Definition

The hydrosphere is often called the "water sphere" as it includes all the earth's water that is found in streams, lakes, the soil, groundwater, and in the air. The hydrosphere interacts with, and is influenced by, all the other earth spheres. The water of the hydrosphere is distributed among several different stores found in these other spheres. Water is held in oceans, lakes and streams at the surface of the earth. Water is found in vapor, liquid and solid states in the atmosphere. The biosphere serves as an interface between the spheres which aids in the movement of water between the hydrosphere, lithosphere and atmosphere. The hydrologic cycle traces the movement of water and energy between these various stores and spheres.

The Water Cycle

OVERVIEW

First the oceans. They hold about 97% of all the water on Earth. Water moves out of the oceans by EVAPORATION. When water falls as rain, it's called PRECIPITATION. So this goes on constantly. The water evaporates and then falls as rain. What about on land? About 85% of all evaporation happens over the oceans. The other 15% happens over the land from lakes, rivers and other bodies of water.

First we'll look at the water over the oceans. The water evaporates from the surface of the ocean. It floats upwards into the atmosphere (the troposphere to be exact). Then two things can happen: the water can fall down to Earth as precipitation or it can float through the atmosphere as vapor (that's called ADVECTION).

More stuff has to happen over the land. In addition to evaporation something called TRANSPIRATION happens. Transpiration is when water is taken from the living things like plants and animals. The water then moves to the atmosphere and can fall as precipitation or float around in the upper troposphere. If the water falls as precipitation, it can either evaporate again, move to groundwater or end up in rivers flowing back to the oceans.

LIFE OF A WATER MOLECULE

So you're a water molecule. Chances are you'll stay a water molecule and won't ever be broken down. The world likes to keep its water around. You're moving through the hydrologic cycle. You evaporate, fall in rain, and drain in a river. Not a lot of excitement. But how much time does it take? Scientists think that if you are lucky enough to be evaporated into a cloud that you spend about ten days floating around the atmosphere. If you're unlucky enough to be at the bottom of the ocean, or stuck in a glacier, you might spend tens of thousands of years without moving.

KEY TERM REVIEW:

ADVECTION: When an air mass moves over the ground in a horizontal/vertical direction and it is heated up. It can also happen other ways. It is always when energy is transferred as one air mass moves across another mass (air/water/land).

EVAPORATION: When water moves from a liquid state to a gas state without the water boiling.

TRANSPIRATION: When water moves from an organism back into the air. Plants lose water from their leaves. Humans lose water from their breath and skin.

How we use the Hydrosphere

While exercising you should be drinking between 5 to 12 ounces of water every 15 minutes, depending upon your body weight.

Interaction of the Hydrosphere

Quiz