Sacramento River

May Revision Trailer Bill Proposals on the Delta Conveyance Project and Water Quality Control Plans

Legislative Analyst's Office (LAO) | May 27th, 2025

LAO Bottom Line: We recommend deferring action on both proposals, without prejudice. These policy issues do not have budget implications. Deferring action would allow the

LAO Bottom Line: We recommend deferring action on both proposals, without prejudice. These policy issues do not have budget implications. Deferring action would allow the Legislature more time and capacity for sufficient consideration of the potential benefits, implications, and trade-offs. Below, we describe the proposals and note some key issues for the Legislature to keep in mind when it considers these proposals.

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.

Measuring Progress Toward Universal Access to Water and Sanitation in California: Defining Goals, Indicators, and Performance Measures

Pacific Institute | September 15th, 2018

In January 2018, over half a million Californians were served by water utilities that were out of compliance with the Safe Drinking Water Act (SDWA). The worst outbreak o

In January 2018, over half a million Californians were served by water utilities that were out of compliance with the Safe Drinking Water Act (SDWA). The worst outbreak of Hepatitis A in recent memory occurred in 2016-2018 due to open defecation and lack of handwashing facilities for persons experiencing homelessness. California’s tribes continue to face problems of poor housing and water and sanitation service, with two-thirds of tribal communities reporting inadequate home plumbing in 2015.1 And the cost of water has increased for many, particularly among small and medium size systems, with 39 community water systems in the state charging more than $100 a month for 12 CCF of water. In response to the problem, California enacted the Human Right to Water in 2012, declaring that “Every human being has the right to safe, clean, affordable, and accessible water adequate for human consumption, cooking, and sanitary purposes.”

Mercury and Methylmercury in Fish and Water from the Sacramento-San Joaquin Delta: August 2016 – April 2017

San Francisco Estuary Institute (SFEI) | September 3rd, 2018

Monitoring of sport fish and water was conducted by the Delta Regional Monitoring Program (Delta RMP) from August 2016 to April 2017 to begin to address the highest prior

Monitoring of sport fish and water was conducted by the Delta Regional Monitoring Program (Delta RMP) from August 2016 to April 2017 to begin to address the highest priority information needs related to implementation of the Sacramento–San Joaquin Delta Estuary Total Maximum Daily Load (TMDL) for Methylmercury (Wood et al. 2010). Two species of sport fish, largemouth bass (Micropterus salmoides) and spotted bass (Micropterus punctulatus), were collected at six sampling locations in August and September 2016. The length-adjusted (350 mm) mean methylmercury (measured as total mercury, which is a routinely used proxy for methylmercury in predator fish) concentration in bass ranged from 0.15 mg/kg or parts per million (ppm) wet weight at Little Potato Slough to 0.61 ppm at the Sacramento River at Freeport. Water samples were collected on four occasions from August 2016 through April 2017. Concentrations of methylmercury in unfiltered water ranged from 0.021 to 0.22 ng/L or parts per trillion. Concentrations of total mercury in unfiltered water ranged from 0.91 to 13 ng/L. Over 99% of the lab results for this project met the requirements of the Delta RMP Quality Assurance Program Plan, and all data were reportable. This data report presents the methods and results for the first year of monitoring. Historic data from the same or nearby monitoring stations from 1998 to 2011 are also presented to provide context. Monitoring results for both sport fish and water were generally comparable to historic observations. For the next several years, annual monitoring of sport fish will be conducted to firmly establish baseline concentrations and interannual variation in support of monitoring of long-term trends as an essential performance measure for the TMDL. Monitoring of water will solidify the linkage analysis (the quantitative relationship between methylmercury in water and methylmercury in sport fish) in the TMDL. Water monitoring will also provide data that will be useful in verifying patterns and trends predicted by numerical models of mercury transport and cycling being developed for the Delta and Yolo Bypass by the California Department of Water Resources (DWR).

Mercury Contamination from Historical Gold Mining in California

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

Mercury in Every Mix

CALFED | May 1st, 2005

Mercury losses and recovery during a suction dredge test in the South Fork of the American River

California State Water Resources Control Board (SWRCB) | July 29th, 2005

Mercury has been used widely since the dawn of recorded history for gold mining. During California’s gold rush, gold miners used about 6 million kilograms or 6.6 thousa

