Many people make the following mistake: Never use a piece of metal, like a wrench, to measure the levels in a water well. If you must, use a bottle — for example, from a Coke — on the end of a sturdy string. Drop it in the well and when it touches the water it will float. That gives you a reading for the static water level.
Once you have the static water level, you can jostle the bottle several times and it will fill with water. Then you can lower the bottle onto the well bottom. That will give you a measure of the total depth of the well. Subtract the distance to the water from the total depth of the well, and the difference will be the amount of water in the well.