Mad thought it was a septic tank???
They were usually used to collect rain water off the roof gutters, for places that had low output wells like the place I had. But no way in hell was I going to use that cistern.
There were two dug wells on my property, the one the house was hooked to would usually run dry in the fall. Gigantic PITA. A water guy would come and fill it, but constantly conserving water, not knowing when/if it would run out, sucked ass. They are usually fed by surface water that drains down through the soil.
I had one drilled and he hit salt water, which he mentioned beforehand was a possibility. So I paid him, put a flat rock over the casing, some dirt and seeded it. I hooked up to the other dug well which had plenty of water.
Dug wells are a PITA, which I had here until 2005, but had plenty of water. And they are not sanitary.
The well I had drilled here hit plenty of water but it is loaded with iron. Had to have a special $2,500 water softener put in to deal with it, which it does very well.