While rivers make up just a fraction of the water on Earth, they provide the majority of what we use every day. Rivers run over and through our world, and sometimes we don't even know they are there. But do we fully understand or even appreciate all that rivers can do? All over the world, cities large and small were built near rivers because of what they can provide: drinking water, transportation, power sources. But over the centuries as cities grew, the rivers became polluted by sewage and ind