Lows are assigned to each day of the water year for each state in each system. Low points (combinations of date and value) are entered into the “Lows” table. HEC-RPT interpolates between these known points using either a linear method, which connects known points with a straight line of average daily values, or a step method, which holds lows at the value of the last known point until the date of the next point is reached and then lows step up or down to the value of that next point. Description fields are provided for the whole lows category, where general approaches can be documented, as well as for the individual low points, where strategies for different points can be detailed. Choice of method is controlled by the radio buttons in the "Lows" area of the user interface (Figure 10).
Figure 9. New states appear as colored lines along the X-axis of the main plot.
Figure 10. Lows are displayed for each state.
Dry year values are highlighted in the figure and plotted in orange. Wet years (in green) and average years (in red) each have only two data points, 0-cfs on 01Oct and 20-cfs on 01Jan. The difference between the two is that wet is using the linear interpolation method and average is using the step interpolation method.
To support plotting of lows, zero flow points are used at the end of each water year for the linear method. To avoid seeing that zero point in plots, a low value for that date needs to be specified in the table.