USGS Ohio Water Science Center

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Ohio Water Science Center

National Water Topics


USGS Water Science Centers are located in each state.

There is a USGS Water Science Center office in each State. Washington Oregon California Idaho Nevada Montana Wyoming Utah Colorado Arizona New Mexico North Dakota South Dakota Nebraska Kansas Oklahoma Texas Minnesota Iowa Missouri Arkansas Louisiana Wisconsin Illinois Mississippi Michigan Indiana Ohio Kentucky Tennessee Alabama Pennsylvania West Virginia Georgia Florida Caribbean Alaska Hawaii New York Vermont New Hampshire Maine Massachusetts South Carolina North Carolina Rhode Island Virginia Connecticut New Jersey Maryland-Delaware-D.C.

How Dry Is It?

How dry is it?

Exactly how dry (or wet) has it been lately? To help answer that question, duration hydrographs have been added as a new option under the drought watch pick list on the USGS WaterWatch Web page for Ohio. You can input a stream name or gaging station number and also select a 7-, 14-, or 28-day averaging  period. An example for a streamflow gaging station (the Scioto River at Prospect, Ohio) is shown here. The plot shows a trace of the running 7-day average streamflow (the black line beginning on January 1 of the previous calendar year) as well as colored bands that represent historical percentile ranges of streamflow for each calendar day.

In the example, the 7-day average streamflow for August 29, 2008 (the point where the black line ends on the right), can be seen to fall in the low end of the range of “normal” streamflows (where normal is defined as a value that is greater than or equal to 25 percent of the historically observed values and less than or equal to a value that is greater than or equal to 75 percent of the historically observed value, both for that calendar day over the station’s period of record). In contrast, streamflow was “much above normal” (defined as a value that is greater than or equal to 90 percent of observed values for that calendar day) around the second week of February 2008. 

It is worth noting that the entire period of record is used to compute the historical streamflow percentiles. Consequently, if streamflow regulation has changed during gage operation (for example, due to the addition of a reservoir), the percentiles will represent a mixture of streamflows from before and after the change in regulation. This can lead to an inaccurate characterization of flow conditions as compared to streamflows representing only current regulation.

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