Conjunctive Management and Groundwater Storage (Resource Management Strategy)

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

Conjunctive management or conjunctive use refers to the coordinated and planned use and management of both surface water and groundwater resources to maximize the availab

Conjunctive management or conjunctive use refers to the coordinated and planned use and management of both surface water and groundwater resources to maximize the availability and reliability of water supplies in a region to meet various management objectives. Surface water and groundwater resources typically differ significantly in their availability, quality, management needs, and development and use costs. Managing both resources together, rather than in isolation, allows water managers to use the advantages of both resources for maximum benefit. Conjunctive management thus involves the efficient use of both resources through the planned and managed operation of a groundwater basin and a surface water storage system combined through a coordinated conveyance infrastructure. Water is stored in the groundwater basin that is planned to be used later by intentionally recharging the basin when excess water supply is available, for example, during years of above-average surface water supply or through the use of recycled water. The necessity and benefit of conjunctive water management are apparent when surface water and groundwater are hydraulically connected. Well-planned conjunctive management that prevents groundwater depletion by maintaining baseflow to streams and support for ecosystem services not only increases the reliability and the overall amount of water supply in a region, but also provides other benefits such as flood management, environmental water use, and water quality improvement.  

Considerations for Management of the Mouth State of California’s Bar-built Estuaries

Southern California Wetlands Recovery Project | January 10th, 2019

Bar-built estuaries are the dominant estuary type in California, and many of these small estuaries are subject to closure with a sand barrier separating a lagoon

Bar-built estuaries are the dominant estuary type in California, and many of these small estuaries are subject to closure with a sand barrier separating a lagoon estuary from the ocean for days, months or even years. In the lagoon impounded behind the sand barrier, water levels may rise or fall depending on net water budget and water quality extremes may develop. These conditions and the obstruction of fish passage motivate managed breaching of the sand barrier in many systems statewide – an intervention that alleviates or preempts environmental problems, but which also can result in undesirable secondary impacts due to the acute effect of a single breach or the chronic effect of repeated breaching over years. Management decisions are based on an implicit trade-off between anticipated benefits and costs that depend on the values and priorities of stakeholders. This report was written to provide an overview of considerations for managed breaching in California. It presents a synthesis of processes and phenomena related to mouth closure and breaching in general and uses this to identify potential impacts of breaching, without intending any judgment of which impacts are more or less desirable. Three specific systems are reviewed in detail: Los Peñasquitos Lagoon in San Diego County, Scott Creek Estuary in San Mateo County and Russian River Estuary in Sonoma County. While there are fundamental similarities in the closure and breaching cycle across all bar-built estuaries statewide, there is also an immense diversity between these systems due to differences in size, in hydrology (wet north to dry south), and in development (rural, urban, agricultural, road/rail). The local community is likely to develop the best management strategy where there is significant effort and experience in local monitoring, science, and stakeholder consultation. However, where there is limited monitoring, science or consultation, the considerations outlined in this report provide preliminary guidance – and comparison with one of the study systems can provide more specific insight to the potential impacts of breaching management decisions. We synthesize current understanding related to how mouth state influences estuary functions and conditions, which in turn affect ecological services. While both natural and managed breaching affect many processes and phenomena in the estuary, breaching events and managed breaching regimes do not occur in isolation and many other factors affect the estuary functions and conditions, including freshwater inputs, the adjacent landscape, and stressors in the watershed. However, managed breaching is one of very few short-term management options and therefore a valuable adaptive management tool, specifically in systems that are already perturbed or impacted by human encroachment. Although emergency breaches may be required in rare occasions, our recommendation is to develop a breaching strategy for specific systems in which breaching has been used or in which it is likely to be used as a management tool. In this context, we recommend ways in which science can provide improved support for management decisions and identify a few systems in California in which there is already a well-developed, science-based management plan. Associated document: "Wetlands on the Edge: The Future of Southern California's Wetlands - Regional Strategy 2018"

Considerations for Selecting Climate Projections for Water Resources, Planning, and Environmental Analyses

U.S. Bureau of Reclamation (USBR) | March 2nd, 2016

For over a century, Reclamation’s mission has focused on managing water resources in the Western United States. Water resources, planning, and environmental studies car

