Water and Energy Sector Vulnerability to Climate Warming in the Sierra Nevada: Water Year Classification in Non?Stationary Climates

California Energy Commission (CEC) | July 31st, 2012

This paper explores the sensitivity of water indexing methods to climate change scenarios to better understand how water management decisions and allocations will be affe

This paper explores the sensitivity of water indexing methods to climate change scenarios to better understand how water management decisions and allocations will be affected by climate change. Many water management decisions, such as environmental flow requirements and water supply allocations, are based on numerical “water year type” designations. Water year type designations vary by region and index, but most are defined by some measure of runoff in the current water year compared to average historical runoff, with numerical thresholds categorizing year types. Climate change is anticipated to alter the timing and volume of runoff, and change the relative frequency of water year types as presently defined. California’s Sacramento Valley and San Joaquin Valley Indices are used as a case study to examine climatic changes. These indices provide a framework for allocating and transferring water among users. Streamflow estimates for 1951–2099 from the climate-forced Variable Infiltration Capacity hydrologic model are used to estimate potential changes in runoff and water year type frequency, using six global circulation models for the A2 and B1 emissions scenarios. Results vary by emissions scenario and global circulation model, but indicate that critically dry water years in the Sacramento Valley and San Joaquin Valley are expected to be about 8 percent and 32 percent more likely by the latter half of the twenty-first century, respectively, if water year type definitions remain unchanged. If current water year type thresholds are maintained, more years will be classified as dry and less water will be allocated for environmental outflows, perhaps failing to provide adequate hydrologic variability to support species, habitats, and ecosystems. If thresholds are redefined to reflect the historical distribution of year types, the burden of climate change falls to consumptive users and water exporters. This case study illustrates how water policy and allocation frameworks were designed assuming climatic stationarity, and that adapting water policy (or maintaining the status quo) affects which users bear the burden of climate change.

Water and the California economy

Public Policy Institute of California (PPIC) | May 17th, 2012

California’s economy can grow and prosper despite droughts and water shortages caused by a changing climate—but only if threats to the water system are addressed now.

California’s economy can grow and prosper despite droughts and water shortages caused by a changing climate—but only if threats to the water system are addressed now. So far, innovative water management has supported the needs of a growing population but serious concerns remain, including water supply reliability and declining groundwater basins.

Water and the COVID-19 Pandemic Impacts on Municipal Water Demand

Pacific Institute | July 2nd, 2020

Water and the Future of the San Joaquin Valley

Public Policy Institute of California (PPIC) | February 14th, 2019

The San Joaquin Valley—California’s largest agricultural region and an important contributor to the nation’s food supply—is in a time of great change. The valle

The San Joaquin Valley—California’s largest agricultural region and an important contributor to the nation’s food supply—is in a time of great change. The valley is ground zero for many of California’s most difficult water management problems—including groundwater overdraft, drinking water contamination, and declines in habitat and native species. Local water supplies are limited, particularly in the southern half of the region. To irrigate their crops, many farmers use water imported from the Sacramento–San Joaquin Delta. But in many places farmers have also relied on groundwater overdraft—pumping groundwater in excess of the rate at which it is replenished. Worsening droughts, increasing regulations to protect endangered native fishes, and growing demand by Southern California for Delta imports have compounded surface water scarcity. The state’s Sustainable Groundwater Management Act (SGMA) requires local water users to bring groundwater use to sustainable levels by the early 2040s. This will have a broad impact on valley agriculture and the regional economy in coming years—likely including some permanent idling of farmland. This report explores three key challenges facing the San Joaquin Valley and reviews the most promising approaches to address them:  Balancing water supplies and demands. To close the groundwater deficit, groundwater sustainability agencies in the valley’s overdrafted basins will have to augment supplies, reduce demands, or use some combination of these two approaches. A range of options are under consideration but they are not equally effective or practical.  Addressing groundwater quality challenges. Poor groundwater quality impairs drinking water supplies in disadvantaged rural communities, reduces long-term agricultural prosperity, and degrades ecosystems. Providing safe drinking water is an urgent priority. Over the longer term, parties will also need to manage water quantity and quality together, to take advantage of synergies and avoid unintended consequences. The necessary coordination will be challenging because the various programs addressing valley water quality issues are carried out by numerous local and regional entities, whose lines of responsibility and geographic boundaries do not neatly align.  Fostering beneficial water and land use transitions. Effectively addressing water scarcity and the resulting land use changes in the San Joaquin Valley offers opportunities to put lands coming out of production to good use—and gain “more pop per drop” from limited water resources. Multiple-benefit approaches to water and land management can enhance groundwater recharge and improve air and water quality. They can also promote healthier soils, new recreational opportunities, additional flood protection, improved habitat, and new revenue streams for private landowners engaging in conservation-oriented management. Addressing these complex and intertwined issues requires significant changes in water and land management and a major ramp-up in cooperation and coordination among a wide circle of stakeholders. Pursuing solutions that deliver multiple benefits will boost the chances of success overall. The entire region—and California as a whole—will benefit if solutions to these challenges are cost-effective and support the valley’s economy while improving public health and the natural environment.

