The city of Waukesha must find a new source of water because the drawdown of the deep aquifer has led to levels of radium above federal standards. Other water quality problems, such as increased salinity and water temperature, have also occurred and will worsen.

Waukesha's water supply options include Lake Michigan surface water to the east or shallow aquifer water to the west.

The city's current water supply is a deep groundwater aquifer that is tributary to Lake Michigan. In other words, Waukesha is currently using water that is part of the Lake Michigan water basin.

This fact comes as a surprise to many people, who have heard that the subcontinental divide is located to the east, between Waukesha and Milwaukee. But the subcontinental divide only determines which direction water on the surface -- such as rain or snowmelt flows.

Surface water to the east of the divide flows toward Lake Michigan. Surface water to the west of the divide flows toward the Mississippi River. The divide in the shallow groundwater aquifer is similar to that on the surface.

On the other hand, the divide in the deep aquifer -- Waukesha's current water source -- is actually west of Waukesha, near the Waukesha County border. The water below Waukesha is tributary to, or flowing toward, Lake Michigan, not the Mississippi.

The deep groundwater is separated from the shallow aquifer by a confining layer of stone above the deep aquifer, called Maquoketa shale. It extends to 20 miles west of Lake Michigan. This geological quirk means that the deep aquifer below Waukesha is not recharged by the shallow or surface water above it. The recharge instead comes from just west of the shale layer. The recharge water and the deep groundwater flow from east to west, below and even into Lake Michigan, except where interrupted by municipal and other deep aquifer wells.

This shale layer is a substantial factor in Waukesha's water supply problems. Because of the stone layer, the deep aquifer in the region is not recharged by rain and snowmelt as quickly as groundwater in other areas. This fact, along with regional water use, has caused the major cone of depression, or drawdown, of the deep aquifer.

Communities throughout southeastern Wisconsin and northeastern Illinois have historically gotten their water from the deep aquifer. Milwaukee, for instance, used the same deep aquifer as Waukesha. Milwaukee switched from the deep aquifer to Lake Michigan surface water when the drawdown reached 325 feet. Today, it is more than 600 feet.

The drawdown in Illinois was even larger. However, under a consent decree issued by the U.S. Supreme Court, Chicago suburbs are switching from Lake Michigan groundwater to Lake Michigan surface water. In 1980, Illinois, Wisconsin, Michigan and others agreed to a policy of using surface water to replace groundwater withdrawals in Illinois. The modification to the consent decree says, "to the extent practicable allocations to new users of Lake Michigan water shall be made with the goal of reducing withdrawals from the Cambrian-Ordovician aquifer."

This policy only applies to Illinois, not to Wisconsin communities like Waukesha. But the aquifer the court and the states seek to protect from drawdown is the same aquifer used by Waukesha and other southeastern Wisconsin communities. In areas of Illinois where communities have switched to surface water, the aquifer had recovered by more than 250 feet between 1980 and 2002. A major cone of depression observed in Elmhurst in 1991 has disappeared. Areas near Chicago have also seen significant aquifer level recoveries.

The good news is that the deep aquifer in Wisconsin can also quickly recover if communities stop or reduce their pumping of it. The U.S. Geological Survey says the water would recover to 50 percent within 7 years and 90 percent in 70 years if pumping is stopped. Recovery of the deep aquifer would reduce negative impacts on surface streams and wetlands in the region.

But no matter what the future source of water will be for Waukesha, regional water sources must be conserved, protected, restored and improved. The Waukesha Water Utility has taken a leadership role by implementing a landmark integrated water resource plan to meet those goals. (See http://www.ci.waukesha.wi.us/WaterUtility/index.html for more information.) For instance, the city will:

• Use water conservation to reduce per capita water use by 20% by 2020.

• Review planning and zoning ordinances to require new developments to have no impact on the natural water cycle.

• Work with Waukesha County and its communities to create a plan to protect sources of drinking water from pollution.

• Adopt storm water best management practices to ensure that rainfall replenishes groundwater supplies that provide public drinking water supplies and support the environment.

Reductions in water use will be accomplished through a combination of public education, new regulations and possible incentives. Education campaigns will help show customers how to save water and money. For instance, the "Don't Flush Dollar$ Down the Drain" campaign shows how a family of four can save $75 to $200 per year by replacing pre-1994 toilets.

Waukesha has also adopted a new sprinkling ordinance that limits watering to two days per week and bans it between 9 a.m. and 5 p.m., when water most easily evaporates.

Waukesha is working with other communities, Waukesha County and Milwaukee County to implement many of these initiatives on a regional scale, to have the greatest impact. Continued leadership and cooperation will assure that regional water problems are addressed effectively, responsibly and affordably to assure safe and sufficient water supplies now and in the future. Meeting those goals will help ensure the economic and environmental health of Wisconsin.

Dan Duchniak is general manager of the Waukesha Water Utility.