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 conservation benefits of urban heat mitigation

Nature Portfolio (Springer Nature) | October 20th, 2017

Many cities globally are seeking strategies to counter the consequences of both a hotter and drier climate. While urban heat mitigation strategies have been sho

Many cities globally are seeking strategies to counter the consequences of both a hotter and drier climate. While urban heat mitigation strategies have been shown to have beneficial effects on health, energy consumption, and greenhouse gas emissions, their implications for water conservation have not been widely examined. Here we use a suite of satellite- supported regional climate simulations in California to show that broad implementation of cool roofs, a heat mitigation strategy, not only results in significant cooling, but can also meaningfully decrease outdoor water consumption by reducing evaporative and irrigation water demands. Irrigation water consumption across the major metropolitan areas is reduced by up to 9% and irrigation water savings per capita range from 1.8 to 15.4 gallons per day across 18 counties examined. Total water savings are found to be the highest in Los Angeles county, reaching about 83 million gallons per day. Cool roofs are a valuable solution for addressing the adaptation and mitigation challenges faced by multiple sectors in California.

Water Conveyance Systems in California: Historic Context Development and Evaluation Procedures

State of California | December 1st, 2000

This study began as an attempt to develop a statewide thematic approach to surveying the ditches and canals which are a commonly encountered, but previously little studie

This study began as an attempt to develop a statewide thematic approach to surveying the ditches and canals which are a commonly encountered, but previously little studied, property type in California. In the past, canals were not always recognized as a type of cultural resource that might need study, and furthermore, although highways and other transportation facilities often intersect artificial waterways, projects that merely cross linear resources typically have little potential to affect them. As a result, structures such as canals, railroads, or roads that were bridged by a transportation project were rarely included in cultural resource studies. Now there is increased awareness that canals and other water conveyance facilities can be historically significant, and that when projects do have the potential to affect them, they need to be studied systematically.  However, important water conveyance systems are frequently extensive and sometimes quite complex, while transportation project effects on them are typically limited to a small segment of the entire property. Under these circumstances, developing a basic historical context would allow researchers to work from a baseline of existing knowledge, thus helping to achieve a suitable balance between the need for adequate information and expenditure of a reasonable level of effort. Because of California’s unique combination of natural resources, climate, topography, history, and development patterns, the state has a variety and number of water conveyance systems possessed by few if any other states.  Consequently, little guidance has been developed at a national or regional level, leaving California to develop its own statewide historic context and methodology. Sufficient research has now been conducted on California’s water conveyance systems to provide this historic context and survey methodology for the appropriate consideration of water conveyance systems, especially the frequently encountered canals and ditches, in order to take into account the effect of transportation projects on historic water conveyance facilities.

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 Dependent Recreation (Resource Management Strategy)

California Department of Water Resources (DWR) | July 29th, 2016

California residents and visitors can choose from a variety of water-dependent recreation activities managed by federal, State, and local agencies, as well as businesses

California residents and visitors can choose from a variety of water-dependent recreation activities managed by federal, State, and local agencies, as well as businesses and not-for-profit organizations. They may enjoy recreation activities in or on water, including fishing, swimming, skiing, and snowboarding, waterfowl hunting, motor boating, surfing, and kayaking. They also may participate in recreation activities that can be enhanced by water, such as wildlife viewing (including birding), picnicking, biking, relaxing on the beach, camping, and hiking. Although the latter activities do not require water, they are frequently enjoyed near waterways, lakes, floodways, and the sea. This resource management strategy report will not address water parks, swimming pools, and water- thirsty lawn-dependent recreational facilities, such as ball fields and golf courses; however, these are examples of popular off-stream recreational facilities that may require significant water resources.

Water Distribution System Efficiency: An Essential or Neglected Part of the Water Conservation Strategy for Los Angeles County Water Retailers?

