 Today, there are more than a billion people living without access to clean drinking water. And that's really hard for us to imagine on the east coast of the United States, where there's water everywhere. Today I'm standing in a stream near Lamont, Pennsylvania. And if I were here a hundred years ago, I would have readily taken a stop with this water and drunk it. But I'm not quite so sure about that today. There are factories around. There's farms around. And this water is probably not quite good enough to drink. This stream behind me is a tributary to the Chesapeake. And ultimately this water ends up in Chesapeake Bay. And if I can't drink this water here in rural Pennsylvania, can you imagine what it's like but by the time this water gets to the Chesapeake, it would definitely be a bad decision to drink the water flowing into the Chesapeake Bay today. The other part about being on the east coast of the United States is we're in a lush region. And climate change here is forecasted to make this region maybe a little bit more lush and a little bit higher rainfall in the future. We'll never have a problem with access to drinking water in this part of the world. But if we go out to the western part of the U.S., climate change forecasts predict that the region will become a lot drier. Communities out west in the U.S. are going to have to make really tough decisions as to how they manage their water resources. Such tough decisions have already been made in places around the world such as Australia where devastating droughts over the last few decades have led rivers to virtually reverse course and communities have had to make very tough decisions about how they manage their water resources. So in this module we'll learn a lot about how water behaves on the surface of the planet. What is going to happen in the future with climate change and the choices communities are going to face with windling water resources. Now enjoy it. Please get started.