Managing California’s Water: From Conflict to Reconciliation

Public Policy Institute of California (PPIC) | April 5th, 2011

In this book, we explore solutions for the modern era, when water management must become more balanced and flexible to support both economic prosperity and environmental

In this book, we explore solutions for the modern era, when water management must become more balanced and flexible to support both economic prosperity and environmental sustainability. We start by reviewing the history of how California has adapted to changes and conflicts in water management in the past—slowly, controversially, and imperfectly—but with remarkable success. We then lay out a variety of promising principles and directions for improving water management in California for contemporary and anticipated future conditions.

Managing Freshwater Discharge to the San Francisco Bay/Sacramento-San Joaquin Delta Estuary―The Scientific Basis for an Estuarine Standard

San Francisco Estuary Project | October 26th, 1992

Aquatic resources of the Sacramento-San Joaquin Delta and upper portions of San Francisco Bay have undergone significant declines over the past several decades. Species c

Aquatic resources of the Sacramento-San Joaquin Delta and upper portions of San Francisco Bay have undergone significant declines over the past several decades. Species characteristic of the Delta and rivers, such as striped bass and salmon, began to decline during the late 1970s. Prolonged drought, large diversions of fresh water, and dramatic increases in populations of introduced aquatic species during the 1980s and 1990s brought a number of indigenous aquatic species to extremely low levels. Species that spend more of their lives downstream of the Delta, including Delta smelt, longfin smelt, and many zooplankton, maintained large populations through the 1970s, but declined sharply after the mid-1980s. Declines in aquatic resources have led to curtailed fishing seasons, to petitions for endangered species status, and general concern about the health of the estuarine ecosystem.

Managing Surface Water-Groundwater to Restore Fall Flows in the Cosumnes River

American Society of Civil Engineers (ASCE) | June 15th, 2004

Declining fall flows are limiting the ability of the Cosumnes River to support large fall runs of Chinook salmon. Management scenarios linking surface water and g

Declining fall flows are limiting the ability of the Cosumnes River to support large fall runs of Chinook salmon. Management scenarios linking surface water and groundwater alternatives to provide sufficient fall flows are examined using groundwater flow and channel routing models. Results show that groundwater overdraft in the basin has converted the river to a predominantly losing stream, practically eliminating base flows. Management alternatives to increase net recharge for example, pumping reductions were examined along with surface water augmentation options. Using a minimum depth standard for fish passage, average surface water flow deficits were computed for the migration period of Chinook salmon. Groundwater deficits were evaluated by comparing simulated current groundwater conditions with conditions under various scenarios. Increases in net recharge on the order of 200 to 300 million m3/year would be required to reconnect the regional aquifer with the channel and in turn reestablish perennial base flows. Options that combine surface water augmentation with groundwater management are most likely to ensure sufficient river flows in the short term and to support long-term restoration of regional groundwater levels.

Managing to End Groundwater Overdraft in California’s Central Valley with Climate Change

University of California, Davis (UC Davis) | July 14th, 2016

Several water management cases with climate change are modeled to assess the effects of ending long-term groundwater overdraft in the Central Valley using the Cal

Several water management cases with climate change are modeled to assess the effects of ending long-term groundwater overdraft in the Central Valley using the California Value Integrated Network (CALVIN) model, a hydro-economic optimization model of California’s water system. CALVIN optimizes water management decision-making for the lowest net operating and water scarcity cost over an 82-year period of unimpaired inflows. Recent updates to the CALVIN model include, input hydrology, network representation, agricultural demand and shortage penalties, and hydropower improvements. Management cases evaluated include changes in outflow and inflow requirements for the Sacramento-San Joaquin Delta (Delta), and prohibiting long-term groundwater overdraft. Cases were analyzed over an 82-year modified historical record with a warmer, drier climate, and compared to historical hydrology results. A modelled warmer, drier climate reduces average inflows overall by about 28% and shifts stream flows towards winter and away from spring. Results show large water scarcities south of the Delta without Delta exports, especially for agriculture. Allowing for increased water transfers, Delta exports, conjunctive use, and water recycling and desalination reduces the water supply effects of groundwater overdraft and climate change.

Mark/Recapture Experiments at Clifton Court Forebay to Estimate Pre-Screening Loss to Juvenile Fishes: 1976-1993

California Department of Fish and Wildlife (CDFW) | September 30th, 1997

From October 1976 through November 1993, the California Department of Fish and Game conducted mark/recapture experiments at Clifton Court Forebay, designed to estimate pr

From October 1976 through November 1993, the California Department of Fish and Game conducted mark/recapture experiments at Clifton Court Forebay, designed to estimate pre-screen loss to entrained juvenile fishes. Ten studies were conducted; eight evaluated losses to hatchery-reared juvenile chinook salmon, and two evaluated losses to hatchery-reared juvenile striped bass. Pre-screen loss was calculated from the proportion of marked fish released at the radial gates that were subsequently recaptured during salvage operations at Skinner Fish Facility. The proportion was adjusted for handling mortality, fish facility louver effiCiency, and any subsampling at the facility. Studies were conducted across a wide range of environmental conditions and State Water Project operations, with a wide range in the size ofexperimental fish. Pre-screen loss estimates for juvenile chinook salmon were 63-99%. Potential biases in estimates of pre-screen loss may be due to (1) the calculation for pre-screen loss, (2) underrepresentative and over-representative salvage of experimental fish at Skinner Fish Facility, and (3) the introduction of experimental fish directly into Clifton Court Forebay. A multiple-regression analysis of pre-screen loss to juvenile salmon showed that 91% of the variance in pre-screen loss can be explained by export rate, experimental fish size, and water temperature. 

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.

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.

Memo: Issues Related to Overlap between Pre-1914 and Riparian Water Right Claims in the Delta

California State Water Resources Control Board (SWRCB) | December 15th, 2017

To: Michael Patrick George, Delta Watermaster From: Micah Green, Water Rights Analyst Re: Issues Related to Overlap between Pre-1914 and Riparian Water Right Claims in

To: Michael Patrick George, Delta Watermaster From: Micah Green, Water Rights Analyst Re: Issues Related to Overlap between Pre-1914 and Riparian Water Right Claims in the Delta Date: December 15, 2017 Pursuant to your request, I have researched an issue raised in the course of my review of responses to the Division of Water Rights’ 2015 Information Order submitted by water right claimants within the Legal Delta. I. Question Presented Under California water law and within the Legal Delta, are there any circumstances under which riparian and appropriative rights can “overlap” becoming indistinguishable or inseparable such that either or both may be lawfully exercised at the election of the holder? II. Short Answer It is possible to perfect both riparian and appropriative water rights for beneficial use on the same parcel. However, riparian and appropriative rights are distinct property interests that must be separately established. There is no California precedent recognizing “overlapping” or “intertwined” water rights, and water laws against hoarding and non-use operate to preclude the duplicative exercise of water rights.

Mercury Contamination from Historical Gold Mining in California

U.S. Geological Survey (USGS) | October 31st, 2005

Mercury in Every Mix

CALFED | May 1st, 2005