Although water, especially fresh water, is becoming an increasingly scarce commodity around the world, here in Michigan, we are indeed fortunate to have an abundance of water resources, both surface water and groundwater.

We all benefit from the many ways we use this water -- and lots of it -- and much of our economy is tied to our water wealth.

But with the consequences of global climate change only poorly understood, it's no wonder that some folks have gotten a little "testy" about corporations bottling and selling "our" water.

Happily, there is no overall shortage of water in this state.

Surrounded by four of the five Great Lakes, most Michiganians are well aware of the vast surface water that covers more than 40,000 square miles of Michigan's total land and water area.

But many may be unfamiliar with the equally important water resources found below ground. According to recent estimates, groundwater supplies 23% of our total water needs and is the public water supply for half our state's residents.

That's why these water resources, as abundant as they appear during cool April showers, need thoughtful management to protect aquatic ecosystems, avoid user conflicts, and ensure sustainable water uses into the future.

Beginning in 2003, the Michigan Legislature took action to protect our water resources from overuse by passing a series of bills. The first, Public Act 148, established the Groundwater Conservation Advisory Council and created a statewide groundwater inventory and mapping project, the results of which can be accessed at http://gwmap.rsgis.msu.edu/. Public Act 177 of 2003 then established a new process for the Department of Environmentally Quality to review and mediate groundwater disputes between users, a process that previously needed to be resolved through the court.

The Groundwater Conservation Advisory Council is comprised of members appointed from business and manufacturing interests, utilities, agricultural representatives, conservation and environmental organizations, and local and state governments.

The Department of Natural Resources helps administer the council, and is represented by co-chair Dr. Paul Seelbach, who is statewide research manager for the DNR Fisheries Division.

"One of the council's mandates was to study the sustainability of the state's groundwater use and whether the state should provide additional oversight of groundwater withdrawals," Seelbach explained. "Certain groundwater sources can support fairly large withdrawals without harm to the ecosystem or to other users. Other groundwater sources are more sensitive to large withdrawals."

In February 2006, the council published a report to the Legislature, which provided information on groundwater resources and development in Michigan, and included recommendations for next steps toward improved groundwater resource assessment and management.

"The council recognized the amount of groundwater withdrawn from any aquifer must be sustainable," Seelbach said. "Our findings indicated some areas of the state are more sensitive to groundwater withdrawal than others. Current and future withdrawals in these sensitive areas will require a higher degree of monitoring, scientific research and understanding."

In 2006, the Legislature then amended Parts 327 and 328 of the Natural Resources and Environmental Protection Act to address water-use registration, reporting, environmental protection standards for water users and requirements for new "large quantity withdrawals" from groundwater and surface water.

According to the statute, a large quantity withdrawal is a withdrawal greater than 100,000 gallons per day averaged over a consecutive 30-day period. The law allows users who are bottling water for resale to pump up to 250,000 gallons per day without a state permit, provided the well is at least 1,300 feet from the nearest surface water. All other users don't need a permit until they are proposing a new withdrawal of two million gallons per day.

To put this in perspective, Michigan pumps 730 million gallons of groundwater per day, according to the most recent estimates available.

Another important aspect of the law is that no new large quantity withdrawal is allowed that would cause a significant adverse resource impact to the characteristic fish population in the affected streams and lakes.

To help determine the effects of a withdrawal, the council is developing a water withdrawal assessment tool that includes what is known about groundwater amounts and movements, stream flows, and habitat needs for fishes across Michigan.

"This tool will assist new users in assessing whether their proposed large quantity withdrawal is likely to cause an adverse effect to local aquatic resources, prior to implementing the withdrawal," said Seelbach.

Just as the streams and rivers of the Great Lakes basin feed the Great Lakes themselves, groundwater aquifers feed water to streams.

In fact, stream flow during the summer low flow period (typically August or September) is nearly all groundwater. This is commonly referred to the "base flow" of a stream. Because the summer low flow period is when aquatic invertebrates and fishes are the most vulnerable to water loss, the natural resource impact assessment for new groundwater withdrawal focuses on the stream's base flow condition.

DNR fisheries managers are concerned that groundwater withdrawn from a location that interrupts water that normally would find its way to a local stream could change the base flow and temperature of the stream enough that the characteristic fish population would be altered.

Research conducted by the DNR and the University of Michigan has determined which fish species might be expected to occur in a given stream based on the relative contribution of groundwater to stream flow, the water temperature, and the size of the stream's contributing watershed or catchment area.

At present, the law prohibits an adverse resource impact only to trout streams until the water withdrawal assessment tool is complete and further action is considered by the Legislature.

After February 2008, an adverse resource impact from a new large quantity withdrawal (as measured by a change in the characteristic fish population) will be prohibited in any stream or lake.

"This is huge step forward, unique in the country," Seelbach said. "Groundwater sustainability involves balancing the demands placed on the resource by the economic, social and environmental sectors, ensuring the needs of current and future generations are not compromised by current usage. The resource should be managed on well-founded scientific analysis."

The council is expected to complete its work by mid-summer and will be providing a report and further recommendations to the Legislature.