Ah yes, details probably help. Forgive the rookie and let me know if need more.
I probably mis-described as "rainwater" harvesting. The cistern draws from my gutters for sure, but the main supply is better described as the "well under my basement" - the naturally high water table that keeps my sump-pump capable of running pretty-much all year (i have a "high" and a "low" pump, I usually turn the "low" pump off after spring or it really would run all summer and try to pump out the lake under my home).
Anyway, enough I think to charge the cistern so that it can keep-up with the effort.