"From 2002 to 2012, from those top twelve customers, a twelve-percent in overall water use. About a million gallons," said Nancy Quirk, General Manager of the Green Bay Water Utility.

And a Department of Natural Resources study finds new efficiencies must continue. The study found in 2011 that just over two-trillion gallons of water was drawn from various sources. 76-percent was used for power generation. W-P-S says most of the water used by generating plants goes right back where it comes from, after being treated and cooled.

"We take it from the Fox River, for example with the Pulliam, we use it to cool some of the water that we get from the City of Green Bay, which we use to generate electricity, and then it goes back into the bay," said Kerry Spees, WPS spokesman.

Utilities try to lead by example to make water usage more efficient. That means adopting new technologies whenever possible.

"The Fox Energy Center in Kaukauna that uses waste water from a treatment facility. We're probably going to see more things like that," Spees said.

"We have replaced all of our pumps within the last two years to the more efficient pumps, variable speed drives that gives us more energy efficiency, which in turn reduce our costs," said Quirk.