For over a century, Reclamation’s mission has focused on managing water resources in the Western United States. Water resources, planning, and environmental studies carried out to support Reclamation’s mission have routinely considered hydrologic variability, including variability of water supplies and demands from season to season and year to year. Because weather and climate are two of the primary drivers of water supply and demand, Reclamation studies have also routinely considered weather and climate variability. The SECURE Water Act directs Reclamation to evaluate the risks and impacts of climate change in long-range planning and decision making (see Section 1.1. of the main report), including: •Water resources and environmental analyses •Planning studies •Design and analysis of current and proposed infrastructure and operating plans Considering climate change involves analyzing projected changes in weather and climate conditions as well as the effects of these changes on water supplies, demands, and management.  This document provides an overview of the primary considerations relevant to selecting climate projection information for use in a given water resources, planning, or environmental analysis. Audience For technical specialists involved in selecting and using climate projections for a given study—e.g., climatologist, hydrologists, and water resources engineers— this document provides a brief overview of the models and methods used to develop climate projections (Section 2.) and relevant considerations for selecting an appropriate climate projection dataset and set of climate projections to meet their specific study objectives (Section 3.). This document also provides a detailed summary of available climate projection datasets (Section 4.) and established methods for selecting climate projections for use in a detailed analysis (Section 5.). For other study team members involved in interpreting and documenting the use of climate change information in a given study—e.g., planners, environmental specialists, and resource managers—this document provides an overview of how climate projections are developed (Section 2.) and the choices and considerations involved in selecting climate projections for analysis in the study (Section 3.).

Contribution of historical precipitation change to US flood damages

Publisher not available | January 26th, 2021

Precipitation extremes have increased across many regions of the United States, with further increases anticipated in response to additional global warming. Quantifying

Precipitation extremes have increased across many regions of the United States, with further increases anticipated in response to additional global warming. Quantifying the impact of these precipitation changes on flood damages is necessary to estimate the costs of climate change. However, there is little empirical evidence linking changes in precipitation to the historically observed increase in flood losses. We use >6,600 reports of state-level flood damage to quantify the historical relationship between precipitation and flood damages in the United States. Our results show a significant, positive effect of both monthly and 5-d state-level precipitation on state-level flood damages. In addition, we find that historical precipitation changes have contributed approximately one-third of cumulative flood damages over 1988 to 2017 (primary estimate 36%; 95% CI 20 to 46%), with the cumulative impact of precipitation change totaling $73 billion (95% CI 39 to $91 billion). Further, climate models show that anthropogenic climate forcing has increased the probability of exceeding precipitation thresholds at the extremely wet quantiles that are responsible for most flood damages. Climate models project continued intensification of wet conditions over the next three decades, although a trajectory consistent with UN Paris Agreement goals significantly curbs that intensification. Taken together, our results quantify the contribution of precipitation trends to recent increases in flood damages, advance estimates of the costs associated with historical greenhouse gas emissions, and provide further evidence that lower levels of future warming are very likely to reduce financial losses relative to the current global warming trajectory.

Contribution of the Pacific Decadal Oscillation to global mean sea level trend

American Geophysical Union (AGU) | October 3rd, 2013

Understanding and explaining the trend in global mean sea level (GMSL) have important implications for future projections of sea level rise. While measurements from sa

Understanding and explaining the trend in global mean sea level (GMSL) have important implications for future projections of sea level rise. While measurements from satellite altimetry have provided accurate estimates of GMSL, the modern altimetry record has only now reached 20 years in length, making it difficult to assess the contribution of decadal to multi-decadal climate signals to the global trend. Here, we use a sea level reconstruction to study the 20 year trends in sea level since 1950. In particular, we show that the Pacific Decadal Oscillation (PDO) contributes significantly to the 20 year trends in GMSL. We estimate the PDO contri-bution to the GMSL trend over the past 20 years to beapproximately 0.49 ± 0.25 mm/year and find that removing the PDO contribution reduces the acceleration in GMSL estimated over the past 60 years. 

