sea level
the level of the surface of the ocean
salinity
a measure of the amount of salt in water
aquifer
the layer of rock and soil that groundwater flows through
water table
the top level of the groundwater in an aquifer
watershed
the area from which water drains into a river
reservoir
usually an artificial lake that forms behind a dam
water cycle
the repeated movement of water through the environment in different forms; also called the hydrologic cycle
condensation
the process by which a gas becomes a liquid
evaporation
the process by which a liquid becomes a gas
precipitation
the water that falls from clouds as rain, hail, sleet, or snow
sleet
the frozen raindrops that fall as precipitation