Crap Detecting 101-1: Are 70M Gallons & 50M Square Feet Large Numbers? Not Necessarily in California!

Crap Detecting and California Water
In my classes I try to teach my students to be 'crap detectors'. I could have used 'critical thinkers' but the former term is more endearing to me: it's from the title of an address given by Neil Postman in 1969, "Bullshit and the Art of Crap-Detection". It struck my fancy as an undergraduate looking for out-of-the-box thinking. 

In the water world we often focus on volumes of water. It can be hard to decide which units to use. You want to make the numbers understandable to your audience. I am inclined to use acre-feet for large quantities; one acre-foot is about 326,000 US gallons. So how much is that? It's about half an Olympic-sized swimming pool or a football field with about 10 inches of water on it. The latter usually works, at least in the USA.

But at times the choice of units is more duplicitous. One of the most popular ways to spew crap vis-a-vis water volumes is to use units that help to make a point or advance an agenda. This is effective because there are so many different volume units, from very small to very large. And, if one is dealing with flow rates - volume per unit time - additional options can be employed - the time period (seconds, days, months, years...). The geographic scale is important - are you talking about statewide water use, local, household, or some other scale? Are you comparing your number with another one?

The current California drought provides a plethora of examples regarding freshwater use.  I am not suggesting that the examples are duplicitous. Consider the following.

How much freshwater does California withdraw (I am equating 'use' and 'withdrawal'). In 2010 the figure was about 31 billion gallons per day or 11.3 trillion gallons per year. I got this number from the bar graph in this USGS brief, and assumed thermoelectric water withdrawals in California are not freshwater (see page 1, second paragraph, of the aforementioned brief). Here goes.

1) Fracking Amounts
A few days ago an article was making the rounds on Twitter about how California had used 70 million gallons of water for fracking in 2014. Many people who retweeted the link were indignant that this much water was being used in a drought-stricken state. [Click here and scroll down to see some of these Tweets.] If you read the article, you knew that amount was puny - about 215 acre-feet per year or the amount of water used by about 512 households. Why puny?  Fracking accounts for 0.00062% (or 0.0000062) of the state's annual freshwater withdrawals. A lot of water? Not in my book. In fact, I thought there was an error - that the figure should have been 70M gallons per day. But note that locally 70 MGY could be a significant amount.  

Note that even if the number were 70 MGD, that would be about 25.6 billion gallons per year or 0.2% of California's annual water use. That's starting to make a dent, albeit slight.

By the way, I don't fault the news source (Reuters) for using '70 Million Gallons' in the headline. How many would have read the article had it trumpeted ''215 Acre-Feet Used in Fracking'?

LA Times columnist Michael Hiltzik put it another way: the amount of water used for fracking equals about three minutes' worth of California's annual water use. 

For another claim about fracking water use in California, go here.

2) Nestlé's Bottled Water Use in California
At this site (source of the graphic) I learned that Nestlé's bottled water operation uses 400 million gallons per year. Whether that's accurate or not I don't know. But for my purposes, it does not much matter. Many people no doubt groaned when they saw that number - even more indignation than expressed at the fracking number. Again, 400 MGY (about 1225 acre-feet per year) is a huge number, but statewide that is 0.000035 or 0.0035% of California's total. That's about 17 minutes' worth of California's annual water use. But the water use number could be significant locally. 

3) 50 Millon Square Feet of Grass
I owe this item to Tom Swihart's Watery Foundation blog,. He noted that Governor Jerry Brown's recent executive action called for replacing 50 million square feet of lawn with drought-tolerant landscaping. Wow! That's a lot of lawn! Fifty million square feet is about 1.8 square miles. How much lawn does California have? Somewhere between 3,300 and 4,300 square miles of lawn, including golf courses. Let's take 3,800 square miles. So 50M square feet is about 0.0005 or 0.05% of the total. Is that going to make a dent in the drought? Hardly. As Tom noted, 50 billion square feet would have been more appropriate. As one wag noted, Governor Brown's legacy could be that he replaced 50M square feet of thirsty grass! And no, not that grass!

4) 13 Trillion Gallons of Water in the Colorado River Basin
When Jay Famiglietti and his colleagues broke the story about the loss of water from the Colorado River basin over nine years they spoke of groundwater loss in terms of cubic kilometers (50.1) or million acre-feet (40.5).  Not big numbers, right?  How about in gallons? One CBS reporter used the figure 13 trillion gallons - correct, and of course, more relevant to the person on the street. How many know people how big a cubic kilometer is (810,000 acre-feet) or an acre-foot (326,000 gallons) is? The reporter made the amount relevant. Actually, the press release did a great job, describing the loss in terms of about two Lake Meads.

Upshot
Choose your units carefully, and be cognizant of the fact that the units you choose may be 'loaded' and subject to misinterpretation. Think of the spatial scale.

And remember Postman's Third Law:

“At any given time, the chief source of bullshit with which you have to contend is yourself.” - Postman's Third Law 

Comments

[Thomas Meixner]

Nice dodge in the graphic you show as well. Assuming California has 40,000,000 people (rounding up from 38,000,000) and folks use the bathroom 5 times a day (rough guess) those toilets are using ~120,000,000,000 gallons per year (120 billion gallons) or about 350,000 acre feet convert all to 1.2 and make the men use waterless urinals and you save probably half of that.

Thanks, TOm

PS Crap detection works particularly well for discussin the water usage of toilets.

[Account Deleted]

ps/Michael -- SI would make it TOO EASY to see what's going on...
http://www.aguanomics.com/2015/03/how-much-do-you-pay-for-water-you-use.html

[Account Deleted]

Awesome examples!

[Michael]

What is wrong with SI units?
http://en.wikipedia.org/wiki/International_System_of_Units