To Understand Water, Learn the Math

Originally Published on March28, 2014 | National Geographic – Water Currents |

OK, I’ll admit to being a bit of a geek when it comes to water numbers.

I never got all that excited about algebra in school, and college calculus was a real struggle.  But water numbers fascinate me.  If you’ve read any of my earlier blogs it will be apparent that this fascination borders on obsession.

Don’t get me wrong.  I can be perfectly content sitting on the bank of a river and watching the water flow by, never thinking about the number of gallons moving downstream.

But I find that numbers can be really helpful in understanding the causes of water shortages, or how much water we are wasting, or how often you might expect a flood of a certain size.  When you gain a quantitative grasp on the volume of water falling on the land as rain or snow, the volume moving into rivers or aquifers, or the amount of water being used in cities, industries, or farms, a much fuller water picture reveals itself.

That’s why I got excited when the Electric Power Research Institute (EPRI) recently released its new report on “Evaluating Thermoelectric, Agricultural, and Municipal Water Consumption in a National Water Resources Framework.”

Bear with me.  I’ll explain why this report is important.

To really understand what is happening with the water in a particular river, lake, or aquifer, or even at the scale of an entire state or country, you need to build a “water budget” – an accounting for how much water is being supplied by rain or snow, how much is being removed from each water source, AND how much gets returned to the water source after use.  The volume that is removed and NOT returned is called “consumptive use” or simply “consumption,” as illustrated in the diagram below.  If you want to understand why or the rate at which a river, lake, or aquifer is being depleted (dried up), you absolutely need to know how much water is being consumptively used.

To truly understand what is happening with the water in a river or aquifer, you need to keep track of how much water is being replenished, withdrawn, used, and returned to the original water source after use. The portion that is “consumptively used” causes depletion of the water source. Illustration from Chasing Water: Moving from Scarcity to Sustainability (Brian Richter, Island Press, 2014)

Read The full Article at Nat Geo