USGS - Science for a Changing World Interstate Commission on the Potomac River Basin
U.S. Geological Survey -  Interstate Commission on the Potomac River Basin

 Ground-Water Conditions, Potomac River Basin

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   Explanation of the Conditions Map and How Current Status is Determined


The current status is updated monthly for each well by comparing the daily mean (average) water level collected on the 1st day of the month to the historical water-level data for that same well. The status is updated by USGS on the 1st of each month. As an example, if the conditions map was accessed and viewed onApril 24th, the “current status” would represent conditions on April 1st. If accessed and viewed on May 10th, the “current status” would represent conditions on May 1st

On the conditions map below, a well shown in green (current status = High) will have a water level for the most recent month in the top 25 percent of all historical water levels for that well. A well shown in red (current status = Low) will have a current water level in the bottom 25 percent of historical water levels for that well. A well shown in blue (current status = Normal) will have a current water level in the range between low and high, representing the middle half of all the historical water levels for that well. A well shown in black (current status = Not Calculated) does not have sufficient data to produce summary statistics. The categories used to evaluate current status (high, normal, and low) were chosen to provide a historical context in which to view current ground-water conditions. They do not represent any specific regulatory limits or criteria.

Example conditions map used to illustrate features:

sample map of the potomac river basin

 

U.S. Department of the Interior, U.S. Geological Survey
Ground-Water Conditions, Potomac River Basin
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Last modified on Friday, 04-Jan-2013 11:46:56 EST
The URL for this document is http://pa.water.usgs.gov/potomac/map_explanation.html