Accounting for California’s Water

Public Policy Institute of California (PPIC) | July 13th, 2016

Understanding California’s water balance sheet—how much there is, who has claims to it, and what is actually being “spent”—is key to effectively managing the st

Understanding California’s water balance sheet—how much there is, who has claims to it, and what is actually being “spent”—is key to effectively managing the state’s limited water supply in support of a healthy economy and environment. The latest drought has spotlighted serious gaps and fragmentation in California’s water accounting system. In this report, we identify gaps in California’s water information systems. We recommend that the state adopt an overarching goal of modernizing its water accounting, and that key state agencies—supported by an oversight committee of key stakeholders and independent experts—develop and adopt a common accounting framework. We outline a dozen priority actions to strengthen water accounting by: improving measurements and estimates of water availability and use; firming up legal claims on water rights and water reserved for the environment; establishing protocols, standards, and models for transparent water accounting at all levels across the state; and making water information more available and accessible to water managers, water users, policymakers, and the public.

Accounting for Climate Change

California Department of Water Resources (DWR) | April 29th, 2010

In recent years, evidence that global climate will have significant effects on water resources in California has continued to accumulate. Climate change can affect the am

In recent years, evidence that global climate will have significant effects on water resources in California has continued to accumulate. Climate change can affect the amount, timing, and form of precipitation, whether rain or snow, that California receives, as well as the sea level of the Pacific Ocean. Moreover, changes in weather, especially temperature, and atmospheric composition can affect water use and consumption. Changes in climate have occurred during the 20th century, with noticeable warming in the last two decades. Most scientists feel that changes during the last several decades are likely mostly due to human activities, but natural causes and variability cannot be ruled out as a significant component. Likewise, projections of amount of warming and other climate changes during the 21st century are wide ranging, depending on assumptions and models. A major cause of expected climate change is the increasing amounts of greenhouse gases, such as carbon dioxide, in the atmosphere as a result of man’s activities. These gases, as well as water vapor, allow solar radiation to pass inward through the atmosphere, but trap the longer wave infrared radiation reflected back from the earth’s surface. Greenhouse gases are accumulating in the atmosphere; the following chart shows the gradual build up in carbon dioxide at Mauna Loa in Hawaii, as measured by Scripps Institution of Oceanography scientists. The annual cycle is caused by northern hemisphere vegetation uptake during the growing season. Other significant greenhouse gases are methane, nitrous oxide, halocarbons (like freon and its replacements), and, of course, water vapor itself. Cloud cover is an important element in the global radiation balance. Whatever the causes, the prospects of significant changes warrant examination of how the State’s water infrastructure and natural systems can accommodate or adapt to climate changes and whether more needs to be done to detect, evaluate and respond to water resource system effects. Many uncertainties remain, primarily on the degree of change to be expected. Responsible planning requires that the California water planning community work with climate scientists and others to reduce these uncertainties and to begin to prepare for those impacts that are well understood, already appearing as trends, or likely to appear. In this section we review possible impacts and address some of the responses appropriate for water planners and managers.

Accounting for Water "Wasted to the Sea"

University of California, Davis (UC Davis) | April 19th, 2018

Freshwater outflow from the Sacramento–San Joaquin Delta is a contentious management issue. Once mixed with salt water of San Francisco Bay, outflow is often characteri

Freshwater outflow from the Sacramento–San Joaquin Delta is a contentious management issue. Once mixed with salt water of San Francisco Bay, outflow is often characterized as having no value for urban and agricultural water supply, and thus “wasted to the sea.” In the July issue of San Francisco Estuary and Watershed Science, Cloern et al. (2017) showed how outflow from the Delta provides multiple and diverse benefits to the San Francisco estuary. Rather than being “wasted,” this outflow improves ecosystem conditions and water quality, and reduces wastewater treatment costs. The Cloern et al. (2017) essay highlights the importance of considering the multiple benefits of water as it moves within and out of the Delta. To do this, however, California needs a better water accounting system. In this report, we present an alternative approach. For the period 1980–2016, we assign inflow to the Delta to four categories: 1. Water used for diversions, 2. Outflow needed to meet salinity standards for diversions, 3. Outflow to meet ecosystem regulations, and 4. Water that results in outflow because of a lack of capacity for diversion. This approach highlights that much of the outflow from the Delta — particularly during dry periods — achieves multiple economic and environmental benefits and is hardly “wasted to the sea.”

Achievements in Conservation, Recycling, and Groundwater Recharge Covering Fiscal Year July 2018-June 2019

Metropolitan Water District of Southern California (MWD) | March 1st, 2020

Achieving Equitable, Climate-Resilient Water and Sanitation for Frontline Communities Water, Sanitation, and Climate Change in the United States Series, Part 3

Pacific Institute | March 18th, 2025

This report contains numerous documented efforts of ways that frontline communities are making progress toward equitable, climate-resilient water and sanitation. Built in

This report contains numerous documented efforts of ways that frontline communities are making progress toward equitable, climate-resilient water and sanitation. Built infrastructure is being adapted to better withstand the impacts of extreme storms, floods, and drought. Technologies and innovations are being designed and deployed in remote, hard-to-reach communities to deliver climate-resilient water and sanitation to homes for the first time. Natural infrastructure strategies are being used to enhance the climate resilience of water and sanitation by helping recharge aquifers and attenuate floodwaters, for example. Water managers and planners are incorporating climate resilience and centering frontline communities in efforts to deliver equitable, climate-resilient water and sanitation access to all. Frontline communities are overcoming barriers to accessing the financial resources that they need to pay for climate adaptation of water and sanitation or recover and respond to climate disasters. Climate and water knowledge and information from government agencies, water managers, local experts, and climate scientists are being integrated with place-based knowledges to ensure frontline communities and people in positions of power and authority can understand and access the data and information they need for decision making. The capacity of water and sanitation systems staff and decision makers is growing to better center the needs of frontline communities, educate and support the water and sanitation sector workforces in improving climate resilience, and build connections with interdependent sector. This is part three  in the Pacific Institute’s three-part Water, Sanitation, and Climate Change in the United States series. Click here for part one and  here for part two.

