Blinded by Science blog #3: How serious of a problem is our supply (or lack thereof) of clean water? I have been hearing about the severe droughts in CA and around the globe. I thought water was a renewable resource so I am confused as to what the real issue is.

Today’s question comes from a reader that has been around since the very beginning (I know this because he liked the Facebook post about my first blog entry, and as we all know, that means he read it).  Ben S. asks, “How serious of a problem is our supply (or lack thereof) of clean water? I have been hearing about the severe droughts in CA and around the globe.  I thought water was a renewable resource so I am confused as to what the real issue is.”

What a topical question.  Hence the quick turnaround from when I received this question to my posting this entry.

First off, let’s begin by highlighting the importance of water.  It’s VERY IMPORTANT!

Now that I’ve gotten that out of the way, we can move on to . . . what?  You would like a little more?  Well okay, but just a little.

Water is absolutely essential to life as we know it.  Not to get into deep and complex examples, but the chemistry that allows life to exist absolutely requires water and its very specific set of physical properties.  In fact, the presence of water on any planet (or moon if it is big enough) is one of the most important factors astronomers look for when searching for extraterrestrial life (which could end up being anything from microscopic bacteria to Wookies . . . or Klingons . . . or Daleks . . . or Xenomorphs . . . or even Sandworms).

Anyway, the human body requires water intake every day and this water has to be safe to drink (lacking disease causing microorganisms and toxic elements).  Water that fulfills this requirement and is therefore safe to drink is called potable water.

Water, water, everywhere,

And all the boards did shrink;

Water, water, everywhere,

Nor any drop to drink.

- Samuel Taylor Coleridge, The Rime of the Ancient Mariner, 1798

As I’m sure you remember from elementary/middle school, water covers around 70% of the Earth’s surface.  That’s an enormous amount of water.  Plus as the question mentions, water in general is a renewable resource (the water cycle).  Unfortunately, the vast majority of the Earth’s water is in the oceans and seas, and as anyone who has been swimming in the ocean knows, the water is very salty.  So salty, in fact, that drinking it actually dehydrates you.  So of all the water present on Earth, the vast majority (close to 98%) is unfit for human consumption or agricultural use based on salt content alone.  That leaves a small supply of water available for human use (be it drinking, irrigation/farming, or industrial use).  This water is accessible via streams, rivers, lakes, or aquifers.  Aquifers are basically layers of rock in which water is found.  Depending on many factors (such as depth, mineral content, salt content, etc.), this water can be used to supply human needs* (plus you do not get the evaporative loss like you do from surface supplies nor are you as likely to have as large an environmental impact from accessing aquifers as you do from building a dam).  In fact, water from aquifers supplies much of the freshwater humans use, including the water used in California.

California is one of the biggest agricultural producers in the world (I’ve seen 5^th largest, but I haven’t been able to verify it) and it produces “nearly half of US-grown fruits, nuts and vegetables.”  All of that farming requires a substantial amount of water, much of which is supplied by aquifers.

Map of aquifers from the US Geological Survey website.

This brings us back to the water cycle.  Aquifers are naturally replenished from precipitation over time, but depending on the depth of the aquifer, this process can take years, or centuries, or even millennia.  So if humans end up using water faster than it can be replenished (especially during drought conditions in which precipitation rates are decreased), you can imagine that we will eventually have a problem.

And that is exactly what is happening in California and other places as well.

Remember how I said that the Earth has an enormous amount of water, but that it is too salty for human use.  Well, we do have the technology to remove the salt and therefore create freshwater for use.  Unfortunately this technology, desalination, is much more expensive than just pumping water from aquifers (it costs around $800 to $1400 per acre-foot of desalinated water produced) and it isn’t able to come close to meeting necessary demand for freshwater.  At least not until the technology improves.

So to summarize the answer to your question Ben:

1)  Water, itself, is a renewable resource of which there is an extremely large supply.

2)  Unfortunately, human uses (including consumption) require freshwater, of which there is a much smaller supply.

3)  Aquifers are a major source of freshwater but if our use exceeds their renewal, they will eventually run dry.  Droughts will exacerbate this problem.

4)  Eventually desalination could alleviate this problem, but until then, we are pretty much at the mercy of Mother Nature.

I hope this answers your question.  If you have need of any clarification or follow-up, leave a message in the comments below.

*Though I didn’t mention it, this water still needs to be purified so that pathogens are removed and it is safe for human consumption.  For a lot of places, access to clean water is a major problem, which is why droughts in those areas can be so devastating.