In 2014 California enacted the Sustainable Groundwater Management Act, which provides the framework for local water management agencies to develop and implement groundwater sustainability plans in order to sustainably manage the state's groundwater within 20 years. This legislation was California's first ever attempt to sustainably manage groundwater resources, a long overdue effort given that the state relies on groundwater for 40 percent of its total water supply in an average year. The Sustainable Groundwater Management Act aims to ensure that groundwater basins are being managed in a way that achieves "sustainable yield"—the maximum quantity of water that can be withdrawn annually from a groundwater supply without causing an "undesirable result."
The same year that the Sustainable Groundwater Management Act passed, the California State Water Boards were required to adopt regulations for groundwater replenishment using recycled water. Around this same time, California also updated its water recycling policy, emphasizing the need to shift away from disproportionate reliance on large-scale regional water supply systems—namely, the State Water Project and Central Valley Projects running through the Sacramento Bay-Delta and the Colorado River—and towards more diversified local supplies. The amended policy acknowledged that the "collapse of the Bay-Delta ecosystem, climate change, and continuing population growth have combined with a severe drought on the Colorado River and failing levees in the Delta to create a new reality that challenges California's ability to provide the clean water needed for a healthy environment, a healthy population and a healthy economy, both now and in the future."
To alleviate existential threats to its major water supply systems, California's Recycled Water Policy mandated the State Water Boards to "exercise the authority granted to them by the Legislature to the fullest extent possible to encourage the use of recycled water, consistent with state and federal water quality laws." Thus, the State Boards "strongly encourage local and regional water agencies to move toward clean, abundant, local water for California by emphasizing appropriate water recycling, water conservation, and maintenance of supply infrastructure and the use of storm water (including dry-weather urban runoff)" in an effort to diversify water supply portfolios statewide.
Today, diversification of water supplies to include local, recycled sources has moved up the ladder of priorities for major municipal water managers. For example, Metropolitan Water District (MWD), Southern California's regional water supplier, and the largest water wholesaler in the world, is actively examining large-scale investments in recycled water from water treatment plants. A comparison between MWD's past and future water supply portfolio is illustrative of the direction of California's water future. In 1990, imported water from the Sacramento Bay-Delta and Colorado River systems provided some 59% of MWD's water supply, and water conservation and recycling accounted for a mere 7% of supply. Now, MWD is projecting its 2035 water supply portfolio to consist of 36% imported water and 33% conserved and recycled water. This projected seismic shift indicates just how aggressively MWD, in recognition of system wide vulnerabilities caused by an array of issues that are outside the scope of this discussion (i.e. drought, population growth, climate change), intends to develop more local and resilient water supplies. That trend is also manifesting in the activities of other large municipal water management agencies throughout California.
The Orange County Water District (OCWD) is a special district responsible for managing the Orange County Groundwater Basin. It has bought imported water from MWD for decades, but, recognizing the need for greater self-reliance constructed and began operating a groundwater replenishment system in 2008 that currently produces approximately 100 million gallons of purified water each day that can be recharged into the local aquifer. OCWD has already constructed one expansion of this system, and in August, 2018 it received a $135 million federal grant to "purify treated wastewater from the Orange County Sanitation District to produce an additional 30 million gallons per day of drinking water, which will be stored in the Orange County Groundwater Basin." In Northern California, Santa Clara Valley Water District (SCVWD) has plans to "provide up to 45,000 acre-feet per year (AFY) of purified water for indirect and/or direct potable reuse to supplement groundwater recharge from other existing sources, such as imported and locally-stored water supply." SCVWD's 2012 Master Plan provided that "at least 20,000 AFY of advanced treated recycled water will be available for groundwater recharge by 2030."
Four years into California's first-ever effort to manage groundwater supplies, it is clear that California water managers are looking for creative strategies that give them flexibility to manage their water supply portfolios and navigate threats to large imported water systems under increasing stress. In order for a state that has never had any meaningful groundwater regulation to achieve sustainable yield in its groundwater basins in the 20-year period allotted by the Sustainable Groundwater Management Act continued development of localized sources is likely.
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