Managing Wastewater in a Changing Climate

Public Policy Institute of California (PPIC) | April 15th, 2019

California’s wastewater sector, which plays a crucial role in protecting publichealth and the environment, is at a turning point. Water supply and demand condit

California’s wastewater sector, which plays a crucial role in protecting publichealth and the environment, is at a turning point. Water supply and demand conditions are being affected by population growth, technology and policy changes, and drought. Climate change will bring new challenges. Wastewater agencies are tasked with reliably removing pollutants from water discarded to sewers, even as the quantity and quality of the water they treat declines. Of the multiple climate pressures that are likely to affect wastewater management, drought poses the biggest challenge for the sector. The unusually hot drought of 2012–16 provided a vivid demonstration of conditions that may become more common as the climate warms, and was a wake-up call for wastewater agencies. Many wastewater agencies are pursuing specific changes to their operations, infrastructure, or finances in response to the cascade of challenges they experienced during the latest drought. A PPIC survey of wastewater agencies done as part of this study found a high degree of concern in the sector about adapting to a changing climate. This report recommends policy and management changes to help build resilience in three broad areas: 1) Maintaining water quality in the face of changing water use.Wastewater management is challenged by short-term water conservation during droughts and longer-term reductions in water use from indoor efficiency measures—conditions which are largelybeyond the sector’s control. Reductions in indoor water use can damage infrastructure and reduce the effectiveness of existing treatment processes. Such challenges may grow as severe droughts become more frequent with climate change and as water efficiency increases. Better coordination and information sharing with water suppliers, and sector-wide planning for future droughts, are key to addressing these changes. 2) Making smart recycled water investments. Wastewater agencies produce highly treated water that is increasingly being reused as a water supply. Coordination among wastewater and water supply agencies is essential to respond to the increasing demand for recycled water. Formalized planning for recycled water projects at the regional level will likely lead to more efficient processes and better outcomes. New investments must be responsive to changing water use, climate change, and pending regulations. 3) Balancing conflicting objectives within watersheds. Most wastewater treatment plants discharge treated water into inland watersheds. Adapting to declining water use and meeting increased demand for recycled water may conflict with environmental objectives and the demands of downstream users. Rivers and streams are expected to experience lower flows and higher temperatures, which will heighten threats to aquatic ecosystems. Resources to identify areas most at risk of conflict over the use of treated wastewater are needed, as are tools to evaluate the impacts of water recycling projects on the environment and downstream water users. The state should also analyze its policies to identify tradeoffs and resolve conflicts between its water supply, water quality, and environmental goals. Advancements in engineering and technology can help wastewater agencies adapt to a changing climate―but shifts in policy and planning will facilitate a more efficient and effective path toward building resilience. The latest drought provided a window into the looming challenges facing the wastewater sector. Forging new partnerships and evaluating the full range of climate-related risks will help the sector determine the best adaptations and policy improvements needed to prepare the wastewater sector for a more volatile future.

Managing Water for the Environment During Drought: Lessons from Victoria, Australia

Public Policy Institute of California (PPIC) | June 16th, 2016

Over the past 30 years the Australian state of Victoria developed innovative approaches to planning and setting priorities for environmental water, along with new tools t

Over the past 30 years the Australian state of Victoria developed innovative approaches to planning and setting priorities for environmental water, along with new tools to manage it. These sweeping reforms were in part a response to the Millennium Drought, a decade-long record dry spell that severely affected all water use in Victoria. California—currently in its fifth year of drought—has many similarities with Victoria, including significant challenges in managing the health of rivers and wetlands during times of extreme water scarcity. In this report, we examine the reforms enacted by Victoria and compare them to current environmental water management policies in California. This comparison highlights some key lessons learned by Victoria that may help guide how California adapts environmental water management to address future droughts. The environmental policy reforms enacted by Victoria were difficult and at times highly controversial. While it will take years to fully understand whether these reforms had their intended effect, there is no doubt that the state’s new approach to managing environmental water avoided some serious biological losses during the drought. Additionally, it is clear that the state is much better prepared for the next drought.

Marine heatwaves need clear definitions so coastal communities can adapt

Nature Portfolio (Springer Nature) | April 3rd, 2023

Marsh Sediment in Translation: A Review of Sediment Transport Across a Natural Tidal Salt Marsh in Northern San Francisco Bay

University of California, Davis (UC Davis) | March 15th, 2025

Deposition of inorganic sediment is essential for the sustainability of tidal salt marshes. Understanding variability in sediment sources and the processes of sediment de

Deposition of inorganic sediment is essential for the sustainability of tidal salt marshes. Understanding variability in sediment sources and the processes of sediment delivery to salt marshes are high priorities for decision-makers responsible for managing sediment and conserving and restoring marshes.

