Explanation

The Percentage of Stations Below Normal, plotted as the red line on the above graphs, is calculated each day as the percentage of streamgages reporting below normal flow, where the lower bound for normal is the 25th percentile value among all historical values for the day of the year. The percentage of stations below normal is based only on streamgages in the state (or water resource region) having at least 30 years of record.

On this graph, the 25th percentile value is based on historical values for the day of the year.

Important Note: Gaps in the red line occur on days when less than two-thirds of the maximum number of stations in the state report data. On these days, confidence in the plot value is substantially reduced, and may even misrepresent actual conditions. To avoid potential bias in the presentation, no value is plotted for these days. The loss of data is usually related to equipment failure, computer problems, or telecommunications difficulties. Occasionally, widespread flooding events can disrupt data acquisition at a large number of stations.