The water cycle and its environmental processes

Water Cycle

The water, or hydrological, cycle, is the continuous movement of water above, on, and below the earth. It is a natural process that, when balanced, regulates the available water on the planet in a way that is not only relatively consistent, but overtime will allow for a balanced ecosystem. The water cycle, in general, takes water from one reservoir or holding area (say clouds) and allows it to move into another through various processes. The actual cycle moves continually through the process of evaporation, condensation, and precipitation. The water cycle also helps regulate and control temperature, which in turn helps regulate weather patterns. The basic water cycle may be viewed as a four stage model:

Evaporation (transpiration) -- Heat from the sun warms water from rivers, lakes, and the ocean to turn into vapor or steam; leaving the reservoir and moving upwards into the atmosphere. (Plants transpire, or lose water from their leaves).

Condensation -- As the evaporated water vapor gets colder rising into the atmosphere, it changes back into different levels of liquid -- clouds of different types.

Precipitation -- Depending on the temperature, season, type of cloud, and other conditions, precipitation occurs when the water that has evaporated becomes so heavy the clouds cannot hold it anymore and it falls back to earth as rain, hail, sleet, or snow.

Collection -- As precepitation falls, it may move into bodies of water or on land. If it hits land, it soaks into the earth and becomes part of ground water used by plants and animals, or run over the soil and collect in lakes, rivers, streams, etc., or filter through the earth and move back into the ocean.

The idea of the Water Cycle lends itself quite well into an Instructional Model Phase Summary:

Phase

Definition

Application to Water Cycle

Engagement

Considers prior knowledge and helps engage in new concepts using shorter activities that promote curiosity.

Questions: Where does rain come from? Why are some areas of the earth wet and some dry?

Actvities: Depending on level; analyze components of water and make a Venn Diagram showing importance, properties, and applications.

Exploration

Common activities that fuel conceptions, misconceptions, processes and skills (lab work).

Questions: Why are there different forms of precipitation? Why would it make sense that the water cycle regulates the amount of water on earth?

Actvities: Analyze different forms of precpitation by following a drop of water through water cycle. Why is it important that some water be stored in ice or snowpacks? (See: http://www.proteacher.com/redirect.php?goto=5347)

Explanation

Focuses on a particular aspect of experience and demonstrates conceptual understanding.

Questions: Does salt water act the same way as fresh water in the water cycle?

Activity: Place appropriate terms for water cycle in visual representation, as the one from the U.S. Geological Survey. (3 stage learning technique; identification, understanding, evaluation/explanation). See: http://www.proteacher.com/redirect.php?goto=5347

Elaboration

Challenge and extend conceptual understanding and skills through new, deeper, and broader activities.

Questions: What impact has civilization had on the water cycle? Are there dangers to irrigation or transforming arid areas into agriculutural areas? What about the polar ice caps?

Activities: Using gained knowledge, chart the amount of water it takes to grow a single hamburger, then research the number of burgers sold in your city; extrapolate to state, nation, etc. -- is this a good use of water?