Martis Valley Groundwater Basin Sustainable Groundwater Management Act Alternative Submittal

Truckee Donner Public Utility District (TDPUD) | December 22nd, 2016

McMullin Area Groundwater Sustainability Agency Groundwater Sustainability Plan

McMullin Area Groundwater Sustainability Agency (MAGSA) | November 6th, 2019

McMullin Area Groundwater Sustainability Agency Groundwater Sustainability Plan (Revised)

McMullin Area Groundwater Sustainability Agency (MAGSA) | July 6th, 2022

Mean and Extreme Climate Change Impacts on the State Water Project

California Department of Water Resources (DWR) | August 27th, 2018

Warming temperatures, shifting hydrology, and rising sea levels will challenge management of California’s water resources. This study quantifies climate change risks t

Warming temperatures, shifting hydrology, and rising sea levels will challenge management of California’s water resources. This study quantifies climate change risks to California’s State Water Project (SWP) and federal Central Valley Project (CVP). This study uses the California Department of Water Resources’ (DWR’s) newly developed water planning model, CalSim 3.0, as a risk assessment tool. Impacts were assessed for 20 climate change scenarios (10 global climate models and two emission scenarios, representative concentration pathway (RCP) 4.5 and RCP 8.5). Water supply and water quality metrics evaluated include Delta exports, North of Delta Carryover storage, reservoir dead storage (i.e. when reservoir levels fall below the lowest outlets), and Delta salinity. Results for the driest future scenario were also analyzed to examine future drought impacts. In addition, a series of sensitivity tests were implemented to assess individual impacts of four climate change factors: flow seasonal pattern shift, sea level rise, annual flow volume change, and water demand change on the State Water Project and Central Valley Project operations. It was found that flow seasonal pattern shift will become a major climate change factor and sea level rise a secondary factor, leading to a half million‐acre feet of Delta export reduction as well as a roughly 25% decrease of North‐of‐Delta carryover storage by around 2060. The results also indicate that the extra runoff from early snow melting and higher percentage of rain in the winter and early spring is not conserved in reservoirs and thus cannot be used to meet the higher summer demand in the current SWP/CVP system. This extra water is released as flood water in the winter and early spring to become Delta outflow.

Measuring and Interpreting Multilayer Aquifer-System Compactions for a Sustainable Groundwater-System Development

American Geophysical Union (AGU) | March 23rd, 2021

Ever decreasing water resources and climate change have driven the increasing use of groundwater causing land subsidence in many countries. Geodetic sensors such as InSAR

Ever decreasing water resources and climate change have driven the increasing use of groundwater causing land subsidence in many countries. Geodetic sensors such as InSAR, GPS and leveling can detect surface deformation but cannot measure subsurface deformation. A single‐well, single‐depth extensometer can be used to measure subsurface deformation, but it cannot delineate the depths of major compaction and provide insight about the deformation mechanism throughout a complex aquifer system, unless man extensometers at different depths are used. We present a multilayer compaction well (MLCW), installed in a borehole, that uses magnetic rings to detect stratum compaction at 25 depths as deep as 300 m below land surface. Our laboratory and field assessments indicate 1 mm precision and accuracy for one single‐depth magnetic reading. We tested the performance of MLCW by measuring aquifer‐system compaction over the proximal, middle, and distal fans of the Choushui River Alluvial Fan (CRAF) that has long experienced severe land subsidence. The MLCW measurements were used to create time‐depth diagrams of compaction, showing different compaction rates at different layers of aquifers and aquitards to identify the depths of major compactions. The elastic (reversible) and inelastic (irreversible) compactions from MLCW were used in stress‐strain analyses to estimate skeletal specific storages and the safe groundwater levels, below which groundwater extractions have caused irreversible compactions. The hydrogeological parameters derived from MLCW measurements can help governmental agencies to determine effective land‐use and water‐use policies, and ascertain the best strategy for utilizing artificial recharge to prevent land subsidence and achieve sustainable groundwater management.

Measuring Progress Toward Universal Access to Water and Sanitation in California: Defining Goals, Indicators, and Performance Measures

Pacific Institute | September 15th, 2018

In January 2018, over half a million Californians were served by water utilities that were out of compliance with the Safe Drinking Water Act (SDWA). The worst outbreak o

In January 2018, over half a million Californians were served by water utilities that were out of compliance with the Safe Drinking Water Act (SDWA). The worst outbreak of Hepatitis A in recent memory occurred in 2016-2018 due to open defecation and lack of handwashing facilities for persons experiencing homelessness. California’s tribes continue to face problems of poor housing and water and sanitation service, with two-thirds of tribal communities reporting inadequate home plumbing in 2015.1 And the cost of water has increased for many, particularly among small and medium size systems, with 39 community water systems in the state charging more than $100 a month for 12 CCF of water. In response to the problem, California enacted the Human Right to Water in 2012, declaring that “Every human being has the right to safe, clean, affordable, and accessible water adequate for human consumption, cooking, and sanitary purposes.”