I addressed this topic three years ago, when Southern California was in the middle of our terrible drought that has since been at least somewhat alleviated, depending on where you live.

Since then our country’s largest Desalination plant has opened in San Diego, and it supplies around 300,000 area residents with their fresh water needs. Just a few months ago nearby Santa Barbara reactivated a desalination facility that operated for a time in the early 1990s during an earlier drought but was mothballed when the rains started coming again. (It remains to be seen if history will repeat itself.)

Some further reading about the subject informed me that desalination is actually more common than I thought, both in our country and around the world. Several Years Ago Bloomberg News reported that more than 300 municipal desalination plants were operating in the U.S., most of them in Florida, with another 45 (as of 2013) in California, the second most abundant state. Additionally, various industrial desalination plants are in operation serving individual factories.

Most of these are small-scale operations aimed at providing fresh water supplies to isolated communities near convenient salt water sources. Desalination is generally thought of as a last resort for obtaining fresh water, because it is energy-intensive and expensive. More than half the operating costs of desalination plants are devoted to providing the electricity needed to run the process, and the electricity usually is generated via fossil fuels. So while desalination helps solve one environmental problem – water shortage – it adds to another. As a result, most environmentalists take a dim view of desalination.

And that brings me to another reason why this subject popped up again. An obvious solution is to use renewable energy to generate electricity for desalination, but that’s easier said than done owing to the large amount of energy required.

Now comes some promising research at Rice University that has tweaked solar technology to the point that it becomes viable, at least for small off-grid locales. Continuing research may enable the technology to be scaled up. That would be great news for Southern California and every other part of the world where fresh water is in short supply.

At some point in our school years, most of us learned about what’s known as the hydrologic cycle. It starts with water being evaporated from the oceans, then falling as precipitation, where the water accumulates in the ground until brought to the surface via wells or running off as rivers and streams back into the ocean, where the process begins anew.

A key point of the hydrologic cycle is that the total amount of water available on earth hardly ever changes. Some molecules drift away into outer space but not enough to make an appreciable difference. Our planet has an abundance of water, but only around 2.5% of it is potable.

So when we speak of a water shortage anywhere on earth, we are really referring to the uneven distribution of drinkable water. Since the vast majority of water is taken up by the oceans, it makes sense to look at desalination as a long-term solution to fresh water shortages. That won’t happen in a big way until we eliminate the environmental downsides of the technology.

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