The Delta Plan: Ensuring a reliable water supply for California, a healthy Delta ecosystem, and a place of enduring value

Delta Stewardship Council (Delta Council) | May 16th, 2013

The Sacramento-San Joaquin River Delta is the grand confluence of California’s waters, the place where the state’s largest rivers merge in a web of channels—and in

The Sacramento-San Joaquin River Delta is the grand confluence of California’s waters, the place where the state’s largest rivers merge in a web of channels—and in a maze of controversy. The Delta is a zone where the wants of a modern society come into collision with each other and with the stubborn limitations of a natural system. In 2009, seeking an end to decades of conflict over water, the Legislature established the Delta Stewardship Council with a mandate to resolve long-standing issues. The first step toward that resolution is the document you have before you, the Delta Plan.

The Economic Impacts of Central Valley Salinity

California State Water Resources Control Board (SWRCB) | March 20th, 2009

The study team was charged with measuring the economic impacts of increasing salinity in the Central Valley to the year 2030. The study was conducted assuming that there

The study team was charged with measuring the economic impacts of increasing salinity in the Central Valley to the year 2030. The study was conducted assuming that there is no change in current policy and, as such, represents the economic impacts associated with taking no action. Additionally, the study was conducted on an aggregate valley-wide basis that required averaging the effects of salinity and, in some cases, costs. The growth in salinity in the Central Valley was based on two factors. The first factor was the growth of the areas of shallow saline groundwater based on 30 years of historical records. The second factor was increased levels of salts that result indirectly from imported water. Based on increasing salinity stemming from these factors, the direct economic effects on industry, residential, food processing, confined animal operations, and irrigated agricultural production in the Central Valley were measured. Economic and physical effects were quantified using different physical and economic models. In addition, the team undertook a substantial survey of the population in the Central Valley to establish non-market values for increased salinity and its effect on non-market activities. The study results showed that if salinity increases at the current rate until 2030, the direct annual costs will range from $1 billion to $1.5 billion. Total annual income impacts to California will range between $1.7 billion to $3 billion by 2030. The income impacts to the Central Valley will range between $1.2 billion and $2.2 billion.  The production of goods and services in California could be reduced from $5 billion to $8.7 billion a year. The Central Valley output reduction would range between $2.8 billion to $5.3 billion. Furthermore, there is $145 million per year of non-market costs. In terms of job losses the increase in salinity by 2030 could cost the Central Valley economy 27,000 to 53,000 jobs. California could lose 34,000 to 64,000 jobs. In short, the problem is substantial and growing steadily. The magnitude of the economic and employment losses justifies a more detailed study of remedial action and correction policies.

The Sacramento-San Joaquin Delta: The Evolution and Implementation of Water Policy: An Historical Perspective

University of California, Davis (UC Davis) | June 1st, 1977

This report is a history of the attempts to control the encroachment of salinity from San Francisco Bay into the Delta of the Sacramento and San Joaquin rivers from 1920

This report is a history of the attempts to control the encroachment of salinity from San Francisco Bay into the Delta of the Sacramento and San Joaquin rivers from 1920 to the present. Two basic solutions to the problem present themselves: the physical separation of salt water from fresh water by means of a barrier at some point downstream from the Delta, or the release of sufficient water from upstream storage reservoirs to drive back tidal salinity.

The Salinity of Rivers

Scientific American | July 1st, 1981

Many ancient civilizations rose by diverting rivers and irrigating arid lands to grow crops. For such projects to succeed human beings had to learn to work cooperativ

Many ancient civilizations rose by diverting rivers and irrigating arid lands to grow crops. For such projects to succeed human beings had to learn to work cooperatively toward a common objective. The most fruitful of the ancient systems was created at the southeastern end of the Fertile Crescent, the broad valley formed by the Tigris and the Euphrates in what is now Iraq. From there civ il ization spread eastward through present-day Iran, Afghanistan, Pakistan, India and thence into China, wherever rivers disgorged through valleys of recently deposited alluvial soil. At its peak of productivity each irrigated region probably supported well over a million people. All these civilizations ultimately collapsed, and for the same reason: the land became so salty that crops could no longer be grown on it. The salts that were washed out of the soil at higher elevations became concentrated in the irrigated fields as the water evaporated from the surface and transpired through the leaves of the growing crops. Although floods, plagues and wars took their toll, in the end the civilizations based on irrigation faded away because of salination.

