Water Cycle - KEY Why is it important to keep the Earth’s water clean?
Why? The law of conservation of mass states that matter cannot be created or destroyed. This law means that the amount of water that is on Earth today is the same amount of water that was on Earth when the first fish crawled out of the oceans and the same amount as when the dinosaurs roamed the lands and the same amount that will be present long after humans are gone. This water recycles through the environment making its way through various reservoirs in the water cycle.
Model 1 – The Water Cycle
1. What do the dotted arrows represent? PROCESS OF WATER MOVEMENT IN THE WATER CYCLE
2. What are two processes that covert water into vapor? EVAPORATION AND TRANSPIRATION
3. How does water return to the oceans from the land? GROUNDWATER FLOW AND RUNOFF
4. Rain, sleet, and snow are examples of which process? PRECIPITATION
5. Using your prior knowledge and the diagram, what is runoff? RUNOFF IS WATER RUNNING DOWN A SLOPE ON THE SURFACE OF THE EARTH.
6. Using your prior knowledge and the diagram, what is infiltration? INFILTRATION IS WATER SEEPING INTO THE GROUND FROM THE SURFACE.
7. Using your prior knowledge and the diagram, what is condensation? CONDENSATION IS WATER VAPOR (GAS) THAT CHANGES TO A LIQUID STATE.
8. Which processes do not involve water entering nor leaving the atmosphere? INFILTRATION, GROUNDWATER FLOW, CONDENSATION, AND RUNOFF
9. What is the largest reservoir on Earth? OCEANS
10. Which of the processes might be responsible for helping to clean or filter water? Why? ANSWERS MAY VARY. (EX: EVAPORATION WILL LEAVE THE POLLUTANTS BEHIND AS THE WATER BECOMES GAS.)
11. Which processes might contribute to the addition of pollutants to rivers, lakes, and oceans? Why? ANSWERS MAY VARY. (EX: RUNOFFS CAN BRING POLLUTANTS DOWN INTO THE LAKES AND OCEANS.)
12. The water cycle is a “closed system,” meaning no water enters or leaves the system. What does this say about the importance of keeping the water on earth free from pollution? ANSWERS MAY VARY. (EX: POLLUTANTS MAY FOLLOW THE WATER THROUGH THE WATER CYCLE. THIS MAKES THE POLLUTANTS DIFFICULT TO REMOVE. SINCE WE HAVE A LIMITED SUPPLY OF WATER, WE MUST TRY TO KEEP IT CLEAN AND FREE OF POLLUTION.)
Read This! Reservoirs are locations where water can be stored before proceeding through the water cycle. For example, clouds are reservoirs for water vapor until the process of precipitation brings the water to the land where it can be stored in another reservoir, lakes. The amount of time water molecules remain in a reservoir is called the residence time.
Model 2: Residence Time at Different Reservoirs
Residence Time Residence Time Reservoir Reservoir (average) (average) Oceans 3,000 to 3,230 years Groundwater: Shallow 100 to 200 years
Ice Caps 10,000 to 100,000 years Groundwater: Deep 10,000 years Glaciers 20 to 100 years Lakes 50 to 100 years
Seasonal Snow Cover 2 to 6 months Rivers 2 to 6 months Soil Moisture 1 to 2 months Atmosphere 9 days
13. On average, how much time does a water molecule spend in the ocean? 3,000 TO 3,230 YEARS
14. On average, how much time does a water molecule spend in the soil? 1 TO 2 MONTHS
15. Which reservoir keeps water molecules for the longest period of time? ICE CAPS
a. Why do you think this is the case? ICE CAPS ARE FROZEN WATER MOLECULES; THEREFORE THE WATER MOLECULES CANNOT CONTINUE ON IN THE WATER CYCLE.
16. Which reservoir keeps water molecules for the shortest period of time? ATMOSPHERE
b. Why do you think this is the case? THE ATMOSPHERE CAN ONLY HOLD SO MANY WATER MOLECULES. AFTER THERE IS TOO MANY, THE WATER WILL FALL AS PRECIPITATION. THIS PROCESS TAKES PLACE IN A SHORT AMOUNT OF TIME.
17. How would a water molecule leave the groundwater reservoir and where would it go? (Hint: refer to Model 1) THE WATER MOLECULE WOULD LEAVE THE GROUNDWATER THROUGH GROUNDWATER FLOW TOWARDS THE OCEAN. IT COULD ALSO EVAPORATE INTO THE ATMOSPHERE.
18. Why would water in shallow groundwater have a shorter residence time than deep groundwater? SHALLOW MEANS THE WATER MOLECULES ARE CLOSE TO THE SURFACE MAKING EVAPORATION EASIER AND FASTER. ALSO DEEP GROUNDWATER MIGHT HAVE LESS SPACE OF THE WATER MOLECULES TO FLOW THROUGH (GROUNDWATER FLOW).
19. The residence times in the table are averages, but the range of time can be very large. Explain why a water molecule might spend a short time (1 month) in the ocean even though the average time is 3,000 years. WATER MOLECULES THAT ARE CLOSER TO THE SURFACE WILL EVAPORATE QUICKLY (MONTHS) WHILE MOLECULES DEEPER IN THE OCEAN WILL TAKE LONGER (YEARS).
Read This! Animals are an important reservoir for water too. Animal bodies consist of over 75% water and animal uses for water can impact the processes and the reservoirs of the water cycle.
20. In Model 1, draw and label arrows to and from the animals in the diagram to show how they are a part of the water cycle. ANSWERS MAY VARY.
21. If there is a large population of animals living near a lake, describe what impacts this could have on the entire water cycle. ANSWERS MAY VARY. (EX: ANIMAL WASTES CAN ENTER THE LAKES AND RIVERS THROUGH RUNOFFS.)