I apologize if this is not clear and pretty long, but it's my first time on the site, and I do medicine, not engineering)
I am part of a community garden club at my medical school aimed at providing healthy (& usually store-expensive) vegetable options to underserved persons in our community. We recently expanded in the last year from 3 4x8 raised garden beds to 6 4x8 and this year added 4 5x10 raised beds. Last year, we built a gravity-fed, "zero-pressure" drip system for the 6 4x8 beds, which was mostly successful, other than not having enough of a reservoir (1, 77-gal barrel on a 3' platform with an automatic timer fed by a gutter of 150 sqft roof), but with the expansion, we are not sure how to sustain the autonomy of the system. We recently obtained a 330gal rectangular tank for the main reservoir, but have yet to elevate it (space is limited, and we only have the one gutter to tap). In addition to the space and water-source problem, we anticipate having pressure issues (needed to supplement irrigation with manual watering many times in dryer months) again, and are not sure how to fix them, as the roof from which we get the water is only 7', and we cannot reasonably raise the tanks much higher and still have them fill. Yet another issue with the idea of using a pump to supplement the pressure is that we have no access to any power outlets.
My original idea was to attach a 55gal barrel side-by-side with the 77gal (increased capacity at the raised height), then run an overflow pipe from the top of the 77gal into the 330gal tank to capture as much as possible during this rainier time of the year (we are in northeast PA, and last July we did not have enough water to maintain the system), but the issue then arises with how to send the water back up to the raised barrels to supply the beds. I toyed-around with the idea of purchasing a 2m lift solar fountain pump that would continuously pump the water from the large 330gal reservoir into the barrels, and just let the overflow drain back into the reservoir via overflow pipe, since solar power won't be wasting any energy and it would ensure the barrels stayed filled to maintain more pressure. This makes logical sense to me, and is practically simple, but I do not know enough about low pressure irrigation systems to know if this would work out in actuality.
A little basic/general background on the plot:
The 6 4x8 raised beds are closest to the barrel (furthest 2 are about 25-30' away)
The 4 new 5x10 beds are about 10' to the right of the barrel and another 10' in front (see attached picture of the excel layout we made)
I know we need 392sqft x 0.623gal/sqft/wk (including natural rain) to supply them adequately
This is long-winded and probably not too clear, but I have attached a picture of our layout that will hopefully help it make a little sense. My actual question is: how can I rig up a system that will supply all of the beds that is fully or almost completely automated, particularly with the pump, as pressure became an increasingly annoying issue last growing season. Please ask any questions you may have, and try to keep in mind that children will be playing and gardening here, so no open wires or dangerous things. Also, we are future doctors, not engineers, so while we are pretty good at improvising and making things work, we will never be engineers or electricians, so we are trying to devise the simplest system possible that maintains its functionality.
Thank you, and any advice/plans are greatly appreciated!