The South Platte Reservoir has the capacity to hold more than 6,400 acre-feet of water and serves as one of the district's major raw water storage sites. Photo: Centennial Water & Sanitation District
A geologist walks through a 1.5 mile tunnel that connects to a series of five collector wells to reach cleaner source water. The project went online in September. Photo: Louisville Water Co.

By Rachel Brand

Over the last quarter century, per-household water consumption has remained level, allowing utility managers to create fairly reliable and accurate plans based on steady population growth. But between the housing boom and the subsequent stagnant economy — in addition to more homeowners installing low-flow appliances — managers can no longer use traditional population growth models to develop long-term plans.

The Water Research Foundation's “North American Residential Water Usage Trends Since 1992” uncovers the reasons for the national decline in water use (see sidebar on page 35) and explains how two disparate communities are making up for the subsequent decrease in revenues.

“Every water utility is different — with unique governance, climate, supplies, and customers,” says Rob Renner, executive director of the foundation, which funds research on behalf of water suppliers. “Although this report focuses on Louisville and Centennial, it points to a problem that utilities across the country are facing.”

About 700,000 people live in Louisville, an average of 2.37 people per household compared to 3.16 per household in 1970. Unlike communities in the West and Southwest, Louisville has abundant supplies. Situated on the Ohio River, the “northernmost city in the South” is located on a wide, flat floodplain surrounded by rolling hills and horse farms.

Louisville Water Co. President Greg Heitzman says the utility had been concerned about declining water use since the Energy Policy Act of 1992, which mandates uniform efficiency standards for toilets, urinals, showerheads, and faucets manufactured after 1994.

Two towns, two challenges

  • Water-rich: Louisville Water Co.
  • No. residential customers: 247,000

    Average monthly consumption, 1990: 6,300 gallons

    Average monthly consumption, 2009: 5,100 gallons

    Annual operating budget: $152 million

  • Water-poor: Centennial (Colo.) Water and Sanitation District
  • No. residential customers: 27,000

    Average monthly consumption, 2001: 11,583 gallons

    Average monthly consumption, 2009: 9,166 gallons

    Annual operating budget: $21 million


    To understand the drop in residential water use, researchers surveyed utility customers, analyzed databases, and placed data loggers on 65 residences.

    “While some utilities were running on hookup charges, there was this trend of declining numbers of people per household and penetration of low-use fixtures,” Paul Coomes, professor of economics at the University of Louisville, says of the regional trend. “So utilities were stuck in this bind of stretching their infrastructure out to the suburbs, forcing them to come up with operating efficiencies while revenues stayed flat.” The recession further pushed down water use.

    In 1990, Louisville Water Co. had 2,800 miles of pipe, 217,000 customers, and sales of 37 billion gallons. Today, 4,600 miles of pipe — a 64% jump — serve 28% more customers. Sales remain flat at 36 billion gallons. “From a purely macroeconomic perspective, it's not an efficient use of capital,” Heitzman says. “We're pumping less water over a larger base of infrastructure. We're moving to a point where the water-sewer bill is more than $100 a month, so we may be seeing individuals installing water-saving devices on their own.”

    This will only exacerbate the utility's predicament.