1. The document discusses two methods for determining the required balancing storage capacity of a distribution system: the mass curve method and hydrograph method. 2. The mass curve method involves plotting cumulative water demand against time to create a demand curve, and cumulative supply against time to create a supply line, and determining the maximum difference between them. 3. The hydrograph method involves plotting hourly water demand over 24 hours to create a demand hydrograph, assuming uniform pumping at the mean hourly rate, and measuring the area between the curves to determine required storage.

1. DISTRIBUTION SYSTEM

35.  This Balancing storage can be work out by means of,
1. Mass curve method
A mass curve is the plot of accumulated inflow or out flow versus
time.
Following steps are followed to find the capacity of reservoir by
using mass curve method.
1.From the past records determine the hourly demand for all 24
hour for typical days.
2.Calculate the cumulative demand and plot it against time. This
will give mass curve of demand.

36. 4.If the pumping is continued for all the 24 hours
Of the day, the supply line will be straight line
Extending in diagonally across the diagram for
the whole day .
5.Repeat the procedure for all typical days(max., min and avg.) and determine the maximum storage require for the
worst day.
Total storage Required=A+B
3. If the pumping is continued for all
the 24 hours of the day, the supply
line will be straight line Extending in
diagonally across the diagram for the
whole day .
4. Repeat the procedure for all typical
days(max., min and avg.) and
determine the maximum storage
require for the worst day.
Total storage Required=A+B
A
B

37. 4.If the pumping is continued for all the 24 hours
Of the day, the supply line will be straight line
Extending in diagonally across the diagram for
the whole day .
5.Repeat the procedure for all typical days(max., min and avg.) and determine the maximum storage require for the
worst day.
Total storage Required=A+B
2. Hydrograph Method
 The hourly water demand is not constant throughout the
day.
 The demand is more during morning and evening and less
during other parts of the day.
 For a uniform 24 hour pumping rate will be equal to the
Mean hourly demand shown by line PQ
 The required storage is then obtained by measuring the
shaded area using planimeter.

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