Water Budgets: Foundations for Effective Water-Resources and Environmental Management

U.S. Geological Survey (USGS) | August 30th, 2007

Water budgets provide a means for evaluating availability and sustainability of a water supply. A water budget simply states that the rate of change in water stored in an

Water budgets provide a means for evaluating availability and sustainability of a water supply. A water budget simply states that the rate of change in water stored in an area, such as a watershed, is balanced by the rate at which water flows into and out of the area. An understanding of water budgets and underlying hydrologic processes provides a foundation for effective water-resource and environmental planning and management. Observed changes in water budgets of an area over time can be used to assess the effects of climate variability and human activities on water resources. Comparison of water budgets from different areas allows the effects of factors such as geology, soils, vegetation, and land use on the hydrologic cycle to be quantified. Human activities affect the natural hydrologic cycle in many ways. Modifications of the land to accommodate agriculture, such as installation of drainage and irrigation systems, alter infiltration, runoff, evaporation, and plant transpiration rates. Buildings, roads, and parking lots in urban areas tend to increase runoff and decrease infiltration. Dams reduce flooding in many areas. Water budgets provide a basis for assessing how a natural or human-induced change in one part of the hydrologic cycle may affect other aspects of the cycle. This report provides an overview and qualitative description of water budgets as foundations for effective water-resources and environmental management of freshwater hydrologic systems. Perhaps of most interest to the hydrologic community, the concepts presented are also relevant to the fields of agriculture, atmospheric studies, meteorology, climatology, ecology, limnology, mining, water supply, flood control, reservoir management, wetland studies, pollution control, and other areas of science, society, and industry. The first part of the report describes water storage and movement in the atmosphere, on land surface, and in the subsurface, as well as water exchange among these compartments. Our ability to measure these phenomena and inherent uncertainties in measurement techniques also are discussed. The latter part of the report presents a number of case studies that illustrate how water-budget studies are conducted, documents how human activities affect water budgets, and describes how water budgets are used to address water and environmental issues.

Water Column Selenium Concentrations in the San Francisco Bay-Delta: Recent Data and Recommendations for Future Monitoring

San Francisco Estuary Institute (SFEI) | August 1st, 2017

The San Francisco Bay Regional Water Board developed a Total Maximum Daily Load (TMDL) and implementation plan for selenium in North San Francisco Bay (NSFB) in 2015.1 T

The San Francisco Bay Regional Water Board developed a Total Maximum Daily Load (TMDL) and implementation plan for selenium in North San Francisco Bay (NSFB) in 2015.1 The TMDL is based on attainment of water column and fish tissue target concentrations protective of human health, aquatic life, and wildlife, and was approved by the US Environmental Protection Agency in August, 2016. Analyses in support of the TMDL synthesized the results of different monitoring efforts to characterize selenium concentrations in water and biota in the Estuary. For water quality evaluation in the TMDL, the sources of observational data included studies of selenium speciation across the estuarine salinity gradient, performed in 1999-2000 and again in 2010 and 2012 (Cutter and Cutter 2004, Doblin et al. 2006, Tetra Tech, 2012), as well as samples collected by the San Francisco Bay Regional Monitoring Program (RMP). Changes in wastewater treatment from the five major refineries in NSFB were implemented in the late 1990s, leading to significant reductions in selenium loads. Data at Estuary center-line locations showed small changes for dissolved selenium in the mid-salinity range and no trends in particulate selenium (Baginska, 2015). As part of the TMDL, water quality modeling analyses were performed to characterize NSFB selenium concentrations under a range of hydrologic conditions and changing point-source loads (Baginska, 2015). Water column selenium concentration data in the NSFB and Delta continue to be collected at selected locations, although these data have not been systematically evaluated following the analyses presented in the TMDL reports. In the near term, possible changes that may cause selenium concentrations to change in the NSFB and Delta include concentration changes in the inflow from the San Joaquin River basin, changes in refinery inputs, changes in stormwater and tributary loads from the Bay margin, and changes in overall Central Valley hydrological conditions, such as the extreme wet and dry periods that occurred between 2012 and 2017. Other drivers, such as nutrient concentrations and algal levels, may also play a role, especially on the concentrations of selenium on particulates.