Conveyance - Delta (Resource Management Strategy)

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

The Sacramento-San Joaquin Delta (Delta) is the confluence point of the Sacramento and San Joaquin rivers as water is naturally conveyed westward from upstream water basi

The Sacramento-San Joaquin Delta (Delta) is the confluence point of the Sacramento and San Joaquin rivers as water is naturally conveyed westward from upstream water basins to the bays connected to the Pacific Ocean (Figure 1). In its natural state, the Delta was a vast marsh and floodplain dissected by meandering channels and sloughs. Even in today’s highly altered environment, the Delta remains a critical ecosystem and dynamic habitat that is home to hundreds of aquatic and terrestrial species, including many species endemic to the area and a number that are designated as threatened or endangered by the federal Endangered Species Act (ESA) and California Endangered Species Act (CESA). The Delta is also a centerpiece of California’s water system. The conveyance of water through the Delta supplies water for more than 25 million Californians. The water conveyed through the Delta also supports farms and ranches stretching from the north Delta to California-Mexico border, which collectively produce nearly half of the nation’s domestically grown fresh produce and supports a $27 billion agricultural industry. In addition to being a key agricultural region itself and recreational destination, the Delta supports extensive infrastructure of statewide importance, such as aqueducts, natural gas pipelines, electricity transmission lines, railroads, shipping channels, and highways.

Conveyance — Regional/Local (Resource Management Strategy)

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

Conveyance provides for the movement of water, geographically connecting the supply to the demand. Conveyance infrastructure includes natural watercourses as well as huma

Conveyance provides for the movement of water, geographically connecting the supply to the demand. Conveyance infrastructure includes natural watercourses as well as human-made facilities like canals, pipelines, and flood bypasses. Examples of natural watercourses include streams, rivers, floodplains, and groundwater aquifers. Conveyance facilities range in size from small, local, end-user distribution systems to the large systems that move water to and from distant areas. Conveyance facilities also require associated infrastructure such as pumping plants, diversion structures, fish ladders, and fish screens. Regional and local water supply conveyance is discussed in this resource management strategy report.

Costs of Ecosystem Management Actions for the Sacramento-San Joaquin Delta

Public Policy Institute of California (PPIC) | April 22nd, 2013

California is at a critical juncture on policy for the Sacramento–San Joaquin Delta. This report summarizes the results of a wide-ranging study of cost-effective wa

California is at a critical juncture on policy for the Sacramento–San Joaquin Delta. This report summarizes the results of a wide-ranging study of cost-effective ways to improve the health of the Delta ecosystem. It highlights the need for science-based, integrated management of the many sources of ecosystem stress. The report also recommends improvements to the highly fragmented system of oversight that now involves dozens of federal, state, and local agencies. Several companion reports contain related findings: Aquatic Ecosystem Stressors in the Sacramento–San Joaquin Delta (Mount et al. 2012) summarizes the science of Delta ecosystem stressors for a policymaking audience. Integrated Management of Delta Stressors: Institutional and Legal Options (Gray et al. 2013) lays out proposals for institutional reform of science, management, and regulation. Scientist and Stakeholder Views on the Delta Ecosystem (Hanak et al. 2013) presents detailed results of the two surveys conducted by the report’s authors. Stress Relief: Prescriptions for a Healthier Delta Ecosystem (Hanak et al. 2013) summarizes the overall research project and the recommendations it generated. Where the Wild Things Aren’t: Making the Delta a Better Place for Native Species (Moyle et al. 2012) outlines a realistic long-term vision for achieving a healthier ecosystem.

Counties Wresting Control: Local Responses to California's Statewide Water Market

University of Denver Water Law Review (UDWLR) | January 1st, 2003

Customer Debt and Lost Revenue: The Financial Impacts of COVID-19 on Small Community Water Systems

Pacific Institute | May 4th, 2021

This report provides information on revenue losses experienced by small community water systems (SCWS) in the United States and debt accumulated by their customers during

This report provides information on revenue losses experienced by small community water systems (SCWS) in the United States and debt accumulated by their customers during the COVID-19 pandemic. More than 45,000 SCWS, defined as systems serving fewer than 10,000 people, exist across the United States. The pandemic has exacerbated pre-existing challenges for these water systems and for poorer communities faced with rapidly rising water bills, including financial and cyber insecurity, and the rising costs of treating new contaminants in their water and wastewater. The report includes case studies illustrating the breadth and depth of challenges SCWS face due to the COVID-19 pandemic.