Natural fertilizer from geese creates unwanted vegetation in city's lakes

Canada geese eat a lot and anyone who has visited Radio Springs or Walton lakes in recent weeks knows where all that food ends up.

While the goose waste creates a hazard to the shoes of people walking around the park, it creates a bigger problem for the lakes and the fish that dwell in those lakes.

"Each goose produces 1/2 pound of manure each day and 24 geese will produce over one ton of manure a year. I've seen as many as 200 on Radio Springs Lake," Tom Priesendorf, Missouri Department of Conservation fisheries biologist, told the Nevada Parks Board last week.

When it rains much of that organic fertilizer goes into the lakes and helps the vegetation in the lakes grow. Lately, it's been helping lake vegetation to thrive too well.

"It causes a major vegetation problem," Priesendorf said.

He said that the geese are problem on both lakes, but Radio Springs is more sensitive, because the water is clear.

The clear water lets more light reach the bottom of the lake, which also encourages vegetation growth.

In 2001, as one of the parks sales tax capital improvement projects the city had Radio Springs Lake drained and deepened. To help with improving the fishing at both Radio Springs and Walton Lakes, the city entered into an agreement with the Missouri Department of Conservation for them to manage the fisheries in both lakes.

Even though the city had Radio Springs Lake dredged, Priesendorf said the lake is still much more shallow than the Conservation Department thought it would be.

"There is a continual problem with the shallow depth of Radio Springs," he said.

He said that some areas of the east end of the lake are 10 to 11 feet deep, while the west end is more shallow than that.

"A lot of the west end is only five or six feet deep and with the clear water, there's lots of vegetation," he said.

That's because when the lake was being dredged, the contractor unexpectedly ran into a rock ledge in the west end of the lake that prevented them from making that part of lake as deep as the rest of the lake.

Priesendorf said that in 2006, the city dodged a major fish kill at Radio Springs. There was a minor fish kill due to low oxygen levels in the lake.

"It was on the verge of a complete and total fish kill," he said, but the Nevada Fire Department came to the rescue and used their equipment to re-circulate the water and add oxygen.

"Without those efforts, we would have been back to square one," he said.

Since then the city has installed aerators on the lake, which helped with the low oxygen problem.

The huge nutrient load from the goose manure is the primary cause of the oxygen depletion.

"We have a very different lake from the one that we expected when we entered into the agreement," he said.

The city's part of the agreement calls for them to keep the parks mowed, provide law enforcement for public safety and to prohibit the stocking of any fish other than those the Conservation Department stocks.

As part of that agreement, the Conservation Department removed the fish from Radio Springs Lake before it was drained and donated those fish to a local food pantry.

Before the lake was refilled, the Conservation Department placed fish habitat structures in the lake, worked to get desirable plants in the lake and stocked the lake with fish.

Priesendorf told the board that on April 1, 2006, when the grand opening was held at Radio Springs Lake allowing fishing -- which had been prohibited during the lengthy rehabilitation of the lake habitat -- there was only a negligible amount of aquatic vegetation in the lake.

"By the summer of 2006 the city was treating the lake for Eurasian Aquatic Milfoil," he said, adding that this is an invasive, non-native plant.

Last year he said that the Conservation Department made a new agreement with the city in an effort to control the Eurasian Aquatic Milfoil in the lake.

The lake has been treated unsuccessfully with chemicals several times to kill the plants.

Priesendorf said that the Conservation Department has recently stocked Radio Springs with 40 grass carp to eat the grass, but it will take about two years for them to bring the grass under control.

In the meantime the city and the Conservation Department are looking for ways to bring the goose population under control.

"I really hope we can get control of the goose problem at both lakes, especially at Radio Springs," he said.

As part of that effort the city council enacted an ordinance prohibiting feeding the geese and the Conservation Department asked the parks department to leave a vegetative border around the lakes to discourage the geese.

"The geese are winning," he said.

Priesendorf said that there are several more things that can be tried to solve the problem.

One would involve spreading a chemical around the lake shore that is an irritant to the geese.

He said the chemical will not harm people. In fact, it is the grape flavoring in grape soda. The substance will leave a grape odor around the lake that some people may not like.

The other options involve dispersing the geese using pyrotechnics, which he said might work on Radio Springs because it is fairly small.

If that does not work he said it might come down to "literally taking a small boat and chasing them off.