Feb 112018

Cape Town rejoices as rain falls on drought-striken city

When it finally came, restaurant diners rushed outside mid-meal to see the deluge for themselves.

A Deluge? Sounds like good news, yes?

South Africa’s second-largest city and its surrounding areas received between 2 millimeters and 10 millimeters of rainfall Friday night, according to the Cape Town Weather Office.

Ummm… averaging less than 1 centimeter is a “deluge?”

The city can expect 2 millimeters to 8 millimeters of rainfall Monday evening and into Tuesday morning — less than an inch

Holy crap! Eight millimeters is less than an inch! My whole world view has been turned upside-down! Thanks, CNN!

Later after claiming this slight drizzle to be a “deluge” the article finally mentions that it will have approximately zero impact on the actual dire water situation.

Come Day Zero, just a few short months from now, pretty much all the taps in Cape Town will be shut off. This is of course a nightmare for the city. But once again, though, Cape Town sits right on the ocean. And while the big desalination plant is still years from completion, I gotta wonder: if even a quarter of the population built themselves some solar stills, could that make a difference? From the wiki on solar stills:

In 1952 the United States military developed a portable solar still for pilots stranded on the ocean, which comprises an inflatable 24-inch plastic ball that floats on the ocean, with a flexible tube coming out the side. A separate plastic bag hangs from attachment points on the outer bag. Seawater is poured into the inner bag from an opening in the ball’s neck. Fresh water is taken out by the pilot using the side tube that leads to bottom of the inflatable ball. It was stated in magazine articles that on a good day 2.5 US quarts (2.4 l) of fresh water could be produced. On an overcast day, 1.5 US quarts (1.4 l) was produced.

2.4 liters per day is not a spectacular amount, but that’s 2.4 liters per day from a single portable solar still 24 inches in diameter. A rooftop 20 feet by 30 feet could support at least 150 of these stills, producing a theoretical 360 liters per day. In order for this to work, there would of course have to be ready access to sea water; easy enough if you’re on the beach, much less so if you’re up hill. But at this pint it seems like it would be easy enough to build some Big Ass Pumps to shove a couple hundred tons of seawater uphill every day to collection points where solar stills could turn it into a combination of fresh water and highly saline brine.

A quick check online finds the “Aquamate” inflatable solar still that sounds a whole lot like the military one from the 50’s. At $270+ each, it’s insanely expensive for this purpose, but since it seems like a  simple enough device, you’d think that an order of One Point Two Bajillion of them would serve to drop the per-unit price down to… well, not much. It’s just some plastic after all, seemingly not much more complex than a beach ball or a poncho.

I’m not picking on Cape Town here. It’s just that that town is currently in the news about a dire humanitarian crisis that seems like it can be solved, or at least greatly lessened, with the application of some STEM. And where Cape Town is now, other places will be sooner or later. If Cape Town can get it together and use science and engineering and sheer force of will to smack mother nature around and show her who’s boss, then that’ll be a sign that humans can conquer nature all over.

 Posted by at 3:29 pm
  • Wouter de Waal

    It’s not as bad as they make it out to be.

    But they have to make it out to be bad, otherwise people won’t save water. And then it will be as bad as they make it out to be.

    Because people are stupid.