Since the time I was four or five years old, I played alone for many years (even when I was in college) building dams across a little stream that flowed over a small stony hill into our reservoir in our farm. I was crazy about this. I spent several hours during weekends and summer days when I was in my village with this activity. I was amazed at the force and nature of water flow. I would use little stones and mud I could gather and build a dam. It is not easy to build a dam across flowing water. As you build, some of it gets washed up. The size of stones and the way they are placed while building the dam is also important. Otherwise, the water forces out the mud and sand leaving huge holes through the stony dam making it useless. No matter how big the dam that you build is, eventually, the water from the stream fills up and overflows. So, you have to make arrangements for overflow without damaging the dam. It is such a thrilling experience to build a dam that is virtually impenetrabl...