REPORT OF INVESTIGATIONS No. 40 43


For example, the lowest average flow for a 1-month period was 60 cfs
(38.8 mgd). The upper curve shows the longest period of time that a
specified flow was deficient. The curve shows, for example, the longest
period that the flow was 60 cfs or less was 10 consecutive days.
 The curves shown in figure 25 can be used to determine if the flow


 10,000
 8000 -
 6000
 5000

 4000 -
 4000 Maximum period
 2000 of deficient flow


 1000
 800 -
 600 -
 400
 300

 200


 100
 80
 60
 50

 30 Lowest average flow
 n for indicated period
 20 -


 S 2 23 568 1 24364872
 1 2 3 4 6 8 10 20 1 2 3 4 56 8 12 18 24 36 48 72


CONSECUTIVE DAYS


CONSECUTIVE MONTHS


Figure 25. Discharge available without storage, Pine Barren Creek near Barth,
 1952-61.


is sufficient for a particular use without storage. If storage is needed, the
amount of storage required can be determined from the mass-flow curve
given in figure 26. The volume of water required in a reservoir can be
determined by superimposing a line representing the required rate onto
the mass curve at such a position as to give the maximum distance be-
tween mass curve and the flow-required line. The maximum distance
represents the amount of storage required, excluding losses by evapora-
tion and seepage.