Effects of water management on the wetlands of the Colorado River Delta, Mexico

Conservation Biology (Society for Conservation Biology) | August 1st, 1996

The lower delta of the Colorado River has been severely affected by the upstream diversion of water for human use. No river water is officially appropriated to support de

The lower delta of the Colorado River has been severely affected by the upstream diversion of water for human use. No river water is officially appropriated to support delta wetlands, yet large marsh areas of conservation interest still exist below the agricultural fields in Mexico. These are supported by flood water, agricultural drainage water, municipal sewage effluent, and seawater in the intertidal zone. From 1973 to 1993 the area of freshwater and brackish marsh varied widely, from 5800 to 63,000 ha. A new opportunity exists to restore wetlands in the delta now that the upstream water impoundments on the Colorado River are filled and flood flows are once again being directed to the delta. But flood control structures now channel most of the flood water directly to the sea, and most of the effluent waters are deposited in evaporation basins rather than used to support wetlands. If the Yuma Desalting Plant in the United States becomes operational and if the Rio Hardy wetlands continue to be drained, the area of brackish wetlands could decrease to less than 2000 ha in the near future. Preserving the remaining wetlands will require a binational water management plan. The plan should maximize the benefits to wetlands of flood and irrigation return flows that enter the delta, and it should minimize flood risks.

Estuary News, April 1995

San Francisco Estuary Partnership (SFEP) | April 15th, 1995

High-Salinity Sensitivity Study: Short-and Long-Term Exposure Assessments

California State Water Resources Control Board (SWRCB) | April 12th, 2013

The West Basin Municipal Water District (WBMWD) High Salinity Sensitivity Study (HSS Study) comprehensively evaluated the potential short-term and long-term exposure effe

The West Basin Municipal Water District (WBMWD) High Salinity Sensitivity Study (HSS Study) comprehensively evaluated the potential short-term and long-term exposure effects of high salinity discharges from the WBMWD ocean water desalination demonstration facility (OWDDF) on aquatic organisms representative of communities indigenous to various near shore environments in Southern California. Short-term effects were evaluated using Whole Effluent Toxicity (WET) bioassays developed by the U.S. Environmental Protection Agency (USEPA) to quantify the magnitude and threshold of potential biological effects of discharges (e.g. treated wastewater). Both acute toxicity (mortality effects) and chronic toxicity (mortality + sublethal effects) bioassays were performed by a state accredited bioassay laboratory. Long-term effects were evaluated using mesocosm procedures performed at the OWDDF by exposing multiple organisms for eight weeks to ambient seawater and diluted brine flows from the OWDDF in large aquaria constructed to simulate the OWDDF discharge environment.

Identification of fresh submarine groundwater off the coast of San Diego, USA, using electromagnetic methods

Hydrogeology Journal (Springer) | March 1st, 2022

Climate change has a pronounced effect on water resources in many semiarid climates, causing populated areas such as San Diego County (USA), to become more vulnerable to

Climate change has a pronounced effect on water resources in many semiarid climates, causing populated areas such as San Diego County (USA), to become more vulnerable to water shortages in the coming decades. To prepare for decreased water supply, San Diego County is adopting policies to decrease water use and to develop additional local sources of water. One new local source of freshwater is produced by a desalination facility that purifies brackish groundwater from the coastal San Diego Formation. This formation has been studied extensively onshore, but little is known about the geology or groundwater quality offshore in the adjacent continental shelf. Because most groundwater systems are interconnected and complex, further analysis is needed to identify offshore geology, possible sequestration of freshwater in the shelf, and potential pathways for saltwater intrusion. This comprehensive understanding is important because seawater intrusion may limit use of the San Diego Formation and longevity of desalination facilities. Controlled-source electromagnetic methods are uniquely suited to detecting offshore groundwater as they are sensitive to changes in pore fluids such as the transition from fresh to brackish groundwater. This paper describes results from surface-towed electromagnetic surveys that mapped the pore-fluid salinity and possible fluid pathways in the continental shelf off the coast of San Diego. The results indicate a considerable volume of fresh-to-brackish groundwater sequestered in the shelf, both in continuous lenses and isolated pockets, that appear influenced by fault systems and shallow stratigraphy.

