Notes: Municipal and Industrial (M&I) includes public supply, self-supplied residential, self-supplied industrial, mining, and self-supplied commercial (self-supplied commercial was not calculated in 2000–2010). Agriculture includes aquaculture (1985–2010 only), livestock, and irrigation. Between 1900 and 1945, the M&I category includes water for livestock and dairy.
Sources: Data for 1900–1945 from the Council on Environmental Quality (CEQ) (1991). Data for 1950–2010 from USGS (2014a). Population data from Williamson (2015).
From News Deeply (Padma Nagappan):
Water use has not gone up as population increased in the last few years, contrary to popular opinion and expectations. How does this impact how urban water managers are planning?
UNTIL 1980, WATER use went up steadily as population increased, necessitating investments in infrastructure and boosts to capacity. But since then, there has been a dramatic decoupling across the United States, with water use declining even as the population and the economy continued to grow.
The U.S. Geological Survey found that water consumption peaked at 440 billion gallons (1,665 billion liters) per day before dropping in 1980 and then remained steady through the 1980s and 1990s. It rose slightly in 2000, but significantly declined between 2005 and 2010, when it fell to 350 billion gallons (1,325 billion liters) per day. The USGS attributes this decline to better cooling methods that cut water use for thermoelectric power, and water use efficiencies in irrigation for farming, improved standards for many appliances and fixtures and laws requiring low-flow fixtures.
“Back in 1980 toilets used 6 gallons [23 liters] per flush, but now it’s 1.2 gallons [4.5 liters] in California. These standards have allowed our economies to grow while our communities grew too,” says Heather Cooley, director of the Water Program at the Pacific Institute. “Another reason is the passage of the Clean Water Act, which tried to reduce impacts of waste discharge, that drove efficiency improvements in industry.”
But despite the public and industry adopting efficiency practices, most of us continue to think water use will keep increasing as population grows, so water agencies have planned for it.
“Emphasis has been on building more supply to meet increasing demand. But if water use remains stagnant, that might mean we invest in facilities we ultimately don’t need, or pay for supplies we don’t need,” Cooley points out.
Improve Demand Forecasting
These developments, and the USGS data that showed declines across the board, prompted Cooley and her colleagues to study these trends and put together a community guide for evaluating future urban water demand.
After examining water use data and water agencies’ urban water plans, Cooley and her colleagues found that while water use stayed stagnant or declined in some areas, many utilities were projecting increased water use in the future, which shows they’re not allowing for efficiency improvements and so they could be overestimating demand, which could increase costs for rate payers for water they may not use.
“So we need to improve demand forecasting approaches,” Cooley says. “None of us has a crystal ball, but we can look at trends for the last 20 to 30 years, and use that to calculate water needs, which will help us to develop a much more sustainable water future for California.”
Part of that forecasting is planning for climate change and its impact on demand, something that she says many water agencies have yet to incorporate successfully.
For each area, water forecasting can look very different depending on local variables.