DISTRIBUTION OF WATER 200 



the loss h r , up to P = 5-^ r \(Q - q x}* dx 



* 



5- 



2 g m Q * 



|>* - Q 1* + I***"] feet, 



and since, if Q x is the flow at this point, Q = Q. T + <F> this can be 

 written 



F 2 



h x = 

 At the discharge end of the pipe line Q x = o; qx Q\ x = 



or the loss of head is one third that occurring in the same pipe line if 

 the flow were uniform instead of gradually diminishing. 



AKT. 81. DISTRIBUTION OF WATER. 



The consumption of water for domestic and trade purposes varies 

 largely from town to town. In Great Britain the domestic supply ranges 

 from about 18 to 25 gallons per head per day, while in the United States 

 the consumption ranges from about 40 to 200 gallons per day. During 

 the summer months the consumption per day may be as much as 40 per- 

 cent, greater than the average for the whole year. The hourly fluctuation 

 in demand necessitates a maximum rate of supply about 33 per cent, 

 greater than the average daily rate taken over 24 hours, so that the 

 supply pipes should be sufficiently large to give a temporary supply at 

 least 85 per cent, greater than the yearly average. It is usual to allow 

 for a maximum rate of flow equal to at least twice the mean rate to be 

 anticipated when reasonable increases of population have been taken 

 into account. 



In order to render the fluctuating run -off from the catchment area, 

 available for the fluctuating demand, a storage reservoir is necessary to 

 catch and store the run-off when in excess of the temporary demand, and 

 when the average monthly run-off and probable demand is known with 

 fair accuracy, the necessary volume of this may be calculated. Usually 

 the reservoir is at some considerable distance from the town to be 

 supplied, and to avoid laying down a long pipe line to supply water at 

 the maximum hourly rate demanded, and to minimise to some extent 

 the inconvenience caused by a possible break in this line, a smaller 

 " service " reservoir, capable of storing about three day's supply is 

 constructed as near to the town as is convenient, and, if feasible, at a 



