Desalination: The San Diego Way…

Proposed desalination plants on the coast of California.

Southern California is being plagued with water shortages. Already an incredibly populous region, population growth is placing more pressure and stress on the region’s water supply. San Diego County in particular (population 3 million), which virtually imports all of its fresh water, faces a tricky natural resource quagmire that leaves all of its residents worrisome about future fresh water supply. With the rising cost of importing water along with the infeasibility of actually meeting water demand (due to increasing population), San Diego has started a massive desalination project. The county figures that taking advantage of its geographic proximity to the ocean would be beneficial for obtaining lots of water- of course it has to be desalinated first.

The project is called the Carlsbad Desalination Project and will be the nation’s biggest plant by 2011. Its purpose is to supply water for the drought-prone county of San Diego. You are probably wondering what the numbers are like: Costs $300 million and is being built by Poseidon Resources Inc. of Stamford, Connecticut. It will produce ~50 million gallons of drinking water each day which is enough to supply 112,000 households in the San Diego County area.

Progress on desalination around the world has hitherto proven to be controversial. Here is my analysis on the Carlsbad Desalination Plant:
Firstly, the plant would be a state driven natural resource management solution and therefore be more locally controlled. This means that once the various water agencies collect the water from the plant, it will be easier to allocate it to the users (residential, commercial, industrial, agricultural). Mainly because water agencies will be closer to the supplier and can help set more rigid standards for allocation purposes which inherently fosters a conservation ethic.

Importing water from upstate can be complicated because water agencies continue to fight over what constitutes “reasonable allocation”. The County currently imports its water at a cost of $526 per acre-foot (1 acre foot equals 1,233,481 litres). Desalinated water would cost $900 per acre foot. A bit more expensive but again, it is more local. Quantity fluctuations and allocation disputes always accompany imported water as reported by water managers in the area.

Importing water also requires an abundance of trucks for transportation. As discovered in the energy usage of bottled water, it takes a lot of energy to move water whether it is bottled or tanked. Smog levels are egregiously bad in the county already, and more carbon emissions in the air would simply exacerbate air quality. Minimizing imported water would help a little bit with climate change stabilization in Southern California.

More on energy: between 60 and 75 gallons of water would be generated per kilo watt-hour, this translates into 4,700 to 5,400 kWh per acre-feet. Water imports from the Colorado River require 2,000 kWh per acre-foot for water delivery and water from the state water project consumes 3,000 kWh per acre-foot to deliver water to Southern California. Therefore, it is more energy intensive to desalinate water but San Diego could be powering its main plant with energy from wind turbines and solar power as an option.

While I believe that water conservation is the most important consideration for any densely populated region, technological projects can provide some relief. A desalination plant in San Diego County, though highly criticized, will set a precedent for other cities to learn from. San Diego has regulations on lawn watering, water metering and water withdrawals that are indispensable for conserving water. Desalination should also face some sort of legislative requirement in terms of how much can be allocated to the users. Moreover, the county should be very strict about how desalinated water is used.

Key message: Water shortages are going to continue to plague the region and if the merits of desalination will help mitigate these shortages, then it is a solution worth pursuing.