We put in a concrete cistern when we moved into our house 11 years ago. It's been a great help for our garden since we're on a well. Any rain we get is channeled from the gutters on half our house into the cistern. We just had two inches of rain. That amount will fill the cistern, but when we went to use it, only a few inches was in the bottom of it. I can't figure out what's happening. It must have developed a leak because I can't figure out what else could be wrong. If you have any experience with this, I'd sure appreciate your thoughts.