Recycling water is good, but we don’t recycle enough of it. Or rather, we don’t have enough uses for recycled water. It’s one thing to reuse gray water from your washing machine and repurpose it to flush the toilet, but what about using it for landscape irrigation or watering city trees?
That’s the recommendation of a team from UCLA, which carried out a study to compare different ways to conserve water in thirsty California. The options were a) to ban the watering of landscapes, such as city parks and trees, or b) to increase the use of recycled water in such cases. The surprise result is that expanding the use of recycled water won out, even beating other alternative water sources.
According to the study, around 20% of the energy used in California goes towards treating, heating, and moving water, which includes pumping it into homes and commercial premises. Then, 52% of California’s water is used for watering crops and irrigating green spaces. While some of the state already uses recycled water for this irrigation, it’s a small proportion of the total.
By switching to recycled water, Californian cities could continue to irrigate green spaces, even as climate change causes more pressure on the water supply. This in turn has benefits to the health of people in the city, allowing them to enjoy green spaces. If you read Co.Exist regularly, you’ll know how good green city spaces are for us–living near tress makes us feel seven years younger, for example, and trees also filter storm water, and suck pollution from the air.
The team also compared using recycled water to other alternative water sources. Desalination proved the most unworkable, using 50% more energy than importing water, and 120 times more energy than just sucking it from the Los Angeles Aqueduct.
Recycling more water and expanding its uses does have an energy cost, but it still wins compared to the inefficient competition.
“Of the conservation strategies we evaluated,” the study’s lead author Sharona Sokolow told the UCLA News Room, “the expanded use of recycled water had the greatest potential to reduce water and energy use and reduce greenhouse gas emissions.”