But returning to “Hollywood” showers will just make things worse
You installed a low-flow toilet. You take fast showers. Your yard is water-wise and drought-tolerant. And even if everyone in California were just like you, which they’re not — yet — the state would still see a significant bump in urban water demand by the end of the century. The culprit: warmer temperatures caused by climate change.
An innovative new model developed by researchers at Oakland’s Pacific Institute shows that even if California meets its current goal of reducing per-capita water usage 20 percent by 2020 — and continues to improve water efficiency at a similar rate through the end of the century — still, by 2100 the state’s urban water demand will increase by eight percent, or roughly one million acre-feet (with all other factors held constant). That’s a lot of water: enough to satisfy the current household needs of 6.7 million Californians.
The result came as a surprise even to model co-creator Juliet Christian-Smith. “Warming overwhelms the efficiency improvements,” she said. Here’s why, in a nutshell: warmer temperatures lead to higher evaporation and respiration from plants. It may sound trivial, but it’s serious stuff. Up to half of California’s urban water use takes place outdoors, including at golf courses, parks, and other large landscaped areas. As temperatures increase, it takes more water to hydrate the same plants. (The one million acre-feet figure is based on temperatures associated with a medium-high greenhouse gas emissions scenario.)
It’s also worth noting that at a certain point — around 2080, Christian-Smith projects — the residential efficiency measures that Californians have been slowly adopting since the 1980s will cease being quite as effective. By the end of this century, if we stay on track, enough homes will have low-flow toilets, shower heads, faucets, washing machines, and dishwashers that their benefit will become less pronounced. At that point (what you might call the “saturation point”), we’ll really need to focus on reducing outdoor water use through low-water landscapes and widespread use of reclaimed water.
The Pacific Institute’s new model isn’t just designed to offer another spin on global-warming doom and gloom — or to pooh-pooh your new toilet. Rather, it’s designed to offer a useful tool to water agencies hoping to plan for the future. It’s particularly targeted toward cities and local agencies that lack the ability to develop their own models, Christian-Smith said.
“This tool will allow smaller agencies that don’t have any modeling staff to run some scenarios and potentially include those in their water management plan,” she noted. It’s even available for free to armchair hydrologists. You can download it and an accompanying report, which explains how the model was created and examines a series of six state-level scenarios, at the Pacific Institute’s website.