Mercury has been used widely since the dawn of recorded history for gold mining. During California’s gold rush, gold miners used about 6 million kilograms or 6.6 thousand tons of mercury (Churchill, 2000) to recover over 3.6 thousand tons of gold (Bulletin 193). The weight of mercury used is roughly equal to the total weight of a 9-mile long line of 2,750, full sized pickup trucks (note: the pick up truck line equaling gold recovered would only be 5 miles long). The miners lost about half of the mercury to the environment. Using historical records,Churchill (2000) estimated that total mercury losses ranged between 2.3 million and 2.6 million kilograms for placer and lode mining in the Sierra Nevada Geomorphic Province. Consequently, elemental mercury from the gold rush is still found, sometimes in amounts that constitute a local hotspot (i.e., a location where visible elemental mercury is found) in Sierra Nevada watersheds where gold mining occurred. In March 2003, a recreational gold miner reported a mercury hotspot in the South Fork of the American River near Coloma, to State Water Resources Control Board staff. It was the first time a recreational gold miner had revealed a hotspot locations to agency staff. Coloma is California’s historic “Gold Discovery” site as James W. Marshall’s discovery there in January 1848 initiated the 1849 gold rush. Steve Franklin, the recreational gold miner who reported the hotspot, claimed to have recovered about a kilogram of mercury while gold mining from the hotspot during January and February 2003. Finding a hotspot near Coloma raised questions about its potential threat to human health, effects on local fi sh, and threat to water quality. Moreover, its discovery presented an opportunity to test the notion that recreational gold miners effectively clean up mercury hotspots while suction dredging for gold. There is no record of any attempts by state or federal agencies to clean up a mercury hotspot in a California river. But State and federal agencies have discussed whether encouraging or even providing support for recreational gold miners to clean up hotspots is viable and wise. The pros are that there is a potentially large, volunteer workforce. The cons are that oversight would be difficult and, up to now, no data supported the notion that suction dredges could recover mercury efficiently. Recreational gold dredging on public and private lands is a moderately popular activity in California. The Department of Fish and Game (DFG) issues several thousand permits annually to recreational gold dredgers. Along with gold, recreational dredgers recover iron (nails bolts, etc.), lead (fishing weights, buckshot, and spent bullets) and mercury (elemental mercury, mercury/gold amalgam, and mercury stained gold). Over the past several years, United States Forest Service (USFS), Bureau of Land Management (BLM) and State agency staff have discussed setting up a mercury recovery program for recreational dredgers. Incentives (e.g., cash for mercury, free dredging permits, new areas opened for dredging) were proposed in exchange for mercury turned in by recreational dredgers. Offering such incentives was and remains controversial for a variety of reasons and a mercury recovery program was not started. Moreover, an important drawback was that the efficiency of a standard suction dredge at recovering mercury was unknown. Consequently, no one knew if mercury would be lost along with waste sediment from a suction dredge. Clearly, a mercury recovery program that dispersed elemental mercury back into a stream in substantial amounts would be unacceptable. The hotspot presented an opportunity to determine the mercury recovery efficiency of a suction dredge. Studying the hotspot may also reveal bedrock characteristics and sediment transport conditions that cause hotspots, and the effects that concentrated mercury has on local fish. This report documents the results of a suction dredge test that was completed in September 2003 by State Water Board, USFS, and DFG staff.

Meteorological and geographical factors associated with dry lightning in central and northern California

Environmental Research: Climate (IOP) | August 8th, 2022

Lightning occurring with less than 2.5 mm of rainfall—typically referred to as ‘dry lightning’—is a major source of wildfire ignition in central and northern Cali

Lightning occurring with less than 2.5 mm of rainfall—typically referred to as ‘dry lightning’—is a major source of wildfire ignition in central and northern California. Despite being rare, dry lightning outbreaks have resulted in destructive fires in this region due to the intersection of dense, dry vegetation and a large population living adjacent to fire-prone lands. Since thunderstorms are much less common in this region relative to the interior West, the climatology and drivers of dry lightning have not been widely investigated in central and northern California. Using daily gridded lightning and precipitation observations (1987–2020) in combination with atmospheric reanalyses, we characterize the climatology of dry lightning and the associated meteorological conditions during the warm season (May–October) when wildfire risk is highest. Across the domain, nearly half (∼46%) of all cloud-to-ground lightning flashes occurred as dry lightning during the study period. We find that higher elevations (>2000 m) receive more dry lightning compared to lower elevations (

Meteorological driving forces of reference evapotranspiration and their trends in California

Science of the Total Environment (Elsevier) | August 13th, 2022

Reference evapotranspiration (ETo) is a variable that helps determine atmospheric pressure on living (reference) grass to release water into the atmosphere. For this purp

Reference evapotranspiration (ETo) is a variable that helps determine atmospheric pressure on living (reference) grass to release water into the atmosphere. For this purpose, four main driving forces: air temperature, air humidity, solar radiation, and wind speed need to be measured over the well-watered reference grass. The relative influence of these driving forces is region and climate-specific, with daily and seasonal variations. A clear understanding of the dynamic interactions of ETo's driving factors can illuminate the water and energy cycles of the earth and assist modelers with more accurate predictions of ETo. In this study, Pearson correlation, mutual information, and random forest feature importance analyses have been used to evaluate the relative importance of meteorological driving forces of ETo in California. To better understand the interrelations of these variables, 1,365,823 daily data samples from 237 standardized weather stations for 36 years have been clustered into homogeneous climatic zones and analyzed. To compensate for the effects of seasonality, feature importance analysis is also conducted on seasonal and monthly clustered data. Moreover, seasonal and annual trends of ETo and its driving factors are investigated for California and homogeneous zones using the Mann-Kendall test. Our findings reveal that for annually clustered data, solar radiation is the most influential driving factor of ETo in California. However, analysis of seasonal and monthly clustered data shows that vapor pressure deficit is the most informative factor during the summer and spring, while solar radiation is more important during the colder seasons. Results of trend analysis don't suggest a consistent monotonic trend for ETo and other variables for different seasons and zones. However, it is shown that agricultural regions with heavy irrigation dependence like the Central Valley are getting warmer and drier, especially during the irrigation season. This can adversely affect the water resources, agriculture industry, and food production of California, and modeling efforts like this can be very informative for future water resources management.

Methodology for Flow and Salinity Estimates in the Sacramento-San Joaquin Delta and Suisun Marsh

California Department of Water Resources (DWR) | June 15th, 2022

This is the 43rd annual progress report of the California Department of Water Resources’ San Francisco Bay-Delta Evaluation Program, which is carried out by the Delta M

This is the 43rd annual progress report of the California Department of Water Resources’ San Francisco Bay-Delta Evaluation Program, which is carried out by the Delta Modeling Section. This report is submitted annually to the State Water Resources Control Board pursuant to its Water Right Decision D-1485, Term 9, which is still active pursuant to its Water Right Decision D-1641, Term 8. This report documents progress in the development and enhancement of computer models for the Delta Modeling Section of the Bay-Delta Office. It also reports the latest findings of studies conducted as part of the program. This report was compiled under the direction of Nicky Sandhu, Program Manager for the Bay-Delta Evaluation Program.