A huge benefit for Spring Lake at a low cost

Spring Lake, a heavily-used local gem, but now on the state’s Impaired Waters list because of its turbidity, can be restored to clarity at surprisingly little cost.

Greene County conservation director Dan Towers has already been working with the Iowa Department of Natural Resources (DNR) toward that goal, and it may be achieved in the near future.

The 50-acre lake is pretty much opaque below a foot or two of depth, but not because of runoff from nearby fields or farm tiles. There’s really not much of a watershed at all that drains into the lake, located in Hardin Twp. about seven miles northwest of Grand Junction or 10 miles northeast of Jefferson.

The cause lies with the carp that inhabit the lake.

Carp are bottom feeders, and they stir up the silt on the bottom of the lake, making the water cloudy.

The answer: Get rid of the carp.

To do that would cost an estimated $20,000. And the DNR has grant money that could cover the expense.

Towers thinks the DNR would place Spring Lake high on its project list, and that a grant could likely be soon forthcoming.

DNR officials, in consultation with Towers, suggested first treating Pound’s Pits, located south of Spring Lake, to see how successful it might be. That was done last year. Treatment involves putting rotenone, a chemical toxic to fish, into the water to wipe out the existing fish population, including the carp, then restocking with desirable fish, such as bass, bluegill and channel catfish.

Many Greene County residents, including me, thought the problem at Spring Lake was the population of white amur (grass carp) that were introduced into the lake in 1979 by the DNR, at a rate of 10 per acre, a total of 500 fish.

Spring Lake had become heavily clogged with aquatic vegetation, making fishing from shore very difficult because of weed snags. The grass carp, as their name indicates, were stocked into the lake to devour the vegetation, which they did very efficiently.

But 10 per acre were too many, and before long all the vegetation was gone, and small bait fish had no habitat cover. The fishery deteriorated.
But the grass carp, according to Towers, didn’t stir up the bottom silt very much, and they have mostly disappeared by now anyway.

The turbidity problem emerged in the floods of 2008. The high water in Buttrick Creek, which flows out of the spillway at the southeast corner of Spring Lake, overflowed the spillway and allowed regular river carp, as opposed to grass carp, to swim back into the lake and start reproducing there.

Those regular carp are the source of the lake’s turbidity. When water is too cloudy, sunlight can’t reach the bottom, and vegetative growth is consequently impossible.

A third cause of the poor fishery of the lake, in addition to the lack of vegetation and the turbidity, is overfishing of the bass that could otherwise keep the bluegill population under control, Towers said. There’s a 15-inch minimum keeper limit at Spring Lake for largemouth bass, but that’s a hard thing to regulate and enforce, and in addition, bass are sometimes harmed even if a fisherman practices “catch and release.”

The result is too many stunted bluegill who compete with each other for food.
Rotenone, to eliminate the carp, both the bottom feeding variety and the larger grass carp that consume vegetation, would solve both the turbidity and the lack of weed cover. Restocking with desirable game fish would then improve the fishery.

Remaining challenges, according to Towers, would be how then to keep the vegetation under control, and how to discourage overfishing of the bass population. But those problems are certainly preferable to the present situation.

Spring Lake, owned by Greene County since 2002 and managed by the county since 1969, is a very popular spot in our region of Iowa. Kathy and I drove around the camping areas there on Sunday this past weekend; we saw vehicles, including the many campers and RVs, from Greene, Dallas, Boone, Calhoun, Carroll, Polk, Warren, Story and other counties.

According to Towers, there are 124 camping sites with electrical hookups at Spring Lake, and many other tent camping sites. On a holiday like Memorial Day weekend, at least 150 sites are occupied, averaging 3.3 people per site, for a total of about 500 folks. In addition, many of them are joined by friends and family at some point during the weekend.

The site dates back to 1866, when the Chicago and NorthWestern railroad started digging gravel for its main line across Greene County a few miles south. The high water table in the area eventually filled the dig with water, and the result is what we enjoy today, as have area residents for many generations.

Spring Lake is the county’s only multi-use recreational lake, and the Greene County Conservation Board has done a wonderful job of maintaining and improving it.

We applaud the plans to upgrade the lake’s fishery, and hope the DNR awards a grant for that purpose in the near future.