Chapter 13 Water Resources

Transcription

1 Chapter 13 Water Resources Where does your drinking water come from? I. Earth s Water Supply A. Where is Earth s water? % - oceans % - icecaps and glaciers % - surface or groundwater B. Earth s supply of fresh water is continuously being renewed through the water cycle 1. Definition the movement of water from the oceans and freshwater sources to the air and land and finally back to the oceans 2. Processes: a. evaporation from surface water, soil and organisms b. condensation air containing water vapor cools and forms clouds c. precipitation rain, sleet, snow, or hail i. may run-off into surface water ii. may infiltrate into groundwater Review Questions 1. What percentage of Earth s water is available to us as fresh water? 2. Draw a simple diagram of the water cycle and label the 3 main processes.

2 II. Surface Water A. Running Water 1. Includes rivers and streams 2. May enter through surface run-off from the surrounding watershed (the land area from which surface run-off drains into a system of rivers and streams) B. Standing Water 1. Includes lakes, ponds, wetlands (ie. swamps and marshes), and reservoirs 2. Form when run-off gets caught in low places, or by artificial means III. Groundwater A. Water continues to move downward after it hits the ground, through permeable layers of soil and rock, then stops moving when it reaches an impermeable layer of rock B. Water table the level below which the ground is saturated with water 1. May be high in some areas (ie. near the sea, or in low-lying forests), and deep in others (ie. deserts) 2. Depth may change with precipitation, drought, or overuse of wells C. Aquifers layers of rock or sediment that allow groundwater to pass freely; sources of groundwater 1. Rate of movement varies with amount of precipitation, porosity of the rock, and slope of the aquifer 2. Groundwater may leave the aquifer and become surface water at the zone of discharge, may pump out on its own (when under pressure) through an artesian well, or may be accessed by drilling wells

3 Review Questions 1. What is a watershed? How does water get from a watershed to a river? 2. Describe how groundwater forms. 3. What causes the differences in the depth of the water table? 4. Name 3 ways that we may obtain water from an aquifer. IV. Uses of Water A. Residential use 1. The average person in the U.S. uses about 300 L of water each day 2. Uses include personal hygiene, cleaning, flushing toilets, gardening/landscaping, car washing, and recreational activities B. Industrial use 1. About 44% of all fresh water is used by industry 2. Uses include transporting goods, disposal of waste, generating power, cooling machinery, mining and refining natural resources, manufacturing raw materials, and producing synthetic materials C. Agricultural use 1. The single largest user of water in the U.S. (almost ½ of all freshwater use) 2. Irrigation the process of bringing water to an area for use in growing crops

4 Review Questions 1. Compare your daily residential use of water to that of a person in a developing country (like Kenya). What ways do you use water that they probably do not? 2. Make a list of all of the ways that you have used water so far today. Don t forget to include industrial and agricultural uses! V. Water Resource Problems A. Overdraft 1. Occurs when a body of water is drained faster than it is filled; may occur in surface water or groundwater Ex. The Ogallala aquifer is the largest aquifer in the world and supplies water to 8 midwestern states; the water in this aquifer is expected to last only 40 more years 2. Other problems with overdraft a. intrusion of salt water into freshwater aquifers b. subsidence, or sinking, of bedrock B. Habitat degradation or destruction 1. Includes water diversion (changing stream courses), building dams and reservoirs, and draining wetlands 2. Damages or destroys habitat of aquatic organisms such as fish, amphibians, and invertebrates, as well as migratory birds

5 Review Questions 1. What is overdraft? What causes overdraft? 2. Why do humans change stream courses, build dams and reservoirs, and drain wetlands? 3. What do humans need to do in order to solve some of our water resource problems? VI. Water Treatment A. Removing Salts 1. The process by which salts are removed from the water is called desalination 2. Methods: a. Distillation water is heated to boiling so water evaporated but salt remains; water vapor is cooled and fresh water collected b. Reverse Osmosis- salt water is forced through a strainer that traps the salt and lets the fresh water pass c. Freezing salt water is frozen and separates, forming an ice and brine slush; ice can be melted to obtain fresh water B. Water Purification 1. This process removes harmful chemicals and microorganisms that make the water unpotable, or unfit to drink 2. Process: a. Screening traps and removes large debris from water

