Achieving Water Security by Becoming Water Self-sufficient

by on September 19, 2009 · 7 comments

in Environment, San Diego


Water, water everywhere and all we want to drink, shower in, swim in, grow food with, etc.

by Jim Bell

Many experts are projecting doom and gloom, scenarios of decreasing water supplies and increasing cost, yet the San Diego/Tijuana Region can easily become renewable water self-sufficient and even become a net water exporter.

Even if we assume the worst case scenario of zero precipitation and the complete cutoff of all imported water, the San Diego/Tijuana Region could completely replace all the freshwater it currently uses by installing PV panels over 4.3% of its roofs and parking lots. In 2015, 4.3% of our region’s roofs and parking lots will be about 9 sq. miles, or 4.5 sq. miles on each side of the border.

The above statement is based on the following assumptions:

1. A yearly average of 5-hr. of sunlight per day,

2. 1,000 sq. feet of roof and parking lot per capita,

3. An average potable water consumption level of 180 gallons per capita per day,

4. A 2015 regional population of 6 million people,

5. That 70 gallons of freshwater can be extracted from seawater per kWh of electricity consumed through reverse osmosis (RO)

6. PV (photovoltaic) panels 15% efficient at converting sunlight into electricity, (Commercially available panels are already pushing efficiencies of 20% or better.

The electricity produced by this system would be used to power large scale reverse osmosis (RO) pumps to convert seawater into freshwater. The pumps push seawater through filters that let freshwater through while excluding salt, other minerals and contaminants in general.

The issue of sucking marine life into reverse osmosis system can be solved if seawater to be processed into freshwater is extracted from wells close to the ocean above high tide instead of direct ocean extraction. Since seawater coming into such wells would be sand filtered, marine organisms will be eliminated from the process.

Similarly, since “waste water” from the RO process will be twice as salty as seawater, it will have to be diluted by mixing it with seawater, also extracted from the near ocean wells, until the water to be returned to the ocean is no more than 20% saltier than seawater. Once diluted, its release into the ocean would be defused as an additional precaution against negative ecological consequences. Other sand filtering technologies have also been proposed.

Mining RO waste water for salt and other minerals opens up other local business and employment opportunities for the region and could potentially eliminate the need to return RO wastewater to the ocean at all.

The size of the “worst case scenario” RO system discussed above could be cut in half, if recycled sewage water was filtered and disinfected, then used for irrigation. Using graywater at home would also be a plus for efficient water use. This is because half of the potable water currently used in our region is used for irrigating landscaping and crops.

Water-use efficiency improvements could reduce the role of renewable-energy-powered RO as well.

Combining water recycling and efficient water use with better rainwater runoff collection and storage systems, our region would only need to install 15% efficient PV panels on 2% of its roofs and parking lots to provide equal or superior water use services in the future, compared with what we have today. Plus, if we want more freshwater, we can cover more roofs and parking lots with PV panels to power expanded RO capacity and create all the freshwater we want.

Additionally, all this can be funded through a water purchase agreement model that will pay for itself by redirecting the dollars we now export to pay for imported water into hiring local businesses and workers to make our region renewable water self-sufficient, with renewable energy powered RO being our back-up for water if all else fails.

{ 7 comments… read them below or add one }

avatar nunya September 19, 2009 at 11:59 am

Crops? Who can afford to grow crops here anymore? Why hasn’t Ahhhrnold offered tax breaks for greywater systems?


avatar nunya September 19, 2009 at 12:04 pm

Ooops, my bad, reading AB 1420 now.


avatar BillRayDrums September 19, 2009 at 5:14 pm

The surface area of the planet required to power the entire world as we know it, using merely solar panels.


avatar Larry OB September 19, 2009 at 7:57 pm

A couple of months ago, one of the orange aprons at Home Depot tried to sell me a rain gutter install while I was selecting some lumber. I asked him if they had a comprehensive program to do gutters, barrells, and cisterns. He made a face, and said, “no, barrells attract too many bugs…we don’t do barrels at Home Depot.” I told him, “too bad, because then you could be a leader in the industry instead of just a follower.”

I know it’s a DIY project, but are there any local contractors filling that niche? A combined gutter and storage installer?


avatar Larry OB September 19, 2009 at 8:06 pm

A lot of water goes into the plants, but how many are edible plants? Any good estimates on that? I think we sh0uld be able to water our edible plants and trees any day of the week.

Jim, how about solar panels along the North side of the OB Freeway? Would that be enough electricity for the Peninsula? Good place for the wells, too? And them noisy pumps.


avatar BillRayDrums September 19, 2009 at 8:19 pm

Sorry, I should have prefaced my comment with “another form of sustainable energy is:…..”



avatar Shawn Conrad September 20, 2009 at 5:51 pm

Relax everyone, we have 75% water + the polar ice caps that have yet to become water.

In the mean time, here is a water saving tip!:

1) Engage your hazard lights and pull over to where the city has a sprinkler geysering into the shoulder of the road to wash your car.



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