Why is there an inch of water in the neighbor's back yard?

When I was searching for a new house almost twenty years ago, I insisted that it have a swimming pool. Eventually I found the place we now live in and for the first ten years I enjoyed the pool that came with it. As the novelty of having a swimming pool wore off, I used it less and less. This last year I used the swimming pool exactly two times. My tenants used it zero times. It has become little more than the worlds biggest water bowl for cats, and the occasional toilet for raccoons. Yesterday afternoon around four, I noticed that the water level had dropped almost to the point that the skimmer wouldn't work, and the cats would have to hang by their toes to reach it for a drink. So I took the garden hose, dropped it into the pool, and turned it on. Here is how the thought process went. I would leave the hose running in the pool while I continued with my afternoon duties, but first I would go into the house and set the timer on my computer for thirty minutes so as to remind me to turn off the water. I figured that would bring the water level up about an inch.

Between ten and ten thirty at night, every night, I feed the cats outside and then walk my dogs. Last night when I opened the back door to feed the cats I heard a strange noise, sort of like Niagara Falls. How is it that I could forget, within just a few minutes, to set the timer on my computer to remind me to turn off the water? Well at least the cats, and the raccoons are happy.