Finally made some progress in capturing and storing rainwater. The north half of the barn roof now flows in to a 350 gal. ( 1325 l) tank, and I have installed a gravity driven drip system to our fruit and nut trees downhill of the barn.
The routing might look goofy, but I was trying to place supports that tied in to the internal structural, find a level spot, keep the tank on the north side where sunlight ( causes algae) is minimized, as well as not being below the window.
This is still not enough capture, so I plan to expand the storage to catch even more of the rainwater. Plans for the south roof flow are to irrigate the south garden. When I get that side finished I'll post an update with photos as well.
Barn is 30 ft. ( 9m) x 60 ft. (18m), so a 1 inch (25mm) rainfall will provide 150 cubic feet, ( 4.25 m3) or 1100 gallons (4200 l)
Since each downspout is catching half the roof, this setup could potentially get 550 gallons (2100 l) from each inch of rain.
Average annual rainfall for here is 36.56 in. ( 928mm), which is a generous amount of rain, so I really just want to save enough to get through drought stretches as long as this setup is just for trees and supplementing rain in the veg gardens.
If we decide to try to rely on rain for more uses, and the well pump for less, then the need is a great deal larger. For now, I plan to increase storage enough to capture rain from April through August, which is about 17.6 in ( 450mm). That's a lot, but I would stay with above ground storage, and simply drain and shut down in the winter.
If we try for year round use and storage, then insulation or an in gound cistern will be needed.
The drip system has had some problems to consider. First, it was hard to find components that are suitable for low pressure . Many catalogues have "low pressure" fittings, but this means 5-15 psi ( 35 kPa- 105 kPa). Since I am using only gravity, I have much less than than, somewhere in the order of 5-15 feet of head. I found some that are marginal, but the flow is still not very good.
Second, running it above ground means that once grass and weeds grow up, it is hard to find! I put out a few flags, but need to do some more to make sure we don't damage it and can find it if maintenance is needed.
Third- It will be hard to drain all the way before freezing temps arrive, without taking it all up and coiling it. I may try to blow it out with air.
I got this finished late in the season, but it should really give the trees a boost next year.