You mention you have various water buts dotted about to catch water from roofs etc. Even a small shed roof or greenhouse roof will fill a water butt in no time.
One of our more ingenious plot holders has three 100 litre plastic storage tanks which have all been filled from a single greenhouse roof. The rainwater is fed to a water butt, each time it gets somewhere near full he has a hand pump, very easy to use just move the lever backwards and forwards with one end of a hosepipe into the water butt, the handpump fastened to the wall above butt and a pipe leading to whichever container he is filling at the time
I myself have a 1000 litre container which was filled very quickly from my 8X12 greenhouse roof.

I don't particularily like digging so I mulch!!! Apart from it conserving moisture I let the worms do the digging for me as well.
Any organic matter will do, cardboard,paper, straw,manure,grasscuttings,compost,woodchips etc

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My Majesty made for him a garden anew in order
to present to him vegetables and all beautiful flowers.- Offerings of Thutmose III to Amon-Ra (1500 BCE)