The City of Waukesha's water use declined for the fifth consecutive year in 2010 to an average daily demand of 6.69 million gallons a day, records show.
Actual demand was 1.21 million gallons a day less than the 2010 estimate included in the city's request for Great Lakes water.
The higher estimate, provided by a consultant in mid-2009, was based on projections of increasing water use on several fronts that didn't come to pass, said Nancy Quirk, technical services manager for the Waukesha Water Utility.
A wet summer in 2010 marked by flooding throughout the region dampened the need for lawn sprinkling while a weak economy stymied forecasts of a surge in industrial and commercial water use and stalled construction of new residential subdivisions, Quirk said.
But significantly lower water use than estimated in 2010, just one year into the city's projections for future water needs, shows why the state Department of Natural Resources must scrutinize each assumption in Waukesha's application, said Eric Ebersberger, the DNR's water use section chief.
"We're questioning everything at this point," he said. Two key questions are how the city's projected water needs 20 and 40 years down the road were determined and if those volumes should be lowered, according to Ebersberger.
Less future demand would reduce the volume of Lake Michigan water diverted to Waukesha, if the application is approved.
In May 2010, Waukesha asked Wisconsin to approve a request to purchase up to an average of 10.9 million gallons a day of Lake Michigan water. If the request is approved by Wisconsin and each of the other seven Great Lakes states, the city would abandon deep wells drawing radium-contaminated water from saturated sandstone.
The application projected water demand starting at an average of 7.9 million gallons a day in 2010, rising to 9.9 mgd in 2030 and 10.9 mgd at mid-century.
All of the city's future water use estimates, and the assumptions used to create them, will be scrutinized by the department in its review of the request, Ebersberger said.
"We'll compare the 2010 projection of 7.9 mgd to actual usage," he said. The basic assumptions -- such as population growth, changes in land use, firefighting needs, water lost to main breaks -- that built the 2010 estimate were used in setting future needs.
The DNR will come up with its own projections of the city's future water needs "and then consider what volume could be saved with conservation measures," Ebersberger said.
The DNR began its review of Waukesha's request last month and is not expected to release its preliminary decision until November. The department could reject the request if it decides Waukesha has adequate local sources of water to meet its needs through mid-century, or it could pass the request on to the other Great Lakes states.
For information on the city's request and the DNR's review, go to the department's website:
http://dnr.wi.gov/org/water/dwg/WaukeshaDiversionApp.htm.
Waukesha pumped an average of 7.78 million gallons a day from its wells in 2005, records show.
A city-wide water conservation ordinance was enacted in 2006 and daily demand that year dropped to an average of 7.18 million gallons, a decrease of 7.7%.
The centerpiece of the conservation ordinance is a May 1 to Oct. 1 ban on lawn sprinkling between 9 a.m and 5 p.m. daily. Customers are allowed to irrigate lawns, flowers, shrubs and trees two days a week, depending on address, but only in early morning or evening.
The city's water use declined slightly in 2007, to an average daily demand of 7.17 million gallons, according to well pumping records.
Demand dropped to an average of 6.9 million gallons a day in 2008, 6.79 million gallons a day in 2009 and 6.69 million gallons a day in 2010.
This summer's hot weather might boost demand in 2011, however.
Water use is rising slightly through mid-August of this year, with average daily pumping up 5% from a year ago, Quirk said.