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What do we use our water for?

February 21, 2008

Media Contacts:
Dr. Garry Grabow, assistant professor and North Carolina Cooperative Extension Specialist, College of Agriculture and Life Sciences, North Carolina State University, 919.513.7348 or garry_grabow@ncsu.edu
Mitch Woodward, N.C. Cooperative Extension area specialized agent for environmental education, Wake County, 919-250-1112 or mitch_woodward@ncsu.edu
Dr. Diana Rashash, N.C. Cooperative Extension area specialized agent for natural resources/environmental education, Onslow County, 910.455.5873 or diana_rashash@ncsu.edu

An ongoing public discussion about who uses how much water for what seems to grow increasingly heated as North Carolina's drought steadily worsens. But obtaining consistent water-use statistics can be challenging.

Based on a U.S. Geological Survey report, Dr. Garry Grabow, assistant professor and N.C. Cooperative Extension specialist at North Carolina State University, estimates that "industrial, commercial and outdoor household use consume somewhere around 100 gallons per day per person on average across North Carolina for those served by public water supply systems."

However, Grabow adds, the USGS report "addresses only broad sectors, such as irrigation, which mostly means agricultural production, as well as mining and electric power generation, and does not differentiate between indoor and outdoor uses."

When it gets down to figuring out use per household - indoor or outdoor - and commercial uses, the equations get tricky and rely on a combination of personal observation and scientific studies.

Mitch Woodward, N.C. Cooperative Extension area specialized agent for environmental education in Wake County, says the City of Raleigh pumps 40 percent less water on days when outdoor irrigation is prohibited.

He bases his outdoor water use statistics on his research in summer 2000, when a serious drought already was in full force. Woodward says a 5,000-square-foot lawn - about the average size for Cary, N.C. - will use 2,300 gallons per week, or 30,000 gallons over June, July and August.

"Outdoor water use can be highly variable depending upon whether or not you irrigate, and if so, how large your turf area is," says Grabow. "Lawn sizes vary from house-to-house and from town-to-town," and that affects total outdoor water use.

"Folks who drag hoses around probably under-irrigate due to the labor involved. In fact, those with permanent irrigation systems use about double the amount used by folks who drag hoses around," he says.

That's according to a 2004 study by Drs. Deanna Osmond, professor of soil science at N.C. State, and David Hardy, N.C. Department of Agriculture and Consumer Services, Grabow says.

"Outdoor watering accounts for a sizeable amount of total household use," Grabow adds. "But the proportions of outdoor-to-indoor water use vary according to information sources." Various sources put outdoor water use at anywhere from more than 50 percent of total household use to 20 percent, which is the percentage Raleigh officials estimate city residents use.

"Outdoor water use can range from over half of total household water use during peak use months - June, July and August - to nil during the winter months," Grabow says. "When you mix in the fact that some folks don't bother to water lawns and plants, I think the City of Raleigh quote of up to 20 percent of total water consumption is probably not far off."

"Wilmington has calculated it at roughly 22 percent," notes Dr. Diana Rashash, N.C. Cooperative Extension area specialized agent for natural resources/environmental education in Onslow County. "They use 16-to-17 million gallons per day (mgd) during most months and 22-to-23 mgd during the summer."

To parse the numbers as accurately as possible and to introduce a reality check, Grabow, who has both indoor and outdoor water-use meters at his house, checked his water use with the Town of Holly Springs.

"Outdoor usage for our family of four during a peak outdoor use month - June 2007 - was 63 percent of our total water use for an irrigated turf area of about 2,000 square feet plus drip irrigated areas," he says. "Of course now, in February 2008, it is 0 percent of our total water use and will be until May, assuming the drought has eased.

"The Town of Cary," he says, "found that in 2005, almost 50 percent of total water use went towards irrigation for single-family homes with an irrigation meter. The percent ranged from just a few in the winter months to over 60 from July through October. When all customers including multi-family and commercial were considered, irrigation usage was 34 percent of the total water use for those with irrigation meters."

Extension's Woodward takes a shot at an even smaller statistical target, individual household water use.

"Households use an average of 120 gallons indoors per person a day nationwide," he says. "The older toilets and clothes washers are by far the largest indoor water users, using 40 to 60 gallons for a load of clothes for washers less than 20 years old; front loaders use closer to 20 gallons per load. Toilets use from 1.6 to 5 gallons per flush, depending on whether or not you have a low-flush toilet. And a public urinal can use from a half-gallon to a gallon per flush, again depending on how new the technology is."

"Another important water use is showers," says Rashash. "Older showerheads use 6 to 8 gallons per minute. Low-flow, high-pressure showerheads are readily available that use only 2 gallons per minute. They are also very easy to install and cost less than $15."

How does your household water usage compare to households across the nation? Rashash suggests an online water use calculator made available by Orange County, N.C. and borrowed from the University of South Florida. The calculator is at http://www.owasa.org/pages/WaterCalculator.html

Written by: Art Latham, 919.513.3117 or art_latham@ncsu.edu

Posted by Dave at February 21, 2008 08:00 AM