A friend of ours out in the Texas Hill Country uses a underground spring for their water. A windmill pumps the water up to a limestone cistern that is elevated and contains about 900 gallons of water or so. The cistern is probably 90 years old. The top is open with a screen covering it so it can also catch rainwater.
In a small room underneath the cistern is a water filter about the size of a large automotive oil filter. It is clear so you can see if it needs changing or not. To my amazement, the filter remains perfectly clean for about 8 months or so. They only need to change it annually. This is the water supply for the entire house.
The only downside is that when we have drought conditions the water in the underground spring drops and you can end up having a low water supply. There have been times when the pickup for the underground water is out of water and all you have left is the cistern.
The cistern is located slightly uphill from the house, so you always have great gravity fed water pressure.
As a side note, another underground spring pops up on their property. It's like a small stream about 6 feet deep or so.
The water is perfectly clear, and should I say COLD! I've swam in it before and even on a 100F day, it's almost too cold to get into.