The Supply and Uses of Water 225 



F. The watershed. What is its extent ? The character of the 

 ground, sand, clay, gravel, rock, or loam? What kinds of vegeta- 

 tion grow on the watershed? What is the approximate amount of 

 the weed type? About how much decaying vegetable matter is 

 produced annually ? Does much of the vegetation produce spores or 

 pollen ? Do you think spores or pollen make water less safe for drink- 

 ing and domestic use? Cf. pages 197,220. Is the area inhabited 

 by animals ? What kinds and how many ? Is it occupied by people ? 

 About how many ? What do the people dwelling there do with refuse 

 and sewage ? Are any of the lands under cultivation ? What fertilizers 

 are used on such lands ? How could this affect the water supply ? 



G. Is the water purified? If done by a storage reservoir, describe 

 the location and other important features of the reservoir and state 

 how long water is stored before distribution. See page 219 for propor- 

 tion of bacteria killed by still water storage. If there is a filter system, 

 describe it, giving size and capacity, arrangement of materials through 

 which water is filtered, amount delivered in twenty-four hours, super- 

 vision and other interesting features. Compare action of a sand 

 filter with that of a household filter. What percentage of bacteria is 

 removed by a sand filter? Are chemical substances used to sterilize 

 the water? If so, what kind? Is the water tested regularly? How 

 often? Has any epidemic such as typhoid fever been suspected as 

 due to, or positively traced to, the contamination of the water supply ? 

 What facts support the conclusion? How was the water polluted? 

 What was the source of the pollution? Give a summary of the chief 

 impurities, both dangerous and harmless but undesirable, which may 

 be found in water. 



H. The sewage system. What is the local method of sewage dis- 

 posal? What is the relation of the place where sewage is emptied 

 to the source of water supply for your own and neighboring com- 

 munities? If cesspools are used, are they so located as to avoid pol- 

 lution of the water supply? If a sewage disposal plant is in operation, 

 describe its general plan and operation. What disposition is made of 

 the product of such a plant ? 



IX. WATER PRESSURE 



Practical importance of water pressure. Water supplied 

 within the same system has different rates of flow or different 

 pressures at different places and elevations. The feeble, slow 

 trickle from a faucet on the third floor or higher is frequent in 