University of California, Los Angeles (UCLA) | November 2nd, 2015

The water governance system in Los Angeles County is complex and fragmented. Potable water supply in metropolitan Los Angeles County relies on over 100 water retailers, b

The water governance system in Los Angeles County is complex and fragmented. Potable water supply in metropolitan Los Angeles County relies on over 100 water retailers, both public and private. It is unclear how the current system with many small water retailers will succeed in promoting integrated water resource management. Among other changes, there will need to be a shifting of water supply sources from predominantly imported to more local resources through conservation, recycled water usage, stormwater capture and groundwater management. The institutional capacity of water retailers to instigate this transition will depend heavily on their capacity to maintain reliable water deliveries without significant losses from leakage and failing infrastructure. Additionally, with drought conditions prevalent in eleven of the last fourteen years in California, and increasing evidence of climate change impacts on all water resources in California, it is crucial that water retailers minimize water losses through their distribution systems to match the increasingly stringent conservation efforts required of their customers, and to efficiently utilize scarce supplies.  Until this year, existing regulations for water agencies in California only requested information about system losses for potable water systems with more than 3000 connections. These numbers were reported through Urban Water Management Plans every five years. However, loss estimates through breaks and leaks have not been separated out from other non-revenue uses of water. To date, the most effective efforts to monitor water losses in California are voluntary and limited to members of the California Urban Water Conservation Council. To understand water distribution efficiency in urban Los Angeles County, we developed a questionnaire regarding leakage monitoring, system-wide water losses, and the implementation of pre-emptive best management practices. We surveyed 10 of the approximate total of 100 water retailers. The sample was representative of retailers of many types, sizes, and geographical locations in metropolitan Los Angeles and divided into tiers of size (small, mid-sized and large) based on the number of connections served. The survey questionnaire also addressed other metrics including per capita water consumption, leakage volumes, water loss estimation methodology, water loss estimates and infrastructure monitoring and replacement. The survey indicated several findings. First, the percentage of water loss due to breaks and leaks, though possibly misrepresentative, is still a widely used metric to measure water losses. Sixty percent of the agencies sampled still monitor only ‘unaccounted for water’ and not ‘real losses’. Retailers that do measure real losses reported them to be between 3-4% of total water supplied, which is an improbably low compared to international estimates as elaborated in the literature review section. Different water retailers were divided on the efficacy of leak detection technologies, which demands more education on available leak detection technology and their usage.  Larger retailers reported greater use of most of the best management practices addressed by our survey to maintain storage and distribution systems. Most small retailers did not report prioritizing adoption and implementation of best management practices to minimize water loss. Also, small Mutual Water Companies that we contacted did not have information on distribution water losses available publicly. To improve water efficiency, small retailers could pool resources and expertise to better detect, monitor and reduce distribution water losses. Investor-owned utilities and special water districts serve a large customer base, but as a group, they were least responsive of all the sample water retailers we contacted. In summary, California water regulations should aim at recommending crucial best management practices, ensuring accurate and verifiable water loss monitoring and prescribing an effective water loss metric and maximum acceptable standard as a roadmap for water retailers 

Water Facilities Including a Peripheral Canal [Proposition 9]

Department of Justice (DOJ) | June 9th, 1982

Water Facilities Including a Peripheral Canal Referendum Statute

State of California | June 1st, 1982

WATER FACILITIES INCLUDING A PERIPHERAL CANAL. REFERENDUM STATUTE. A "yes" vote approves, a "no" vote rejects, a law that will : Designate additional facilities and pr

WATER FACILITIES INCLUDING A PERIPHERAL CANAL. REFERENDUM STATUTE. A "yes" vote approves, a "no" vote rejects, a law that will : Designate additional facilities and programs, including a peripheral canal as units of Central Valley Project. Specify requirements regarding feasibility, environmental impacts, design construction, operation, financing, and protection and enhancement of fish and wildlife for project units. Require Water Resources Department to contract with named Delta agencies regarding users' rights, water quality, and benefit payments; and to immediately proceed with specified prerequisites to construction of peripheral canal . Required compliance with designated water quality standards and conditions . Specify other responsibilities and matters. Summary of Legislative Analyst's estimate of net state and local government fiscal impact: As Project has been planned and operated to be self-supporting, implementation under present policies would not require increase in state taxes or reduce funds for other state programs . Potential construction costs at 1981 prices are in excess of $3 .1 billion plus unknown additional costs, plus interest, to be financed by increased user charges.

Water Features of the Smith River Plain, Del Norte County, California

U.S. Geological Survey (USGS) | December 1st, 1957