle. I'm not saying it won't happen again, but it is a lot more infrequent."

Wetland vegetation will grow in water, but the plants need to get their start in exposed mud flats during dry conditions.

"Northern pike were probably the only thing in the system historically," Hellyer said. "But now, the predominant fish out there are carp, bullhead and fathead minnows, which do nothing to help the system whatsoever."

Shallow lake projects also are under way in other parts of northwest Iowa. Diamond Lake in Dickinson County has been completely de-watered this summer and will have a fish barrier installed this fall. Late next summer, DNR officials say the lake will be allowed to fill and will be stocked with quality fish.

Also in Dickinson County, the Jemmerson Slough project is well under way as the water control structure and fish barrier have been installed and most of the electric pump system is in place.

Weather permitting, Jemmerson Slough will be kept nearly dry through late summer 2010 to achieve desired biological results.

"Simply stated, the goal of these and future shallow lakes projects is to restore health to these basins so that they once again contain clean water and are of increased value to wildlife and humans," the DNR said in a statement. "Historically, wetlands and shallow lakes maintained health by going through natural periodic droughts. Through the drought process, problem fish that stir up bottom sediments were eliminated and loose bottom sediments were consolidated and exposed to sunlight, thereby allowing for the germination of aquatic plants that provide habitat and help purify water."

Since many lakes no longer dry naturally, biologists now use intensive management strategies like gravity flow water control structures and pumps to replicate drought conditions and fish barriers to slow the re-infestation of problem fish back into healthy systems.

Quality fish will be stocked in the shallow lakes where adequate depth will allow for survival over the winter months. The DNR will take predatory control over less desirable species that will find their way back into the lake over time.

In wetlands and shallow lakes that frequently freeze out, no fish will be stocked and intensive efforts, including partial winter de-waterings, will be used to keep problem species at bay.

"For those who enjoy waterfowl hunting, wildlife viewing, or simply looking down into clean lake water, these are exciting times," the DNR's statement continued. "A strong partnership between the Iowa Department of Natural Resources, Ducks Unlimited, the North American Wetland Conservation Act, local landowners, and others promises to continue its effort to return health to these important northwest Iowa aquatic systems."