1. The hydrologic cycle

2. Water Resources…
~93-97% in seas/oceans ~2-4% underground ~2-4% frozen ~ <.1% in rivers, lakes, atmosphere, living things

3. Water is constantly circulating between the oceans, continents and atmosphere in a system called the hydrologic cycle. This circulation is driven by a combination of the energy from sun, geological processes and gravity.

4. Water from the oceans and land is transported into the atmosphere by evaporation. Water is also transferred to the atmosphere from vegetation by evapotranspiration.

5. Water returns to the earth's surface by precipitation.

6. On land, some of this water flows over the surface in streams and rivers into lakes, reservoirs and the oceans.

7. The remainder infiltrates the land surface and percolates into aquifers. Some water can enter aquifers directly from the oceans.

8. The energy of the earth's interior drives the geological processes that influence formation, entry, storage, movement and reappearance of groundwater. Groundwater can be a source of surface water on land and can flow into the oceans.

9. What do the Numbers mean?