Achieving Groundwater Access for All: Why Groundwater Sustainability Plans are Failing Many Users

Groundwater Leadership Forum | July 3rd, 2023

California made a serious commitment to bring the most depleted groundwater basins back into balance when it passed the Sustainable Groundwater Management Act (SGMA) in 2

California made a serious commitment to bring the most depleted groundwater basins back into balance when it passed the Sustainable Groundwater Management Act (SGMA) in 2014. This commitment is being carried out at the local level through the formation of hundreds of new groundwater agencies, the launch of basin-level planning processes, and the creation of groundwater sustainability plans. This report summarizes the results of a scientific study published in Nature Communications. that analyzed the degree to which these groundwater plans equitably integrate and protect vulnerable groundwater users, and suggests course corrections in the ongoing SGMA process to ensure we are preparing our groundwater basins for a changed climate.

Achieving Realistic Runoff in the Western United States with a Land Surface Model Forced by Dynamically Downscaled Meteorology

American Meteorological Society (AMS) | February 14th, 2023

This study provides useful guidance for improving a land surface model to accurately represent runoff across a spatially extensive and hydroclimatically diverse region (t

This study provides useful guidance for improving a land surface model to accurately represent runoff across a spatially extensive and hydroclimatically diverse region (the western United States). The land surface model is updated to represent runoff more accurately at gauged basins, and then additionally updated for basins without observational data using a mathematical approach called the donor-basin method. We make use of a regional climate model’s reanalysis-derived meteorological data and its underlying land surface model to achieve realistic runoff. The calibrated land surface model can thus be tightly coupled in subsequent studies in a manner that should more accurately reflect runoff conditions. Findings from this study will serve as a useful reference for the atmospheric (and hydrologic) modeling communities and their ability to represent large-scale hydrology accurately.

Achieving State Goals for the Sacramento-San Joaquin Delta

Legislative Analyst's Office (LAO) | January 15th, 2015

The Sacramento-San Joaquin Delta (Delta) is a biodiverse ecosystem that covers about 1,150 square miles and supports over 700 species of fish and wildlife. The Delta is a

The Sacramento-San Joaquin Delta (Delta) is a biodiverse ecosystem that covers about 1,150 square miles and supports over 700 species of fish and wildlife. The Delta is an important source of water for the state and is used to convey water from Northern California to Southern California. The Delta faces several significant problems, including: (1) a decline in key native fish species, (2) reductions in the amount of Delta water available for use elsewhere, (3) water pollutants that cause harm to species and increase treatment costs, and (4) levees at significant risk of failure. The state has engaged in numerous efforts to address these problems and achieve its "coequal goals" for the Delta: water supply reliability and ecosystem restoration. There are many opportunities for the Legislature to improve the success of these efforts. We identified several issues for its consideration, including (1) demands for Delta water, (2) uncertain funding sources and slow implementation of some key activities, (3) limits on the effectiveness of governance in the Delta, and (4) challenges to restoring the Delta ecosystem. By addressing some of these issues, the Legislature can improve the likelihood that its goals and objectives for the Delta will be realized.

Achieving the Human Right to Water in California: An Assessment of the State's Community Water Systems

Office of Environmental Health Hazard Assessment (OEHHA) | January 15th, 2021

The Human Right to Water Framework and Data Tool (CalHRTW 1.0) provides a consolidated, stand-alone, quantitative assessment of baseline conditions in the quality, acces

The Human Right to Water Framework and Data Tool (CalHRTW 1.0) provides a consolidated, stand-alone, quantitative assessment of baseline conditions in the quality, accessibility and affordability of California’s drinking water. This assessment can help screen for drinking water challenges and analyze changes over time and complements existing cumulative impacts analyses (e.g., CalEnviroScreen (OEHHA, 2021b)) by providing information at a greater level of detail regarding drinking water.

Adaptability and adaptations of California’s water supply system to dry climate warming

Climatic Change (Springer) | November 27th, 2007

Economically optimal operational changes and adaptations for California’s water supply system are examined for a dry form of climate warming (GFDL CM2.1 A2) with year 2

Economically optimal operational changes and adaptations for California’s water supply system are examined for a dry form of climate warming (GFDL CM2.1 A2) with year 2050 water demands and land use. Economically adaptive water management for this climate scenario is compared to a similar scenario with the historical climate. The effects of population growth and land use alone are developed for comparison. Compared with the historic hydrology, optimized operations for the dry climate warming scenario raise water scarcity and total operation costs by $490 million/year with year 2050 demands. Actual costs might be somewhat higher where non-economic objectives prevail in water management. The paper examines the economical mix of adaptation, technologies, policies, and operational changes available to keep water supply impacts to such modest levels. Results from this screening model suggest promising alternatives and likely responses and impacts. Optimized operations of ground and surface water storage change significantly with climate. Dry-warm climate change increases the seasonal storage range of surface reservoirs and aquifers. Surface reservoir peak storage usually occurs about a month earlier under dry-warm climate change.