The Supply and Uses of Water 205 



Shallow wells should be advantageously located and carefully 

 protected from pollution. 



Dams are often needed to secure a constant water supply for cities, 

 for agricultural purposes, for power, and for protection against floods. 



The construction of dams is still experimental, as the conditions are 

 peculiar and results cannot always be predicted. 



The Arrowrock Dam is typical of the dams constructed by the 

 United States Reclamation Service. 



REVIEW QUESTIONS 



1. Mention several uses of water in the household ; in the com- 

 munity as a whole. 2. Give several reasons for the community 

 control and supervision of water supply in towns or cities. 



3. What are the most desirable sources of water for cities? Give 

 reasons. 4. What has Los Angeles done to provide an adequate 

 water supply? Describe some of the important geographic conditions 

 which had to be met. 5. Give an account of the recently completed 

 water supply system of New York City. 6. What dangers are there 

 in taking water for drinking from untested streams? 7. How was 

 the water supply of Chicago affected by the construction of the drain- 

 age canal? 8. What provisions are made by London to insure a safe 

 water supply ? What seems to be the result of such precautions upon 

 the health of the city? 9. What unusual property is possessed by 

 the water of the Ganges River? How docs it differ from well water 

 of the region? 



10. What geological formation makes artesian wells possible? 



11. Why is artesian well water safe for drinking and domestic uses? 



12. What is the water level of ground moisture? Upon what does 

 it depend? How is it related to stream channels? 13. Describe tho 

 course of water through the earth until it issues as a spring or deep 

 well supply. 14. To what property does water owe its occasional 

 peculiar taste, odor, and character? 15. What makes some waters 

 hard and others soft? 16. What are the usual sources of supply in 

 rural sections? 17. What are the sources of danger in cistern water? 

 In shallow wells ? 18. Describe how fresh water comes from salt water. 



19. What is the proper location of a shallow well in relation to rock 

 layers, buildings, and drainage? 20. What sort of construction is 

 necessary to make the well reasonably safe? 21. How can the slope 

 of the subsoil be determined? 



22. Mention several purposes for which great dams are constructed. 

 23. What are some of the forces a dam must successfully resist? 