The tradeoff between water savings and salinization prevention in dryland irrigation

Advances in Water Resources (Elsevier) | December 7th, 2023

Soil salinization is a global phenomenon that affects large tracts of arid farmland worldwide. It contributes to the loss of soil fertility, declining yields, and – in

Soil salinization is a global phenomenon that affects large tracts of arid farmland worldwide. It contributes to the loss of soil fertility, declining yields, and – in the most severe cases – land unsuitability for cultivation. Irrigation water applications are both the main cause of and the solution to, anthropogenic (or ‘secondary’) salinization because salt typically enters the soil column as dissolved in irrigation water and leaves it through excess water applications (e.g., leaching). Excess leaching, which places additional water costs in areas affected by water scarcity, can be achieved with different irrigation techniques and practices. Here, by complementing a process-based crop water model with a salt balance of the shallow soil, we investigate the tradeoff between root zone salinization and water conservation to limit withdrawals from the water source. We evaluate how such a tradeoff is achieved under different irrigation technology and excess leaching practices. Considering as a case study the cultivation of tomatoes in Egypt, we find that drip and furrow irrigation allows for better control of salt accumulation, thus preventing crop exposure to salt stress. Drip irrigation achieves this goal with minimal water applications because it maintains the soil wetter. Thus, the (rare) rainfall events find more suitable conditions to drain the excess moisture. Conversely, by using more irrigation water (and ‘less efficiently’), furrow irrigation allows for higher rates of soil drainage and salt leaching. The irrigation schedule typically adopted with sprinkler irrigation allows for soil drying, thus limiting the ability of rainfall events to drain the soil and leach its salts. Collectively, these results highlight the key role of irrigation technology and practices in the management of secondary salinity in dryland agriculture. Specifically, there is a tradeoff between minimizing water use and preventing salt accumulation in the root zone. Drip irrigation exhibits the co-benefit of achieving both goals, while furrow irrigation limits soil salinity at the cost of requiring greater volumes of applied irrigation water.

Time-lagged impacts of extreme, multi-year drought on tidal salt marsh plant invasion

Ecological Society of America (ESA) | June 11th, 2020

Climate change is projected to increase the frequency of extreme drought events, which can have dramatic consequences for ecosystems. Extreme drought may interact with o

Climate change is projected to increase the frequency of extreme drought events, which can have dramatic consequences for ecosystems. Extreme drought may interact with other stressors such as invasion by non-native species, yet little research has explored these dynamics. Here, we examine the physical mechanisms and temporal scale underlying a dieback of an invasive non-native plant, Lepidium latifolium, in tidal salt marshes of the San Francisco Bay, California, USA, during an extreme, multi-year drought occurring from 2012 to 2015. Using generalized additive mixed models (GAMMs), we explored the relationship between eight years of estuarine salinity data and five years of L. latifolium density data from three marshes spanning a gradient of salinity across the San Francisco Bay. We found a significant time-lagged (3 yr) effect of estuarine salinity on L. latifolium density, with high salinities preceding reductions in L. latifolium densities and low salinities preceding increases. The most dramatic change in stem density, a 54% reduction in 2015, was preceded by a salinity increase of 43% from 2011 to 2012. We found the L. latifolium decline was driven by impacts on mature, rather than young, plants. Additionally, we tested the importance of local precipitation in driving L. latifolium densities in a one-season rain exclusion experiment. We found 100% exclusion of precipitation during one rainy season (January–mid-May) did not have a significant impact on densities of mature stands of L. latifolium. Our finding that estuarine salinity was a key driver of L. latifolium invasion dynamics suggests sea level rise, like extreme drought, may hinder L. latifolium invasion, as it will also raise estuarine salinities. Further, our study highlights the importance of temporal lags in understanding climate change impacts on biological invasions, which has received very little study to date.

Torres Martinez Tribe Salton Sea Oral Testimony

Salton Sea Authority | September 24th, 2020

 Chairman and Ranking Member, I sincerely appreciate the opportunity to testify today. I am the Tribal Council Chairman of the Torres Martinez Desert Cahuilla (Tribe) an

 Chairman and Ranking Member, I sincerely appreciate the opportunity to testify today. I am the Tribal Council Chairman of the Torres Martinez Desert Cahuilla (Tribe) and a director on the Salton Sea Authority (SSA). I offer this testimony on behalf of both the Tribe and SSA.  I want to begin by thanking Congressman Ruiz (D-Calif.) and Congressman Vargas (D-Calif.) for their hard work to place this issue squarely before the Committee today. The Tribe and SSA view this hearing as a very important beginning of a more robust Congressional effort to drive federal action at the Salton Sea. 

