Barnes told the group, who had boarded a bus at the Marion County Courthouse to view soil retaining efforts around the lake, that the data collected from an automatic sampler on French Creek at the bridge on Indigo Road indicated enough pollution for lake destruction.
The data indicate that potentially toxic infestations of blue-green algae probably will occur into the forseeable future, the various guides to the Marion County Surface Water Advisory Board tour warned.
Barnes’ measurements for that rainy day indicated the swollen French Creek carried 4,400 tons of sediment, 48 tons of nitrogen and 15 tons of phosphorus into the reservoir.
He said heat, combined with nutrients, increase the growth of algae and the eutrophication of the lake. Storms plus wave action break up the materials and algae growth, and help clean the lake.
Even though it may seem that the wind blows a lot in this area, Barnes said unfortunately for this situation, Marion Reservoir is in one of the lower-wind occurence areas of the state.
This means wind and wave action have less chance of putting oxygen into the water here.
Barnes has seven monitoring sites on the reservoir. One of the others, an automated Isco sampler like the French Creek one only located on the Cottonwood River west of Durham, had to be relocated because of excessive log jamming.
The other five sites are at the outflow below the reservoir: at Marion Cove, at Hillsboro Cove, on Silver Creek at Kansas Highway 15, and on the bridge on Kanza Road.
Barnes is placing pins to measure streambank erosion, although he said riparian vegetation buffers along the streams appear to provide excellent control.
His efforts are being supplemented beginning in July by the Kansas Biological Survey taking reservoir core samples to study release of polluting nutrients from sediment.
Elsewhere on the tour, Matt Farmer of the Kansas Department of Wildlife and Parks showed a wetlands area which drains into the reservoir. The drainage is controlled by manual gates in a tube under 250th Road just before it dead ends on the water.
Farmer said large cottonwood trees and willows that dominate the area now are to be removed with help of county equipment.
The goal will be to create a native prairie marshland that will support more wildlife species (900 species estimated), and do a better job of absorbing sediments, nutrients and pollutants, he said.
The area will help erosion and flood control plus enhance ground water recharge, he added.
Gary Schuler of the Natural Resource and Conservation Service in Marion showed tour participants a number of erosion-control practices that slow pollution in the reservoir enroute to Tampa.
His first observation, though, was of an “ephemeral gulley” that, without controls, will continue to be a pollution factor. It was in the middle of a field, and Schuler said it measures 1,100 feet long by 6 feet wide.
During a season, he said, it is estimated that 128 tons of soil deep is washed off the field, which either ends up further down the field or in the reservoir.
The problem is masked, he said, by the farmer tilling up new earth to refill the gulley each year.
Schuller also showed a grass waterway with terraces, which are structures that help halt the problems illustrated by the former stop.
He said Marion County is in one of the highest intensity rainfall areas of the state, with frequent damaging 5- and 6-inch downpours.
Schuler showed another underground tile drainage field that runs water to a grass waterway.
The next area used a concrete control structure emptying into a county ditch where a 30 to 40-foot stream draw had tiles for drainage underground, and a broad border of planted native grasses and wildflowers to promote wildlife.
At a no-till field where crop residues were left with new soybeans, Schuler said the left-over vegetation can break up rain drops capable of the equivalent of 20 tons of TNT striking each point annually.
A final stop was a visit to newly constructed shallow water wetlands alongside crop land that will use erosion controlling native grasses to promote duck habitat.