Water Demand Projection Accuracy and Demand Management Trends in California Cities

American Geophysical Union (AGU) | November 21st, 2025

This study investigates the accuracy of long-term water demand projections and tracks the evolution of water demand management incentives across 61 California water suppl

This study investigates the accuracy of long-term water demand projections and tracks the evolution of water demand management incentives across 61 California water suppliers from 2000 to 2020. Through a systematic analysis of Urban Water Management Plans, we find that water suppliers consistently overestimated future demand by an average of 25% for 5-year projections and 74% for 20-year projections. This overestimation stems primarily from assumptions about per capita water demand rather than population growth estimates. While suppliers generally projected stable or increasing per capita demand, actual water demand per capita declined by 1.9% annually between 2000 and 2020, leading to a decoupling of water demand from population growth. Concurrently, we document a substantial increase in water demand management incentives, with non-voluntary regulations emerging as the dominant demand management approach by 2020, largely driven by state policies like the Model Water Efficient Landscape Ordinance and California Green Building Standards. Demand management efforts have evolved from primarily indoor and educational initiatives toward outdoor-focused non-voluntary regulations and rebates. This shift appears closely linked to the reduction in per capita demand that suppliers failed to fully capture in their water demand projections. Our findings underscore the importance of incorporating dynamic conservation trends into demand projections and suggest that suppliers should develop more sophisticated forecasting methods that account for the continuing evolution of water efficiency incentives. This research provides valuable insights for water resource planners seeking to improve the accuracy of water demand projections in an era of increasing conservation and climate uncertainty.

Water for a Growing Bay Area: How the region can grow without increasing water demand

Pacific Institute | October 21st, 2021

The San Francisco Bay Area is at a crossroads. The region, blessed with a beautiful natural setting, multiple shipping ports and world-class universities, is a driver of

The San Francisco Bay Area is at a crossroads. The region, blessed with a beautiful natural setting, multiple shipping ports and world-class universities, is a driver of global economic growth. But the region’s housing supply has not kept up with population growth. Many low-income households, disproportionately made up of people of color, have been forced into overcrowded and substandard housing or displaced from the urban center to new neighborhoods far from their jobs, friends and families. The most vulnerable have lost their homes entirely and are among the region’s 35,000 unhoused people. Over the next half-century, the Bay Area’s need to add housing will only grow more intense. The region is projected to add 2 million new jobs by 2070, which would attract as many as 6.8 million people, and needs to build at least 2.2 million new housing units just to prevent housing affordability from worsening. This represents 83% more people, 74% more housing units and 38% more jobs over the next 50 years.

Water for Growth: California’s New Frontier

Public Policy Institute of California (PPIC) | July 25th, 2005

California’s population is expected to add another 14 million people by 2030, reaching a total of 48 million. One of the most serious concerns of policymakers is wh

California’s population is expected to add another 14 million people by 2030, reaching a total of 48 million. One of the most serious concerns of policymakers is whether the state will be able to supply the water needed to sustain such a population. Although many large water projects in the past were undertaken with state and federal leadership, most current options are local or regional in scope. The frontline agencies responsible for water supply are the hundreds of municipal utilities serving the state’s residential and commercial customers. In this report, the author examines how well California is faring in meeting the water supply challenges of growth throughout the state and the extent to which local governments are integrating water supply concerns into their land-use planning. The report also evaluates progress in implementing the new “show me the water” laws, SB 610 and SB 221, which require up-front screening of water availability for large development projects.

Water Forward 2024 Plan Report - Austin's 100 Year Plan

City of Austin | December 6th, 2024

Water Forward 2024 is Austin’s 100-year integrated water resource plan. The purpose of Water Forward is to develop and implement diverse and environmentally conscious w

Water Forward 2024 is Austin’s 100-year integrated water resource plan. The purpose of Water Forward is to develop and implement diverse and environmentally conscious water management strategies to adapt to growth, drought, and climate change and ensure a sustainable, resilient, equitable, and affordable water future for our community for the next 100 years. Austin Water has developed this plan to address near- and long-term water needs through a collaborative process in alignment with guiding principles crafted to reflect the Austin community’s values.