Integrated Coastal Groundwater Monitoring Program and Plan

Monterey County Water Resources Agency (MCWRA) | May 19th, 2019

California American Water Company (CalAm) is working to increase sustainability of their water supply portfolio to meet the long-term needs of customers in their

California American Water Company (CalAm) is working to increase sustainability of their water supply portfolio to meet the long-term needs of customers in their service area on the Monterey Peninsula. Accordingly, CalAm has proposed the Monterey Peninsula Water Supply Project (MPWSP). The MPWSP includes a desalination plant, distribution pipelines, aquifer storage and recovery and in-lieu use of desalinated water. Feedwater for the desalination plant would be from a seawater intake system consisting of slant wells constructed into the shallow aquifers at the coastal margin of the Salinas Valley Groundwater Basin (SVGB). The objective of the MPWSP is to meet CalAm’s long-term water demands and comply with state imposed regulatory requirements1. A MPWSP Test Slant Wells Study (HWG, 2017) was conducted to evaluate project effects and support preparation of a draft and Final Environmental Impact Statement/Environmental Impact Report (EIR/EIS) (ESA, 2017). CalAm has received a Certificate of Public Convenience and Necessity CPCN) for the MPWSP from the California Public Utilities Commission (CPUC)2. The EIR/EIS supported the CPUC decision. This document presents a proposed Coastal Monitoring Plan (Monitoring Plan) to continue observing the MPWSP effects, if any, on the SVGB.

Key Issues in Seawater Desalination in California: Costs and Financing

Pacific Institute | November 27th, 2012

Economics – including both the cost of the water produced and the complex financial arrangements needed to develop a project – are key factors that will determine the

Economics – including both the cost of the water produced and the complex financial arrangements needed to develop a project – are key factors that will determine the ultimate success and extent of desalination in California. New research from the Pacific Institute, Key Issues for Seawater Desalination in California: Cost and Financing, assesses desalination costs, financing, and risks associated with desalination projects. The Pacific Institute analysis finds that the cost to produce water from a desalination plant is high but subject to significant variability, with recent estimates for plants proposed in the state ranging from $1,900 to more than $3,000 per acre-foot. “Seawater desalination remains among the most expensive water-supply options available, although the public and decision-makers must exercise caution when comparing costs among different projects,” said Heather Cooley, co-director of the Pacific Institute Water Program and lead author of the report. “In some cases, costs are reported in ways that are not directly comparable. For example, some report the cost of the desalination plant alone, while others include the cost for additional infrastructure needed to integrate the desalination plant into the rest of the water system. Some estimates include costs to finance the project, while others don’t. Even when there is an apples-to-apples comparison, there are a number of site- and project-specific factors that make cost comparisons difficult, such as energy, land, and labor costs and the availability of visible and hidden subsidies.” Key Issues for Seawater Desalination in California: Cost and Financing is part of a series of research reports in progress that identify key outstanding issues that must be addressed before additional proposals for new seawater desalination in California are approved. Other issues addressed include the environmental impacts of seawater desalination, the cost and financing of proposed projects, and energy requirements and their greenhouse gas implications. Our analyses seek to provide communities and decision makers with information needed to make decisions about building desalination plants and to create a more rational and sustainable policy around seawater desalination along the California coast, and elsewhere.

Key Issues in Seawater Desalination in California: Energy and Greenhouse Gas Emissions

Pacific Institute | May 1st, 2013

Interest in seawater desalination in California is high, with 17 plants proposed along the California coast and two in Mexico. But removing the salt from seawater is an e

Interest in seawater desalination in California is high, with 17 plants proposed along the California coast and two in Mexico. But removing the salt from seawater is an energy-intensive process that consumes more energy per gallon than most other water supply and treatment options. A new report from the Pacific Institute series Key Issues for Seawater Desalination in California describes the energy requirements and associated greenhouse gas emissions for desalinated water and evaluates the impact of short- and long-term energy price variability on the cost of desalinated water. Energy requirements are key factors that will impact the extent and success of desalination in California. Key Issues for Seawater Desalination in California: Energy and Greenhouse Gas Emissions shows energy requirements for seawater desalination average about 15,000 kWh per million gallons of water produced. By comparison, the least energy-intensive options of local sources of groundwater and surface water require 0 – 3,400 kWh per million gallons; wastewater reuse, depending on treatment levels, may require from 1,000 – 8,300 kWh per million gallons; and energy requirements for importing water through the State Water Project to Southern California range from 7,900 – 14,000 kWh per million gallons. “Beyond the electricity required for the desalination facility itself, producing any new source of water, including through desalination, increases the amount of energy required to deliver and use the water produced as well as collect, treat, and dispose of the wastewater generated,” said Heather Cooley, co-director of the Pacific Institute Water Program and report author. Conservation and efficiency, by contrast, can help meet the anticipated needs associated with growth while maintaining or even reducing total energy use and greenhouse gas emissions.” Desalination is a reliable source of water, which can be especially valuable during a drought. However, building a desalination plant may reduce a water utility’s exposure to water reliability risks at the added expense of an increase in exposure to energy price risk. Energy is the largest single variable cost for a desalination plant, varying from one-third to more than one-half the cost of produced water. Because of its high energy use, desalination creates or increases the water supplier’s exposure to energy price variability.

