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Study helps chart course for water usage

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WILLIAMS BAY — Communities around Geneva Lake now are equipped with a tool that can help them understand the impact future development could have on water resources.

The Wisconsin Geological and Natural History Survey has developed a computer model to map groundwater flow, learn how groundwater and surface water are connected and measure the impact of pumping.

The model focuses on Geneva Lake and the communities of Fontana, Lake Geneva and Williams Bay and Linn and Walworth townships.

Those communities are members of the Geneva Lake Environmental Agency, which commissioned the project.

Madeline Gotkowitz, the hydrogeologist who led the yearlong study, said the model shows:

-- Groundwater and surface water are closely connected. Groundwater discharges into streams, rivers and lakes.

-- High-capacity wells "intercept" groundwater that otherwise would discharge into the lake and its tributaries.

-- Pumping has a more significant impact on nearby streams than it does on the lake.

Gotkowitz said the model provides the communities around Geneva Lake with science-based information to help them make smart decisions about managing water resources.

Impacts

The communities around Geneva Lake are concerned about the long-term effects increased pumping could have on the lake and its tributaries, said Ted Peters, executive director of the Geneva Lake Environmental Agency.

A 2006 study showed the 19 largest high-capacity wells in the area are lowering the water table on the west side of the lake, but it didn't address how such changes in groundwater affect surface water.

The model does that, and it shows:

-- Modern conditions, which assumed pumping at 2006 rates, reduce total water flow to the lake by 4 percent compared to predevelopment conditions, which assumed no pumping.

-- Modern conditions reduce discharge to the lake from groundwater and tributaries by 9 percent compared to predevelopment conditions.

-- Modern conditions reduce flow in three tributaries—Gardens, Harris and Potawatomi creeks—by 17, 32 and 35 percent, respectively. Gardens Creek and Potawatomi Creek are at the west end of the lake. Harris Creek is near Williams Bay.

While in general pumping reduces the amount of water flowing through streams, rivers and lakes, pumping must be considered as part of the entire hydrologic cycle, Gotkowitz said.

Wells pump groundwater for residential, commercial and industrial use. After it is used, the water goes through the sanitary sewer system to a wastewater treatment plant, is treated and discharged back into the system.

But not every community pumps and discharges water the same way, Gotkowitz said.

Lake Geneva, for example, pumps water from and discharges water into the White River basin, while Fontana, Walworth and Williams Bay pump water from the Geneva Lake basin and discharge water outside the basin.

Diverting water from the groundwater recharge area means it doesn't return to Geneva Lake, Gotkowitz said. And while that means less water flowing to the lake, it might be done as a practice to improve lake water quality, she said.

Solutions

The communities around Geneva Lake shouldn't assume the model is advocating they stop growing to protect the lake and its tributaries, Gotkowitz said.

"Everybody needs water," she said. "We're not suggesting that no one should pump water."

Instead, the model shows that communities around the lake, particularly those on the west side of the lake, might consider reducing pumping rates at wells near streams to preserve groundwater and restore flow to the lake and its tributaries, Gotkowitz said.

For example, homeowners and businesses, especially those that use a lot of water—golf courses, hotels and hospitals—could make an effort to reduce their consumption, she said.

Peters said the model isn't just facts and figures; it's a tool communities can use to plan for their futures.

"It gives us a better understanding of the groundwater shed for consideration of future land use in those areas," he said.

Gotkowitz said that's exactly the line of thinking that was intended when she set out to do the project a year ago.

"These people love their lake," she said, "and we want them to use the model to understand what's going on using science."