Benefits of a Rain Garden

The whole reason I'm installing my vernal pool, or rain garden, or whatever it is, is to restore a little bit of natural ecology as well as reduce the amount of urban runoff into our storm drain systems.

"But, John," you protest, "how much runoff are you really eliminating with your little 110 square foot pond?"

Glad you asked. Hey, math time again!

110 square foot pool surface area
* 1 foot average pool depth
__________
110 cubic foot pool volume
* 7.48 gallons / cu. ft.
__________
822.8 gallon capacity
* 66% full
__________
543 gallons

That's right, in Friday's storm my little pond held well over 500 gallons of rainwater — not counting what it percolated during the storm — and ultimately released it back to the earth rather than letting it flow out to the gutters or dumping it out at my home's foundation, whether into a French drain or not.

543 gallons and counting? I'm feeling pretty good about myself right now.