Harassing Neighbor

[tmz1]

I just bought a house in a town that I am not all that familiar with yet. Since the day I moved in the old neighbor has been filing complaints on me about the use of water. My son plays with the hose since it is 105 degrees most of the summer and in the begining of spring. The water flows into an alley that is used by all of the surrounding neighbors at the back of my property. The water is not that bad, but the alley slopes downwards from both sides so that my property is at the lowest part of the ground. The water then gets stuck and I can't fix it. This happens even during the rainy seasons. I do not really even use the water that much. I just want to know what I can do to stop this harassment. I want to know if I am in the wrong. If I moniter my sons use of the water and I know it is not excessive will I still be found to be wasteful. How can I get him to leave me alone and give up and what can I do to make sure that local agencies know about the harassment? Thanks for your help