With the ever-changing climate and increasingly dry summers, California faces water challenges, despite this year’s bountiful snowpack. At the February meeting of the California Water Commission, Heather Cooley, Director of Research at the Pacific Institute, explained how increasing water efficiency, water reuse, and stormwater capture is essential to building and enhancing California’s water resilience.
Heather Cooley began by noting that the past 22 years in the southwestern US have been the driest in 1200 years, partly due to climate change. However, there is a growing recognition it’s more than a drought; it’s a fundamental shift in our climate to one that is hotter and drier and will include longer, more intense droughts requiring us to change how we use and manage water.
What is water resilience?
Water resilience is a term frequently used in the water community, but what does it mean? Ms. Cooley said the term emerged in response to climate change but is now recognized to include a broader range of shocks and stresses on our water systems and communities.
“The Pacific Institute came together to try to define what that term meant, as there are a lot of definitions out there,” she said. “What we landed on is that water resilience is the ability of water systems to function so that nature and people, including those on the frontlines and disproportionally impacted, thrive under shock, stresses, and change. Our efforts around water resilience must build on a foundation of water sustainability and security so that we do not lose the lessons of water sustainability and the need to balance social, economic, and environmental needs. We need to think about not only our needs today but future generations. We must integrate these concepts to help our communities thrive under these new conditions.”
Three fundamental shifts are needed
There are three fundamental shifts needed to enhance water resilience:
Rethinking water demand
Ms. Cooley said we must shift away from a notion of an abundance of water and dramatically expand efforts to reduce waste and inefficiency across all sectors. We must also rethink our economic priorities and choices. In urban areas, this includes replacing old appliances and fixtures with newer, water-efficient models, drought-tolerant and low water use landscapes, denser developments, and fixing leaks in water delivery systems. She noted that new technologies are available to help homes and businesses do that.
As a large water user, agriculture must also play a role, she said. Increasingly, farmers are installing more efficient irrigation systems, improving soil health, switching to less water intensive crops, and even fallowing land in some instances.
Rethinking water supply
We must also rethink our supply, moving away from reliance on over-tapped surface and groundwater aquifers and looking to new sources of supply. This can include recycling and reusing water, capturing urban runoff, and some forms of desalination.
The building on the slide is a high-rise residential building in San Francisco that uses grey water and rainwater for toilet flushing and irrigation. These types of systems are now required in San Francisco in new developments and major redevelopments of 100,000 square feet and more.
“There’s a lot of exciting innovation happening, and that’s one example,” she said.
Rethinking water management
We must also rethink how we manage water. Ms. Cooley said that we need to shift from a siloed approach where water, wastewater, and stormwater are managed separately and where water and land use planning are disconnected and embrace a more integrated approach. We must expand our definition of infrastructure to include our watersheds, upland forest, and downstream wetlands in a much more integrated and holistic fashion. We must embrace new technologies that enable us to get more real-time data that we can then use to make better choices.
Trends and opportunities to do more
There is a widespread misconception that as California grows, so will water demand, but Ms. Cooley pointed out that California has experienced a dramatic decoupling of water use and growth over the past 40 years. The figure on the slide shows water use, population, and gross state product indexed to 1967 numbers.
“What it shows is that before 1980, water usage and population were growing at about the same rate,” she said. “But beginning around 1980, there was an important shift; water use began to stabilize, whereas the population and the economy continued to grow. So over this 50-year period, we’ve seen that the gross state product has increased by a factor of five, the population has doubled, but water use has increased by just 13%. This is a really important point we need to broadly recognize and acknowledge. We need to think about how to do more of this because I believe there are more opportunities.”
This decoupling is due to several factors, including the greater use of water-efficient devices in agriculture and urban areas, more climate-appropriate plants, denser developments that reduce outdoor irrigation, and structural changes in the economy, moving from a manufacturing water-intensive economy to a less water-intensive, service-oriented economy. It’s also due to significant increases in the development of local water supplies, such as recycled water use and stormwater capture.
Southern California exemplifies this shift, having made tangible progress in advancing water efficiency and developing local water sources. The slide shows water usage and the breakdown of the different water sources.
“Water use across the Metropolitan Water District service area in 2020 was about the same level as it was in the mid-1970s, despite significant population and economic growth,” said Ms. Cooley. “The region has also increased its use of recycled water and other local water sources. And together, these strategies have reduced reliance on increasingly variable and uncertain sources of imported water. And importantly, without these efforts, the region’s water supply challenges would be much worse.”
Pacific Institute Report: The Untapped Potential of California’s Urban Water Supply: Water Efficiency, Water Reuse, and Stormwater Capture
Last April, the Pacific Institute released the report, The Untapped Potential of California’s Urban Water Supply: Water Efficiency, Water Reuse, and Stormwater Capture, which analyzed the potential of increasing urban water efficiency, water reuse, and stormwater capture.
The report is a snapshot of the opportunities using existing technologies and practices. As new technologies and practices become available and the population grows, the numbers could change.
The state has made significant progress in water efficiency. However, if all California homes were equipped with the same water-efficient appliances and fixtures required of new homes, if businesses were more efficient with their use, and if all urban landscapes met the requirements of the state’s model landscape ordinances, urban water use could be reduced about 30% or 1.8 million acre-feet. Furthermore, that number could be reduced up to 48% of 2.1 million acre-feet by using fixtures and devices currently available that are more efficient than the current standards.
Similarly, the state has made much progress with water recycling, currently recycling about 25% of municipal wastewater. However, the report estimates that an additional 1.8 to 2.1 million acre-feet of municipal wastewater is available for reuse that is currently discharged to land, ocean, or inland waters that is not reserved for instream flows.
With urban stormwater capture, there isn’t a good way to estimate what is currently being captured. So the researchers evaluated how much precipitation was falling on impervious surfaces, particularly in areas overlying groundwater aquifers. Using this method, they estimate between 580,000 acre-feet in a dry year and up to 3 million acre-feet in a wet year is potentially available for capture.
Investment is needed
“Of course, this isn’t going to happen naturally,” said Ms. Cooley. “A lot of investments will be needed. What these studies though demonstrate is there are significant opportunities that remain in the areas of urban efficiency, water reuse, and stormwater capture.”
“Importantly, I want to emphasize that these strategies, in particular, not only provide water supply benefits, they can provide other important co-benefits,” she continued. “Stormwater capture, as we’ve just heard, can also reduce flood risk, improve water quality, and enhance the environment and community livability. Water efficiency not only reduces water use, but it reduces water-related energy use as well as greenhouse gas emissions. So it can help us meet not only our water goals, but our energy and greenhouse gas goals as well.”
In conclusion …
“Finally, I’d like to conclude by reiterating that climate change is really requiring us to fundamentally change how we use and manage water. We must embrace resilience, prioritize water conservation and efficiency to reduce water demand, diversify our water supplies through water reuse and stormwater capture, and shift to a more integrated management that values green infrastructure and relies on better data and planning.”
