In 2015, a seawater desalination plant was built at cost of $1 billion. Now, it provides 50 million gallons of drought-proof drinking water daily, but does it harm marine life or raise cost of living?

In 2015, a seawater desalination plant was built at cost of $1 billion. The Claude “Bud” Lewis Carlsbad Desalination Plant was constructed to produce drinking water from seawater for the San Diego region. The facility opened in December 2015 and now produces about 50 million gallons of drinking water each day. The plant supplies about 10% of San Diego County’s total drinking water demand. It gives the region a water source that does not depend on rainfall or imported water supplies. At the same time, the facility has raised questions about water costs, electricity use, greenhouse gas emissions and effects on marine life. The plant was developed under a long-term agreement between the San Diego County Water Authority and Poseidon Water. The agreement was approved in November 2012 and covers water purchases for 30 years.

Why was the Carlsbad desalination plant built?

San Diego County has depended on water brought in from outside the region. That dependence can create problems when imported supplies face shortages or when outside agencies impose restrictions.


The Claude “Bud” Lewis Carlsbad Desalination Plant was built to provide a source of water produced within the region. Seawater is taken into the facility and processed through reverse osmosis filters. The process removes salt and other materials from seawater to produce drinking water.

The plant provides what is described as drought-proof drinking water because its production does not depend on rainfall in the same way as traditional water supplies. The facility also gives the Water Authority more control over part of its water supply. It can reduce the region’s vulnerability to imported water shortages and political restrictions from agencies outside the area.

In 2015, a seawater desalination plant was built at cost of $1 billion

The construction of the plant and its 10-mile pipeline cost close to $1 billion. The pipeline was required to move desalinated seawater from the facility to the Water Authority’s aqueduct system. The project also put about $350 million into the regional economy during construction.

About 2,500 jobs were filled during the construction of the facility. These jobs were connected to the plant and related construction work. The plant began operations in December 2015. Since then, it has remained part of the San Diego region’s water supply system. Its production capacity is linked to the long-term Water Purchase Agreement between the Water Authority and Poseidon Water.

How much water does the plant provide?

The Carlsbad desalination plant produces about 50 million gallons of drinking water each day. The amount represents about 10% of San Diego County’s total drinking water demand. The Water Purchase Agreement approved in November 2012 allowed the Water Authority to purchase up to 56,000 acre-feet of desalinated seawater each year.

An acre-foot is a unit used to measure large amounts of water. It is commonly used by water agencies when discussing supplies and demand. The plant therefore serves as one part of the region’s water supply. It does not replace all other sources of water. Its role is to provide a supply that can continue during periods when other sources face shortages.

What is the Water Purchase Agreement?

In November 2012, the Water Authority approved a 30-year Water Purchase Agreement with Poseidon Water. Under the agreement, Poseidon was responsible for developing and building the desalination plant. The company also built the 10-mile conveyance pipeline that connects the plant with the Water Authority’s aqueduct system.

Poseidon Water is a private, investor-owned company that develops water and wastewater infrastructure. The agreement places certain project risks on the private sector. These include risks linked to the design, construction and operation of the plant.

The Water Authority purchases water from the plant at prices set in advance under the agreement. The agreement also includes requirements for water quality. If the water does not meet the quality requirements specified in the agreement, the Water Authority does not pay for it. The Water Authority also has the right to make sure that the facility is operated and maintained in a safe and efficient manner and according to industry standards.

Does it affect water bills?

The desalination has a direct effect on water costs for local customers. The plant adds about a few dollars per month to the water bill of a typical homeowner. The cost is linked to the price of producing and purchasing desalinated water. The cost of desalination has contributed to San Diego County having some of the highest water rates in California, as per media reports.

Environmental concerns

Desalination requires a large amount of electricity. The Carlsbad facility uses reverse osmosis to separate salt from seawater. The process requires seawater to be pushed through filters under pressure. Electricity is therefore a major part of the plant’s operation. High energy use can also lead to higher greenhouse gas emissions, depending on the source of the electricity used to operate the facility.

Marine life is another issue linked to the desalination process. The plant uses seawater as its source. Water intake systems can trap small marine organisms and fish larvae. Some of these organisms can die during the intake process. The discharge process creates another environmental issue. After salt is removed from seawater, the remaining water contains a higher concentration of salt. This byproduct is known as hyper-saline brine.

The release of brine into the marine environment can affect local water conditions. The impact on marine life depends on factors, such as how the discharge is handled and how the brine mixes with surrounding seawater. Therefore, the question of whether desalination harms marine life is linked to both seawater intake and brine discharge.