How could wells back in the day work? [closed]

Question

One of the many things that have confused me all my life is the concept of wells.

I get that somebody, long ago, discovered that there's sometimes/often water in the ground, once you dig deeply enough. And they therefore started digging wells and putting rocks around the cylinder-shaped hole in the ground, supposedly to stabilize it and perhaps prevent the water from becoming too dirty.

1. Wouldn't the water automatically become dirty rather than clean, from the dirt in the bottom of the well? (And if the bottom is not dirt, how did any water get into the well in the first place?)
2. Couldn't any person who didn't like the person living in the house just walk up to the well when they are asleep or away and drop something disgusting down there, ruining the well completely? I assume that this was one of the reasons that wells evolved into pumps, which have no obvious way to contaminate them (easily)?
3. If wells automatically work from the ground just "doing its thing", how can there be such a thing as a "dried-up well", abandoned because it no longer gives water?

I have tried reading the Wikipedia article, but as usual, the illustrations and descriptions mostly serve to confuse me further.

Answer 1

1. The bottom of the well is not "dirt" but some kind of soil, or sand, or gravel. Have you ever seen a clear stream? From which you can drink? Same with the well. A stream is a place where underground water surfaces. What could dissolve in the soil, already dissolved long ago. What remains are mineral particles which do not muddle the water unless you disturb them.

2. This is a strange question. Usually there is one or two wells in a village. I mean most wells are not private but community property. If you contaminate them where will to take water from for yourself? You will harm not only a particular neighbor you hate, but the whole community. There are many other ways to do harm to your neighbor. To burn his house, for example, or to put a bomb or a poisonous snake in his mailbox. Such things happen, of course, but not frequently, in a civilized society. Actually wells have been contaminated on purpose, during some especially severe wars, this is a part of "scorched earth" policy. Also burning the crop in the fields and cutting fruit trees. Such things are also done sometimes by criminals. Communities usually deal with these criminals in the most harsh ways.

3. The level of underground water can change for many reasons, geological, climatic etc. When it goes down, the well dries up.

Remark. Once I walked for few days in the Negev desert (now in Israel), and I used a well which was at least 2000 years old (known in the Nabatean period. It had a name.) The maker of the map that I used was not sure whether there is water in it or not. It was marked as an "ancient Roman oasis". Since this was the only possible source of water on my way, I carried bottled water for 4 days. When I reached the well, it was in perfect shape, functioning, and the water was tasty. I discarded some water I carried, to decrease my load:-)

Answer 2

I doubt these answers are worth any valuable StackExchange points, but...

1) Probably, yes, there was some silt in the water. But the water at the bottom of the well would be pretty still, allowing the dirt to settle to the bottom.

2) I'm sure that well sabotage has happened at some point in history, but, social norms and hideous medieval punishments aside, in a village you'd just be poisoning yourself too. In a rural setting of stout hard-working yeomen, I doubt that'd be any more common that pouring sugar into your neighbor's gas tank would be, these days. I'm sure that wells also evolved into pumps because it'd be a lot easier for a machine to drill a smaller hole than for people to dig out a 3-foot-diameter hole.

3) Underwater streams can dry up, and, long-term aquifiers can dry up.