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One of my favorite depictions of the California drought in popular culture comes from Hilary Duff in A Cinderella Story. “Waiting for you is like waiting for rain in this drought – useless and disappointing” [1]. While this movie was released in 2004, this sentiment remains true 18 years later.
The past 22 years have been ranked as the driest period in the American West dating back 1,200 years. Within this time, California experienced recurring periods of droughts, from 2000-2003, 2007-2009, 2012-2016, and finally, 2020 to present [2]. Dry periods exacerbate the pressures on an already fragile water resource system. To give context on the state’s water resources: 75 percent of the rain and snow in the state falls in the northern third of the state while 80 percent of its water demand lies in the southern two-thirds of the state [3]. Water demands in Central and Southern California are satisfied through inter-basin water transfer systems, diverting water from sources in Northern California and the Colorado River Basin. Major cities in Southern California, such as Los Angeles and San Diego, are heavily reliant on imported water sources, importing 85 percent of their supplies [4,5]. As these inter-basin systems are reliant on rain and snowmelt, drought conditions ripple across water systems.
When surface water supplies dwindle in times of drought, water systems may turn to other water supplies, such as groundwater, stormwater, and recycled water, to fulfill demands. Growing up in California, I was familiar with visibly receding reservoir levels in drought years, but I was oblivious to the hidden water resources utilized around me until I studied and worked in water resources and environmental engineering. Below, I’ll describe how groundwater management plans, green stormwater infrastructure design, and purple recycled water networks are actively employed to build drought resilience in California.
Overexploitation of groundwater resources, particularly in the agricultural Central Valley, contributes to land subsidence, or gradual sinking of Earth’s surface from the aquifer compaction associated with groundwater withdrawals. A dramatic example of land subsidence is found in the San Joaquin Valley in California, where one area of land surface sank nearly 30 feet in 75 years [6]. Aquifer compaction is irreversible, permanently reducing the aquifer’s capacity to store groundwater. To mitigate overdraft of groundwater resources in California, the Sustainable Groundwater Management Act (SGMA) was passed in 2014, requiring local agencies in medium and high priority groundwater basins to form groundwater sustainability agencies to develop and implement plans for long-term sustainable groundwater use [7]. As groundwater provides a useful buffer in times of drought, the SGMA seeks to protect this resource by regulating groundwater usage and identifying sources for recharge when possible.
While groundwater reserves are typically replenished through infiltration of rainwater, the increase in impervious pavement, particularly in urban areas, contributes to greater stormwater runoff rather than infiltration. Stormwater can contribute to flooding, mobilize pollutants, and subsequently degrade receiving water bodies. However, green stormwater infrastructure treats stormwater as a resource instead of a nuisance. Many low impact development (LID) and green stormwater infrastructure (GSI) projects aim to reduce runoff, increase infiltration, and improve water quality of receiving water bodies. Stormwater can also be channeled into spreading grounds to recharge local groundwater aquifers. By increasing infiltration, stormwater management strategies can utilize runoff to increase groundwater supplies. (For more information about green stormwater management, feel free to explore this map of GSI projects in Los Angeles County, proposed and implemented through the passage of an impermeable area parcel tax passed in 2018: https://portal.safecleanwaterla.org/scw-reporting/map[8])
If you’ve seen purple pipes around campus or along a road, their color indicates the use of recycled water, treated to a water quality standard satisfactory for landscape irrigation or industrial purposes. Recycled water is a reliable, sustainable, and drought-resilient water source, using the treatment of municipal wastewater to produce water sufficient for beneficial use. Multiple cities in California distribute free recycled water at fill stations for landscape irrigation [10]. Recycled water is also used for indirect potable reuse through replenishing groundwater basins or augmenting surface water reservoirs used for domestic water supply. For example, Los Angeles Department of Water and Power (LADWP) partnered with the Los Angeles Bureau of Sanitation (LASAN) to replenish aquifers with over 3 million gallons of treated wastewater per day [11]. Here, wastewater is treated through a multi-step wastewater treatment process, ozonation for disinfection, and finally, soil aquifer treatment through the groundwater recharge process. Direct potable reuse (DPR), which is not currently employed in California, skips the intermediate aquifer and reservoir buffers, and instead feeds recycled water directly to drinking water treatment plants or even directly to drinking water systems. State regulations on DPR are still under consideration, but DPR could bring more immediate solutions to meet water demands in potentially dire times of drought [12].
Ultimately, waiting for rain in a drought is useless, disappointing, and not an option we can afford. However, groundwater, stormwater, and recycled water, on the other hand, give hope. With inclusive planning and sustainable management, these resources can be utilized together to bolster drought resilience.
Sources:
1. Rossman, Mark. A Cinderella Story. Warner Bros., 2004.
2. Rogers, Paul. “Current Drought Is Worst in 1,200Years in California and the American West, New Study Shows.” The Mercury News,The Mercury News, 15 Feb. 2022, https://bayareane.ws/3hJHmy7
3. State of California. “The California Water System.” Department of Water Resources, https://water.ca.gov/Water-Basics/The-California-Water-System.
4. Los Angeles Department of Water and Power. “L.A.Water Sources in 2021.” Ladwp.com, https://bit.ly/3TGekg3.
5. City of San Diego. “Water Supply.” The City of San Diego, https://bit.ly/3TN7LZe.
6. United States Geological Survey (USGS). “Land Subsidence Active.” Land Subsidence, U.S. Department of the Interior, https://on.doi.gov/3ObhN4Q.
7. State of California. “Sustainable Groundwater Management Act (SGMA).” Department of Water Resources, https://bit.ly/3gfqVca.
8. Safe Clean Water Program. “Safe Clean Water Portal.” SCW Reporting Map, https://portal.safecleanwaterla.org/scw-reporting/map.
9. City of San Luis Obispo. “Recycled Water.” City of San Luis Obispo, CA, https://bit.ly/3g8pXOZ.
10. Hansen, Nick. “How to Get Free Recycled Water in California.” Water, News Deeply, 25 Aug. 2016, https://bit.ly/3tz2YQa.
11. Los Angeles Department of Water and Power.“Groundwater Replenishment.” Ladwp.com, https://bit.ly/3g6vsO7
12. California State Water Resources Control Board.“Regulating Direct Potable Reuse in California.” SWRCB.gov, https://bit.ly/3tvieO4.