6 b. Sedimentation i. water passes to large settling tanks where particles suspended in the water settle to the bottom as sediment ii. chemicals called coagulants may be added to cause the particles to clump together and aid in settling c. Filtration water is passed through a filtering material such as fine sand to remove smaller particles d. Aeration i. water is exposed to air and sunlight by allowing it to spray into the air or flow as a waterfall ii. bacteria enter the water and break down organic matter and oxygen is mixed in; this process improves the smell and taste of the water e. Sterilization water is exposed to extreme heat or chemicals such as chlorine in order to remove harmful bacteria and microorganisms Review Questions 1. If the ocean was your only source of water, what process could remove the salt so it would be drinkable? Describe how this might be done. 2. What does unpotable mean? 3. Name the 5 steps of the water treatment process.

7 renewed through Water Resources Water Cycle sources problems include with use include Surface Groundwater Overdraft Habitat Water degradation such as also called leads to Lakes Rivers Aquifers Subsidence Saltwater intrusion uses include Residential Agricultural Industrial

8 (from Mecklenburg County State of the Environment Report, 2002)

9 Where does your drinking water come from? (created by Shari Mudd and Cindy Kendrick) In the Mecklenburg County area, water can easily be taken for granted since it is so plentiful and relatively inexpensive. However, our water is the lifeline of our community and should not go unnoticed or unappreciated! Part I: Mecklenburg County s water supply Study the diagram on the attached page, and then answer the questions. 1. Where does most of the system s water come through? 2. How many gallons of water a day are pumped through this station? 3. Where does the water go when it leaves the pumping station? 4. How many gallons of water per day can be treated? 5. What are large water storage tanks called? 6. How many miles of underground pipe distribute water to the city? 7. Briefly describe how the water is distributed. 8. Who are the residential customers that the water is supplied to? 9. Name 2 of the county s largest users of water. 10. How does the city know how much water each home uses in a month?

10 Part II: Modeling Water Treatment In order for water to be purified for drinking, it must go through a series of steps to remove particles, organic material and living organisms. Name the 5 steps of the water purification process as outlined in your notes: In this lab, we will model some of the stages of the water purification process on a sample of pond water. Materials pond water filter paper cheesecloth gravel or sand 1 tsp. alum plastic bottle funnel beaker Procedure and Observations 1. Observe your sample of pond water and describe the contents. What do you see in the water? What color is it? How does it smell? 2. Begin the filtration process by removing any large particles from your sample of water.

11 3. Cover a beaker with 2 layers of cheesecloth, then pour your sample through the cheesecloth into the beaker. This process represents the 1 st filtration. How effective was the 1 st filtration? What types of material were removed from your sample? 4. Add 1 tsp. Alum to your sample. Alum is a coagulant. What is the purpose of a coagulant? How did it affect your sample? 5. Fold the filter paper so that it fits into your funnel, then add gravel or sand to the funnel. 6. Pour the sample through the funnel containing gravel and collect it in another beaker. This process represents the 2 nd filtration. How effective was the 2 nd filtration? What does your water sample now look like? 7. Pour your sample into a plastic bottle with a lid. Make sure that the bottle is not completely full. Shake the bottle vigorously. 8. Pour the water out of the bottle into a beaker. Pour the water back and forth between 2 beakers for a total of 10 times. This process represents aeration. How has your sample changed? (hint: don t forget to smell the water!)

12 Analysis and Conclusion: 1. Compare and contrast your water sample from the beginning of the activity to the end. How has it changed? Has anything remained the same? 2. Which step did we omit from our model of water treatment? Why is this step so important in reality? 3. Would you consider your water sample safe to drink now that we have purified the sample? Why or why not?

13 Chapter 13 Water Resources Day Activity Homework 1 Notes I Water, Water Everywhere Demo. * Notes II, III Get the Ground Water Picture * Ground Water analysis 2 Notes - IV Water we going to do? * Notes V, VI Where does your drinking water come from? Part I 3 Where does your drinking water come from? Part II Test / Assessment * found in supplemental activities SCOS Goal 4.04 Evaluate Water Resources