The water cycle is the system which unites our understanding of how water and the atmosphere interact with Earth’s surface (or lithosphere). Remember the discussion of systems from the first lecture. The water cycle is a closed system on Earth. No water leaves the system, and the water cycle recycles: the outputs of the water cycle become the inputs of the water cycle. The water cycle is the basis for our discussion on surface water, glaciers, and the atmosphere. Consider the following stocks (areas water is stored) and flows (means of water movement) within the water cycle: (See Figure 12.2 in your textbook.)
| Stocks | Flows |
|---|---|
| Clouds |
Runoff (including streams) |
| Groundwater | Infiltration |
| Glaciers | Precipitation |
| Oceans | Evaporation |
| Interception (Plants and Animals) | Transpiration |
Look at how the arrows in figure 12.1 show the movement of water from each stock into another. Each of the stocks is separately fed by the inputs and output flows; yet, they are all connected to each other. The output of a glacier melting becomes an input to rivers and groundwater. The output of rivers is an input into the oceans. The output of evaporation of oceans becomes an input for clouds. If we were to put a picture of you as a “stock” -- you’d be a part of the “Interception” stock -- in Figure 12.2, can you draw the input and output arrows that would show how water moves into you and out of you to be recycled within the water cycle?
In the rest of this lecture, we will examine in more detail:
- Water Resources: Water Cycle, Groundwater, Water Issues
- Glaciers: Glacial Processes, Glacial Deposits, Indiana Glaciation
- Atmosphere: The Atmosphere and Climate