HOW COMMUNITIES OBTAIN PURE WATER 



69 



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FIG. 108. OWENS VALLEY SYSTEM OF LOS ANGELES WATER SUPPLY 



the aqueduct five electrical generating stations have 

 been erected which furnish a total of 150,000 horse 

 power of energy. As the water falls it is made to turn 

 great turbines 1 which turn the electric generators. 

 Thus a great city has supplied its water and much of 

 its electricity by harnessing the water from the melt- 

 ing snows of the Sierra Nevada Mountains. 



In 1920 Los Angeles was consuming eighty million 

 gallons of water daily and in 1928 the amount had 

 increased to 150 million gallons daily. This is an in- 

 crease of 87 per cent in eight years. The Owens River 

 project is capable of supplying 2,000,000 people. Los 

 Angeles now has nearly 1,500,000 population and is 

 growing at the rate of about 100,000 per year. Soon 

 the present water supply will be inadequate and other 

 sources must be found. 



Engineers have already surveyed an area of about 

 18,000 square miles in an endeavor to locate the fu- 

 ture water supply of the city. The survey showed that 

 the Colorado River, 260 miles away, was the only 



1 Turbines, rotary wheel-like motors operated by the force 

 of currents of water under pressure. 



source which, could supply the demand. A gigantic 

 aqueduct to the Colorado that will supply 7,500,000 

 people in and around Los Angeles with pure water is 

 under construction. The project is scheduled for com- 

 pletion within a few years. 



Of what importance is pure water to the health of 

 a community? Thus far in the study of this topic you 

 have seen how various types of communities secure 

 pure water. It is not sufficient that just water be sup- 

 plied, but for good health the water must be pure. 

 Water supplies have frequently been the means by 

 which diseases were spread. Probably the most dan- 

 gerous disease from this point of view is typhoid 

 fever. In the following exercises you will secure some 

 first hand information bearing on this problem. 



Exercise. St. Louis secures part of its water supply 

 from the Mississippi River. The sewage of Chicago 

 reaches the Mississippi by way of the Chicago drainage 

 canal and the Illinois River. Study the graph (Fig. 107) 

 and answer the follozving questions about it in your 

 notebook. 



1. What was the death rate per 100,000 from typhoid 

 fever in St. Louis in 1870 f 



. 2. Can you suggest from the data of the graph why 

 the death rate dropped between 1870 and 1878? 



3. What years on the graph might be marked as epi- 

 demic years. 



4. Can you suggest a cause for the effect shown on 

 the graph between 1898 and 1903? 



5. What steps as shown in the legend of the graph 

 have been taken by the city of St. Louis to control this 

 situation? 



6. What evidence can you cite from the graph to sup- 

 port the assertion that this condition has been effectively 

 controlled? 



Exercise. // yon Twc in a rural area and secure your 

 water from a well or spring, make a careful survey of 

 your drainage conditions with respect to your water 

 supply by means of the following guide. If you live in 

 the city, survey some rural home which you have visited 

 or know about. 



1. Make a drawing in your notebook showing the 

 location of the well or spring with respect to the toilet, 

 the barn, and any other possible source of pollution. 



2. As shown in your drawing, is there any drainage 

 toward the water supply from the sources of pollution? 

 Which ones? 



3. If the source of supply is a well, zvhat type is it 

 dug or driven? 



4. Is the surface drainage sucli as ivaste water ade- 

 quately taken care of, or docs it drain back into the well?' 



5. What conclusions do you reach regarding the safety 

 of this water with respect to pollution? 



