Proposed City of La Paz Desalination Plant
Chris Salter, February 2011

Following a virtual four-year drought, there is a potable water crisis in La Paz and the desalination of ocean water appears to be the only logical solution to cost-effectively address this problem.  The newly elected State Governor and City Mayor have both pledged to prioritize the construction of a desalination plant to convert ocean water into potable water. 

The production of more bottled water is not a solution because its production involves the wastage of about 40 per cent of the fast dwindling municipal supplies.  Furthermore, this waste water is loaded with sodium and other concentrated mineral salts and it isn't even suitable for irrigation.

Most professional water treatment consultants would have no problem with the construction of 10,000 desalination plants around the world, each with a daily production of 10 million gallons to provide the equivalent of 16 gallons of quality water, each day, for every single one of the world's 6 billion inhabitants. Returning the resulting concentrated reject brine back into the ocean is not really an issue because we are only putting back that which we borrowed in the first place and it would quickly be diluted in our vast oceans. In 10,000 years' time the daily return of more than 12 billion gallons of concentrated brine from these 10,000 desalination plants would only increase the average ocean salinity by less than one half of one percent.

However, to build a single, 10 million gallon per day, desalination plant on the shores of the Bay of La Paz, the "jewel-in-the-crown" of the state capital city, would be one desalination plant too many. The relatively shallow waters and slow moving currents of the bay would, over time, create major dilution problems for this vitally important ecological preserve.  Jacques Cousteau would turn-over-in-his-grave at the mere thought of this impending catastrophe.

The City of La Paz requires 16 inches of rainfall every year to replenish its underground aquifers, but over the past four years La Paz has only received an accumulated rainfall of less than 13 inches.   We desperately need a desalination plant but having ruled out the Bay of La Paz, where can we put it? 

Fortunately, there's a narrow land mass just north of the City that reaches out to Isla Espiritu Santo and separates the Bay of La Paz from the Sea of Cortez.  On the Sea of Cortez side of this peninsula the much deeper Sea, with its fast moving currents, provides a logical dilution stream for the reject brine with minimum ecological effect and damage.  This coastline is sandy, which provides the ideal vehicle for the construction of beach-wells where the desalination plant feed water has already been subjected to a natural filtration through the sand underneath the sea water minimizing the intake and subsequent destruction of any aquatic life.

Conversely, to construct a 10 million gallon per day desalination plant on the Bay of La Paz would require the direct intake of the water from the Bay which has two algae-blooms and two red-tides (highly toxic algae-blooms) every year. 

This will require extremely expensive pre-treatment and probable extensive desalination plant shut-downs, both of which will significantly increase the cost of the delivered water as since fixed daily costs of finance, management, staffing, etc. still have to be factored into the price of the water.

Hopefully, the newly elected powers-that-be and their advisors will do their homework, especially the mathematics of the trade-off between the capital and running cost vs. the ecological concerns.  Having done this, they will quickly realize that the construction of a beach well fed desalination plant on the shores of the Sea of Cortez, even taking into consideration the cost of building and pumping water through a delivery pipeline to the municipal treatment, blending and distribution ponds, will be highly cost-effective.

There are a number of major developers that currently own many square miles of property adjoining this coastline who would be be happy to donate the required land and to finance, with the contribution of some Federal Government funds, the cost of the desalination plant, beach-wells, supporting infrastructure and delivery pipeline.  In addition, they will manage the plant and sell the water to the City at a competitive price.

To achieve this, they would have to partner with an acknowledged major "brand name" desalination plant manufacturer who has extensive knowledge of the waters surrounding Mexico and who has access to all of the latest "state-of-the-art" technologies to ensure that both the capital cost and running cost of the desalination plant will deliver the water at the lowest possible price.

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