As portions of Benton Lake dry out, habitat improves

Anyone who is used to going to Benton Lake National Wildlife Refuge to look at birds will notice a marked difference this year.

The refuge's unit 2, which has traditionally been the centerpiece of its auto tour route, is much drier than usual.

Allowing that unit to go dry is part of Benton Lake's 15-year comprehensive conservation plan that was adopted in early 2014.

That plan calls for less water to be pumped into the wildlife refuge while continuing to provide some waterfowl hunting and fall and spring migration habitat for birds.

While it may seem counterintuitive, allowing parts of the refuge to dry out actually benefits migrating birds and other wildlife, refuge manager Rob Bundy explained.

"We want to simulate natural events," he said.

Despite its name, Benton Lake really isn't a lake at all. It's a 5,000-acre shallow wetland that was designated as a "refuge and breeding ground for birds" in 1929. Lake many natural wetlands, Benton Lake was often dry, depending on precipitation and runoff levels.

Like many wildlife refuges throughout the nation, Benton Lake was originally established as a refuge and breeding grounds for migratory birds. Early staff recognized that water was the limiting component to meeting waterbird production targets, so in the early 1960s, a pump was constructed on the Muddy Creek drainage to bring water from the Fairfield Bench to the refuge. An extensive series of levees and water control structures were constructed to divide the area into units.

Naturally, Benton Lake would be a seasonal wetland, but the addition of pumping and irrigation created a more permanent wetland.

For more than 60 years, water pumping would begin in August and last about two months, pumping 80 acre-feet per day, which was usually enough to flood all of the refuge's six units.

That pumping was problematic for several reasons: It was expensive, it was unnatural to have the same water levels year after year, and it was leading to a build up of selenium, which can cause bird eggs to be deformed or infertile.

The refuge's new comprehensive conservation plan aims to fix all of those problems, and, so far, the staff is seeing improvements, Bundy said.

"We're seeing some things happen out here that we haven't seen in 60 years," he said.

Plants they haven't seen in a long time have returned to the refuge. Strategic drying changed the forage and bugs that were available for birds to eat. And bird species that had dropped off at the refuge are now spotted frequently. Meadowlarks are using the shrubs in the area, burrowing owls are showing up, and pheasants are nesting in higher numbers.

"We've got a whole new complement of species," Bundy said.

Managers will continue to pump water into the refuge at least 11 out of 15 years, but the amount of water will be greatly reduced.

In recent years, the bill to run the pumps was about $80,000 a year.

With reduced budgets, spending that much to pump water is no longer an option, Bundy said.

"The pumping budget went away," he said.

Benton Lake will now spend about $40,000 a year running its pumps, which is enough to pump for 30 days, and fill some units of the refuge.

"We can't afford any more and the marsh doesn't need any more," Bundy said.

However some years, no pumping will occur. The plan calls for pumping any year that runoff produces at least 100 acre feet of water. With any less water, pumping would be fruitless. It would just be absorbed into the dry soil and never actually fill the basins.

This year, the refuge saw 200 acre feet of water, which isn't much, but is enough to turn on the pumps.

However, this year water wasn't pumped into unit 2.

"You've got to dry out units every once in a while," Bundy explained.

Flooding a unit to the same level year after year cuts down on the biodiversity of the plant life in the area and gives birds less to feed on.

"Fluctuation is actually the best thing that can happen," he said.

That constant flooding has also caused a build-up of selenium at Benton Lake.

Selenium occurs naturally in underground marine shale. When water seeps down into that shale, it picks up selenium and then comes out of the ground in saline seeps within the refuge.

Allowing areas of the refuge to go dry helps with the selenium problem because when selenium is dry it can vaporize and be released into the atmosphere. Managers have also found that certain plants remove selenium from the soil. Those plants can then be harvested or burned.

Unit 1 has the most selenium build up, with 10 parts per million. Two parts per million is the threshold to start being concerned.

With unit 2 drying out this summer, Benton Lake rerouted its auto tour.

"We're not hung up on traditional auto tour routes," Bundy said.

However, unit 2 is still worth a visit.

Shorebirds can still be spotted as they search for meals in the remaining water.

"That receding water concentrates the bugs that they're feeding on," Bundy said.

It's hard to watch a marsh go dry, until you realize it's an important part of the natural process, he said.