How better wastewater management can help California adapt to climate change

By Caitrin Chappelle and Henry McCann, Special to CALmatters

Our public health relies on wastewater management to treat sewage and remove pollutants coming from our homes and businesses.

This system is fundamental to protecting our health. In California, treated wastewater also is a critical source of water for the environment, and, increasingly, a source for recycled water. Climate change is worsening water scarcity and flood risks. Advancements in engineering and technology can help prepare wastewater agencies for a changing climate. But significant shifts in policy and planning are needed to address these challenges.

Wastewater agencies must reliably remove pollutants even as the quantity and quality of the water they treat declines during droughts, and when large storms push their equipment to the breaking point.

In February, an atmospheric river storm—the type that is expected to become more common as the climate warms―inundated Healdsburg’s wastewater treatment facility and pushed more than five times the normal flow of wastewater and runoff into Santa Rosa’s treatment plant.

In a drought, reduced flows to wastewater plants can hamper agencies’ ability to comply with treatment standards, damage equipment, increase costs, and shrink revenue. Lower inflows also reduce the volumes available for recycled water, often considered a “drought-proof” supply.

The drought of 2012–16 brought all of these problems to the fore. Many wastewater agencies are now changing their operations, infrastructure, or finances in response to the challenges they experienced. Our new study recommends sector-wide changes in three areas to help build the sector’s climate resilience:

  • Maintain water quality in the face of reduced indoor water use. Short-term water conservation during droughts and longer term reductions in water use from indoor efficiency measures challenge wastewater management. All wastewater agencies should assess their vulnerability to major climate pressures, and plan for future droughts. Better coordination and information sharing with suppliers about indoor water conservation and efficiency efforts are also key.
  • Make smart recycled water investments. Coordination among wastewater and water supply agencies is needed to address the demand for recycled water. Regional planning for recycled water projects can result in investments that are more responsive to changing water use and an increasingly volatile climate, bringing financial and environmental benefits.
  • Balance conflicting objectives within watersheds. Many wastewater treatment plants discharge treated water into inland watersheds.

Meeting increased demand for recycled water may fuel conflict over the use of treated discharge to support ecosystems and downstream users. Rivers and streams are expected to experience lower flows and higher temperatures, which will heighten threats to aquatic ecosystems. Resources are needed to identify areas most at risk of conflict over the use of treated wastewater, and to develop tools to evaluate the impacts of water recycling projects on the environment and downstream water users.  

The state can help wastewater managers make these adaptations, which are critical to building a more integrated and resilient water system. The State Water Board should align its policies on water use, wastewater, recycled water, and environmental protection to better manage for these multiple objectives.

Forging new partnerships to tackle the full range of climate-related risks will help wastewater agencies determine the best adaptations and improvements needed to prepare wastewater management—and California’s water system as a whole—for a more volatile future.


Caitrin Chappelle is associate director of the Public Policy Institute of California’s Water Policy Center, [email protected]. Henry McCann is a research associate, [email protected] They wrote this commentary for CALmatters.

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