There is no other planet like Earth in our solar system: no other planet is both rocky and has flowing water at its surface. Without water, life as we know it could not exist. Although our planet is covered by seemingly vast oceans, only a small fraction of the water on Earth is fresh, and even less is readily accessible. As the population grows, it becomes more important to understand how to manage and protect our fresh water supply.

Water is very useful. It generates electricity and waters the grains, fruits and vegetables that people and animals eat. It can also be very dangerous, causing much destruction from flooding and landslides. Concern about the purity of both surface and groundwater is a growing issue. If we misuse chemicals on our crops, lawns, or industry both surface and groundwater supplies may be contaminated.