Explain the Rippl Diagram or Mass Diagram
For a potable water reservoir, it is the simultaneous plots of the cumulative inflow and cumulative water consumption/demand, termed "draft" in units of volume (y-axis) vs. consecutive hours, days, months or years (x- axis). In these types of problems, water demand will be at a constant rate to generate a straight, constant sloped line on the plot.
The cumulative inflow will be a curved plot based on gains and losses to the reservoir. The storage volume needed is the separation between a trough (low point on the plotted curve) and a peak (inputs greater than the demand . At some high point on the plotted curve will indicate when reservoir capacity is full releasing water over the spillway may be necessary.