Key Issues in Seawater Desalination in California: Marine Impacts

Pacific Institute | December 11th, 2013

Desalination, like other major industrial processes, has environmental impacts that must be understood and mitigated. A new report from the Pacific Institute examines e

Desalination, like other major industrial processes, has environmental impacts that must be understood and mitigated. A new report from the Pacific Institute examines effects on the marine environment associated with the construction and long-term operation of seawater desalination plants, including withdrawing water from the ocean and discharging the highly concentrated brine. “If and when we build plants in California, we must ensure that the plants are built to the highest standards given what we know now,” said Cooley. “Additionally, monitoring of existing and proposed desalination plants is crucial to improving our understanding of the sensitivity of the marine environment and helping promote more effective operation and design to minimize ecological and biological impacts in the future.” Modern reverse-osmosis desalination plants, such as those planned or proposed on the California coast, take in large volumes of seawater – generally two gallons are withdrawn for every gallon of freshwater produced – and pass it through fine-pored membranes to separate freshwater from salt. The highly concentrated brine is then typically disposed of back into the ocean. With the majority of desalination plants extracting water directly through open water intakes in the ocean, there is a direct impact on marine life. Fish and other marine organisms are killed on the intake screens (impingement); organisms small enough to pass through, such as plankton, fish eggs, and larvae, are killed during processing of the salt water (entrainment). The impacts on the marine environment, even for a single desalination plant, may be subject to daily, seasonal, annual, and even decadal variation, and are likely to be species- and site-specific.

Management of Brine Discharges to Coastal Waters: Recommendations of a Science Advisory Panel

Southern California Coastal Water Research Project | June 6th, 2012

A panel of five experts in diverse fields related to brine disposal in the ocean was convened to advise the State Water Resources Control Board on best practices for brin

A panel of five experts in diverse fields related to brine disposal in the ocean was convened to advise the State Water Resources Control Board on best practices for brine disposal in support of the development of an amendment to the Ocean Plan. The brine concentrates can result from desalination of brackish groundwater, recycling domestic wastewater, and especially desalination of seawater. The potential of seawater desalination to provide potable water in the state is growing rapidly, with many plants currently proposed or in the planning stage. The state presently has no regulations on brine discharges and each plant is considered on a case-by-case basis. The panel reviewed extensive material, including peer-reviewed journal articles, articles in the gray literature, NPDES permits that have been issued, various regulations from around the world, and results of monitoring studies, and heard presentations about experience with operating discharges. From these reviews it is apparent that concentrate can be disposed of with minimal environmental effects if properly executed. Desirable methods of discharge include co-disposal with heated cooling water from power plants or domestic wastewater, or from a multiport diffuser if “pure” brine is released. Discharges with rapid initial dilution into areas of good flushing result in impacts that extend only a few tens of meters from the discharge. Conversely, poorly implemented disposal schemes with low initial dilution in poorly flushed areas can cause widespread alterations of community structure in seagrass, coral reef, and soft-sediment systems.

Mitigation and Fees for the Intake of Seawater by Desalination and Power Plants

California State Water Resources Control Board (SWRCB) | March 4th, 2012

Raw seawater is used for a variety of purposes, including as source water for desalination plants and to cool coastal power plants. Raw seawater is, however, not just col

Raw seawater is used for a variety of purposes, including as source water for desalination plants and to cool coastal power plants. Raw seawater is, however, not just cold and salty but an ecosystem that contains diverse and abundant organisms including the young stages of numerous invertebrates and fishes. Whether impinged (large individuals stuck on screens prior to entering the plant or killed during other plant processes such as heat treatment) or entrained (small individuals carried into the plant with the water) the organisms are killed, essentially eliminating the living production in the water used (review in York and Foster 2005). Considerable research has have been done in California to better estimate losses to this ecosystem by coastal power plant intakes (York and Foster 2005, Steinbeck et al. 2007), and to determine how these losses can be mitigated (Strange et al. 2004).  The information from this research has contributed to State of California policy regulating water used by power plants.  The policy now applies only to power plants but the intent to protect marine organisms is also broadly applicable to desalination plants and other users of large volumes of seawater. The State’s Once-through Cooling Policy (Policy) states that plants must implement measures to mitigate interim impacts occurring after October 1, 2015, and until the plant comes into full compliance through conversion to closed cycle cooling or by using operational controls and/or structural control technology that results in comparable reductions in impingement and entrainment (IM&E).