Duration and current conditions graphs are two ways to characterize the hydrologic status of Pennsylvania streams and ground-water depths with respect to time and above normal, normal, or "drought" conditions.
The duration graphs, linked to below, are plots of the current 30-day moving averages of streamflows or depths to water below land surface as compared to historical data collected at the selected sites. The 30-day moving averages are superimposed as black, solid lines on graphs that display the historical data as: the 25- to 75-percentile flows or depths (normal conditions) in a green band; the 10- to 25-percentiles (drought watch conditions) in a yellow band; the 5- to 10-percentiles (drought warning conditions) in an orange band; and the 0- to 5-percentiles (drought emergency conditions) in a red band. Whenever the black line on a graph is above the green band, the 30-day moving average flow or depth is above normal. Whenever the black line is below the red band, the 30-day moving-average flow or depth is less than the previously recorded low. Note: Due to smoothing of the curves, the boundaries of the bands shown on the graphs represent approximate, rather than actual 25, 75, 90 and 95 percentile and record low values.
The current conditions graphs, linked to below, are plots of recent instantaneous flows, stages, or depths recorded at the selected sites. Medians for the period of record may be displayed on the flow graphs. Funding for this particular display of drought-related hydrologic data and continuing funding to maintain and enhance the display of these data are being provided by the Pennsylvania Department of Environmental Protection and the U.S. Geological Survey.
To view the duration and current conditions graphs, select one of the links below.
Streamflow Duration and Current Conditions Graphs
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| District Chief U.S. Geological Survey 215 Limekiln Road New Cumberland, PA 17070-2424 |
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