An interesting topic given that just yesterday morning I was out taking those very measurements after a pretty heavy rain Friday night here in NW Ohio.

Firelshot, the short answer, like others have said, is impossible for anyone to answer, but yourself. With a good quality rain gauge and a constant benchmark location for measuring your pond level you can collect the data needed to come up with a baseline from which you will be able to forecast the impact on your pond with reasonable accuracy. I have been monitoring mine for about six months.

A little background on my pond. It is approximately 1/10th of an acre. 50% of the pond is 12' deep at optimal water level with 50% sloping up to about 4' of wading area then up again to a beach area. The bank is cut at two different angles. From the high-water line up to the natural ground but below the overflow the sides are cut to 3’-1 slope. Just below the optimal waterline down to the bottom the sides are closer to 2'-1'. Fully clay lined up to and beyond the topsoil line, no springs and no natural water tributaries. It is supported 100% by run-off only.

Here is where I have taken normal run-off physics into my own hands in that I have plumbed 100% of my 2800 sq.ft. steel roof drainage into the pond as well as two sump pumps under my house. All this leads to power filling capabilities in my small pond.

Over a 6 month period of time I have been able to come up with an average figure that shows for every 0.50" of rain that falls on my property I will see a 2-7/8”-3" rise in my pond within 12 hours of the end of the rain. As others have said there are variables that can impact this like rain intensity, dry or wet area ground conditions at the time of the rain, wind duration and so on but by getting a large enough cross section of measurements over time you can factor those variables out through averaging. Again it’s not an exact science but pretty close.

Directing so much drainage into the pond has allowed me to maintain fairly consistent water levels throughout this year’s drought while many others in my area were left looking out at mud where water once stood. The downside of course is the potential for a rapid and intense over-flow so you have to plan for that and be sure of any impact you might have "downstream" from your property. Also I don’t want to turn my pond water over too quickly. I prevent this by having my drainage pipes positioned such that if the water rises to my high-water line it covers the exhaust end of my pipes creating head pressure resistance sufficient enough to trigger by pass outlets. The drainage water will simply take the path of less resistance and re-direct it’s self into alternate pipes “up-stream” that are directed away from the pond into a grass waterway at the back and sides of my property.

Last edited by Waterbug; 09/09/12 03:31 PM.