Total Water Management Study for the Central Valley Basin, California, Interim Water Supply Working Document No. 9

U.S. Bureau of Reclamation (USBR) | March 1st, 1976

Transboundary geophysical mapping of geological elements and salinity distribution critical for the assessment of future sea water intrusion in response to sea level rise

European Geosciences Union (EGU) | July 4th, 2012

Geophysical techniques are increasingly being used as tools for characterising the subsurface, and they are generally required to develop subsurface models that properly

Geophysical techniques are increasingly being used as tools for characterising the subsurface, and they are generally required to develop subsurface models that properly delineate the distribution of aquifers and aquitards, salt/freshwater interfaces, and geological structures that affect groundwater flow. In a study area covering 730 km2 across the border between Germany and Denmark, a combination of an airborne electromagnetic survey (performed with the SkyTEM system), a high-resolution seismic survey and borehole logging has been used in an integrated mapping of important geological, physical and chemical features of the subsurface. The spacing between flight lines is 200–250 m which gives a total of about 3200 line km. About 38 km of seismic lines have been collected. Faults bordering a graben structure, buried tunnel valleys, glaciotectonic thrust complexes, marine clay units, and sand aquifers are all examples of geological structures mapped by the geophysical data that control groundwater flow and to some extent hydrochemistry. Additionally, the data provide an excellent picture of the salinity distribution in the area and thus provide important information on the salt/freshwater boundary and the chemical status of groundwater. Although the westernmost part of the study area along the North Sea coast is saturated with saline water and the TEM data therefore are strongly influenced by the increased electrical conductivity there, buried valleys and other geological elements are still revealed. The mapped salinity distribution indicates preferential flow paths through and along specific geological structures within the area. The effects of a future sea level rise on the groundwater system and groundwater chemistry are discussed with special emphasis on the importance of knowing the existence, distribution and geometry of the mapped geological elements, and their control on the groundwater salinity distribution is assessed.

Variations on a method for evaluating decadal-scale changes in the groundwater quality of two GAMA coastal study units 2004–14, California GAMA Priority Basin Project

U.S. Geological Survey (USGS) | August 8th, 2018

Decadal changes in groundwater quality in two study units on the north-central California coast were evaluated by the Priority Basin Project (PBP) of the Groundwater Ambi

Decadal changes in groundwater quality in two study units on the north-central California coast were evaluated by the Priority Basin Project (PBP) of the Groundwater Ambient Monitoring and Assessment (GAMA) Program. Groundwater samples collected from wells during 2004–05 were compared on a pair-wise basis to samples collected from the same wells during 2014. The data set consisted of paired-samples from 50 public supply wells in 2 GAMA-PBP study units (25 wells each in the North San Francisco Bay and the Monterey Bay and Salinas Valley Basins), with analytical results for 160 water-quality constituents. Statistical analysis was done on grouped results for the 59 constituents that were detected in at least 10 percent of the samples during either sampling period to evaluate decadal-scale change by a step-trend analysis. The data for both of the sampling periods were processed three different ways, resulting in three variations of the paired results to be submitted for statistical analyses. The first evaluation method variation processed data only to facilitate comparison of data when one or both of the results was a non-detection. The second and third variations applied the additional requirement that differences between initial and decadal-sample results exceed a defined threshold to prevent small differences from supporting the conclusion of a step trend. One method for setting the difference threshold between initial-sampling and resampling results is based on criteria used by the GAMA-PBP to determine whether or not replicate results are acceptable. The other difference-threshold-setting method uses a calculated confidence interval around each result based on demonstrated analytical variability for the constituents during each sampling period. Finally, constituents for which decadal-scale changes were statistically significant were identified using the Wilcoxon-Pratt signed-rank test on each of the three evaluation method variations. Step trends were identified by at least 1 of the 3 method variations for 33 constituents. After considering other factors, however, such as water-quality context and the results of quality-control samples, it was concluded that decadal changes were meaningful for 14 constituents in at least 1 of the 2 study units. Constituents for which step trends indicated meaningful increases were dissolved oxygen, total nitrogen, nitrate, orthophosphate, calcium, chloride, sulfate, iron, and lithium. Constituents for which step trends indicated meaningful decreases were temperature, arsenic, lead, the isotopic ratio of carbon-13, and tritium.