48 SMALL WATER SUPPLIES. 



1 . Supplying a direct gravitational supply by means 

 of a dam forming a small reservoir from which the 

 water flows in a channel or pipe line. 



2. Providing sufficient power to a hydraulic ram, 

 raising either its own water or water from another 

 source. 



3. Providing power for a turbine which will drive 

 pumps for raising water or for other purposes for 

 which cheap reliable motive power is wanted. 



4. Providing water which is raised by other forms 

 of motive power. 



In cases Nos. 2 and 3 the power given out by the 

 flowing water will need to be ascertained, while in 

 cases Nos. i and 4 it may be also required to find 

 what quantity of water is flowing. 



Now, in small streams the quantity of water flow- 

 ing will vary greatly, and as the expense of a long 

 series of elaborate observations will not usually be 

 warranted by these small works in the same way as 

 is the case with large waterworks, it is the practice 

 of the writer wherever possible to make such gaug- 

 ings at the time of lowest flow. Unfortunately this 

 will only occur once a year, which may delay the 

 work somewhat, but nevertheless the course is ad- 

 vised unless any reliable information as to the lowest 

 level of the stream can be obtained, or the volume is 

 likely to be far and away in excess of what will pro- 

 bably be wanted. The information so often vouched 

 by gamekeepers, butlers, etc., on estates is usually 

 most unreliable. For small streams a very handy way 

 of gauging is by means of a small stone dam laid 

 across the stream, and made watertight with clay on 

 the inside. It is easily put up and removed ; a pipe is 



