Here's a little something about DC that I didn't know until I was doing some research for my last post about the fish in the Tidal Basin. There are two channels into the Tidal Basin, one for incoming water, the other for outgoing water. The one above leads to the Potomac River, and as the tide is rising, the gates open to allow water to enter the basin. On the other side of the basin is the gate below. The rising tide on the other side of this gate, in the Washington Channel, forces those gates closed. As the tide goes back down, the flow reverses. Higher water levels in the basin force the gates to the Washington Channel to open, thus flushing debris and sediment from the otherwise flow-free channel. I had no idea that all of this existed, I just thought the gates underneath the bridges were there to keep pleasure boats out of the Tidal Basin. See what you can learn!