Lets talk about water catchment tonight....I just received delivery of three 3000 gallons storage tanks. Had them dropped at the end of my driveway for now as I have to prepare the pads (leveled sand) for them on the east end of the greenhouse.
To begin with, we will use the following formula: 1" of rain per square foot of surface area = .6 gallons of water. My little patch of Texas averages about 9" of rain per year (mostly in Aug, Sept, and Oct) My total storage capacity is now at 21,650 gallons - the new 9000 gallons of which will be guttered in to the roof system on the greenhouse. I will need 7.5" of rain per year to fill these tanks off a 2000 sq, ft. roof.
My little hut has a 550 gallon tank guttered in. It has only overflowed twice in two years from the runoff of the small roof on the house. Next to the seasonal draws on my property I have 12,100 gallons of storage capacity. Last good rainfall that I caught - I was able to pump 3000 gallons in just under an hour into one of the tanks. Over the past year I have collected and stored about 9000 gallons from this runoff to be used for greenhouse irrigation later this year. The beauty behind these seasonal streams is that water runs through them from an area about a quarter mile square. Not accounting for what soaks into the ground - that much area equals 4,181,760 gallons of water rushing by my place after only 1" of rain. It's all a matter of being ready to catch it and having a place to put it when it happens. 54,80,32,0