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As someone who often writes about water, I wish we could come up with some new units of measurement. As it is, we have the gallon, which is too small, and the acre-foot, which is often too big.
The average person knows about the gallon, but since most of us don't live on farms, we have trouble with the acre-foot.
For irrigation, it's a practical unit. If you've got 40 acres, and your alfalfa crop needs three feet of water, then you need 120 acre-feet. It's also a practical unit for storage capacity.
But every time you write about water for a general audience, you've got to explain that an acre-foot is the amount of water it takes to cover one acre. Farmers and ranchers think in acres, but not the rest of us.
So then you need to explain that an acre is 43,560 square feet, which is about the size of a football field, or the floor area of a typical supermarket. An acre-foot is thus 43,560 cubic feet of water, and since there are 7.481 gallons in a cubic foot, there are 325,872 gallons in an acre-foot.
That's not a quantity that's easy to understand, either,
so you crib from some authority. The common explanation
used to be about as much water as a typical household of
four uses in a year,
although with conservation in
effect in much of the state, in recent months I've seen it
go as high as enough water for eight people for a
year.
And that's just one of the common water units. I try to
avoid some of the arcane stuff, like the miner's
inch
(about 9 gallons per minute, though it can vary by
location), but even the usual unit is hard to
visualize.
Flow is commonly expressed in cubic feet per
second,
often abbreviated as cusec
or
cfs.
That's meaningful for diverters and for people
along the river -- I've never seen a cusec, but I know the
Arkansas is roaring whitewater with bad fishing at 6,000
cusecs in mid-June of a wet year, as opposed to a rather
placid stream with good fishing at 450 cusecs in
October.
But it's a unit that has to be explained when you're writing about water for a general audience, and by the time you've finished with the explanation, there's not much space left for what you were really writing about (Black Canyon of the Gunnison reserved flows, Dillon Reservoir capacity, etc.). You start wishing that the new Colorado Water Educational Foundation would do its job so that you could get to the point, rather than explain the terminology.
Thus I propose some new units. The people at Denver Water keep good numbers, and they told me that for planning purposes, they assume that one person in an apartment uses 44,000 gallons a year. We could call this the Annual Personal Water Consumption Unit. It covers cooking and drinking and sanitation, but no exterior use.
Thus our old friend, the acre-foot, is 9 APWCU. My calculations show that a two-person household with 2,500 square feet of lawn and garden used 131,000 gallons in a recent year. That's about three APWCU, and we'll call it a SHAWU -- Small Household Annual Water Unit.
Before we get to figuring reservoir storage capacity in
SHAWUs, we should visualize one. A SHAWU is about 17,500
cubic feet of water, or what it would take to fill a
2,200-square-foot house with 8-foot ceilings. It's about 13
standard railroad tank cars. Assume that an
Olympic-sized swimming pool
is 50 meters long, 75
feet wide, and on average 6 feet deep, and it's a little
over four SHAWUs.
When it's full, Dillon Reservoir holds 632,000 SHAWUs, and the largest reservoir in the state, Blue Mesa just west of Gunnison, holds 2.34 million SHAWUs. Now, isn't that a lot more sensible than 254,000 or 941,000 acre-feet?
As for flow, our kitchen tap just produced four gallons in a minute, but that varies, depending on how many people are watering in our neighborhood. Since the toilet has a tank, its flow rate when flushed is constant -- about 10 seconds for 3.5 gallons.
Our toilet seems pretty typical, but this rate is too
small to be practical. However, we could multiply it by
1,000 to get the kiloflush, and most of us should find it
easier to comprehend a statement like The federal and
state governments have agreed to a minimum reserved flow of
6.4 kiloflushes through Black Canyon of the Gunnison
National Park
as opposed to 300 cfs.
Now, if I can just persuade everyone else to start using kiloflushes, SHAWUs and APWCUs, we could actually start writing about water issues, instead of devoting most of every article to explaining acre-feet and cusecs,
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