The Water Cycle: The Water Cycle Introduction to Aquatic Science Objectives: Objectives The student should understand the various phases of the water cycle. The student should have an idea of the impact on the environment if the cycle should be interrupted. The student should be able to communicate society’s need for clean potable water. An Introduction: An Introduction The Water Cycle: The Water Cycle Animated Water Cycle The water cycle is that path through the environment that water follows as it travels from its origins as precipitation to its destination in a lake or ocean. The water cycle acts as a filter to purify the water we need in order to survive. The Water Cycle: The Water Cycle Precipitation: Water falls from the sky in the form of rain, snow, sleet, or hail. The predominant weather patterns in an area determine how much water is available to that environment. Evaporation: The process where by liquid water becomes a vapor. The process is fueled by energy from the Sun. As liquid water is warmed the energy of each individual molecule increases. Over time the molecules are able to escape the surface tension of the body of water they are contained in and rise up into the sky. The Water Cycle: The Water Cycle Condensation: As evaporated water rises, it cools and looses energy. When enough cooling has occurred, the water molecules coalesce back into liquid droplets. We see these droplet collections as clouds. Transpiration: Water is taken up by plant roots and used in the plant metabolic process. Once the water has served its purpose, it is exhaled in the form of water vapor. It rises along with evaporated water from the Oceans and lakes to condense into clouds. The Water Cycle: The Water Cycle How much water is there to work with? The Total amount of water on the Earth 332.5 million cubic miles 97% is in the oceans (321,000,000 cubic miles) 2% is in the polar ice caps 0.6% is in underground freshwater 0.01% is in rivers and lakes 0.001% is in the atmosphere The Water Cycle: The Water Cycle The only water we have easily available to us is that found in lakes, streams, and some underground. We need clean water to survive. The water cycle process purifies as well as replenishes the water in an area. During run-off, as water seeps into or INFILTRATES the ground, solids and bacteria are removed. As various minerals are dissolved, chemical pollutants can be neutralized. The Water Cycle: The Water Cycle As water evaporates, salt, minerals, and impurities are left behind. Unfortunately, as it falls through the atmosphere, it can pick up pollutants along the way. At one time, rain water and water directly from lakes and streams was safe to drink. As our society has industrialized, the amount of chemical contamination in open ground water has become to high to be safe. Lake or stream water should be filtered and purified by chemical means before being consumed. The Water Cycle: The Water Cycle Potable: Water that can be used for drinking or cooking. In order to make water potable we must be concerned with particulate matter, chemicals, and microorganisms. Our water purification process must deal with all three. Commercial water filters (Brita for example) can deal with particles and some microorganisms but fail to clean out foreign molecules or very tiny living things. The Water Cycle: The Water Cycle In order for water to be safe to drink, it must be filter and then chemically purified. Most sporting good stores and hunting outfitters sell iodine tablets, for example, that work very well to neutralize harmful chemicals and microorganisms in water. At the least, water should be boiled 10 minutes after filtering before it can be considered safe to drink. An activated charcoal filter will also absorb many chemical pollutants.