Thursday, September 27, 2007

Even A Litle Rain Is Valuable

To see just how important every hundredth of rainfall is, let's quantify it in terms of gallons.

1 inch of rain falling uniformly over 1 acre of land is approximately 27,154 gallons of water.

Here is one more calculation -- there are 640 acres in 1 square mile.

So take Denver for example. There are 153.4 square miles in the city. Multiply that by 640 acres per square mile and you will see that Denver has 98,176 acres.

SO if the city were to receive 1 inch of rain over the entire real estate -- we would multiply 98,176 acres * 27,154 gallons per acre to see that 2,665,871,104 gallons of water fell from the sky. That is over 2 BILLON GALLONS!!

Now there are many other factors obviously to consider. For us here in a dry climate, there is evaporation. For any urban area there is runoff. So not all those gallons necessarily make it into the ground water and surface water, but as you can see, precipitation is the lifeblood of our lives!!

So now you see that even a few hundredths falling over an entire city is extremely important. So the next time you check your raingauge and see just a measily 0.01 or 0.04 -- don't be too let down, go back inside and convert that to gallons.

Then look at your local maps and see the coverage of the rain.

When you think of rain (or melted snow) in terms of gallons, you not only see how important you are as a volunteer weather observer helping us to see what is happening out there in between all the official weather observing points, but you also quickly see that every single drop counts -- LITERALLY!

To convert snowfall -- the standard equivalent is 1 inch of rain to 10 inches of snow -- so for 1 inch of new snowfall, you would run the calculation as stated above and then divide it by 10.

However, that snow to water ratio isn't true for everyone. Here in the Rockies in the dead of winter, we can see snow-water ratios approach 30 inches of snow to 1 inch of water -- thanks to that dry Rocky Mountain powder.

I will be traveling until Monday night so blogging will be tough for me to do -- but if I get a chance, I will.

Have a great weekend everyone!


  1. We live on 10 acres and my rule of thumb is: a hundredth inch of rain equals 50 gallons. Doesn't sound like much until the multiples kick in!

  2. WOW - never thought of it like that!! Thanks!!