Water Science for Maryland, Delaware and the District of Columbia
May 2016 Water Conditions Summary
Many days of measurable precipitation led to above average precipitation throughout the Mid-Atlantic region and a record high monthly mean streamflow in Queen Anne’s County, Maryland. Precipitation also caused many groundwater levels and monthly mean streamflows to increase from the low April values.
In May, 68 percent (19 of 28 wells) of groundwater levels at USGS observation wells were normal (between the 25th – 75th percentiles) and 61 percent (18 of 33 sites) of the monthly mean streamflows were normal at sites used to monitor the response of water resources to changes in climatic conditions in Maryland, Delaware, and the District of Columbia.
Groundwater was above normal at seven USGS observation wells in Delaware and Maryland and below normal at two USGS observation wells--one in Harford County, Maryland and the other in Montgomery County, Maryland.
Monthly mean streamflow was at a record high at Sallie Harris Creek (Queen Anne’s County) in May and above normal in another 13 of the 33 streamgages used to monitor climatic conditions. Streamflow was below normal at a USGS streamgage in Prince George’s County.
*A percentile is a value on a scale from 0 to 100 that indicates the percent of a distribution that is equal to or below it. A percentile between 25 and 75 is considered normal. For example, a groundwater level in the 90th percentile is equal to or greater than 90 percent of the values recorded for that month.
To view more detailed information about Monthly Water Conditions in Maryland, Delaware, and the District of Columbia, use the navigation menu on the left.
Why is it important for the USGS to collect and analyze water resources data?
USGS water data are valuable to the public, researchers, water managers, planners, and agricultural users, especially during floods and droughts. These data can be used to assess how water resources respond to changes in climate. Scientists at the USGS have measured streamflow and groundwater levels in wells to assess water resources for over 125 years.
In addition to providing the most extensive set of historical streamflow and groundwater data available to the public, the USGS collects water data and quality-assures the data by employing standardized techniques across the country. The uniformity of the dataset allows for multi-state comparisons and other comparative statistical analyses that better inform policy makers of the possible water resource conditions they might encounter in the future.
The sites used in this water summary were carefully selected to show the response of streamflow and groundwater levels to precipitation. Ideally, these sites will show minimal effects from human influences. The streamflow and groundwater data are ranked in comparison to the historical record and summarized. Precipitation and reservoir data are also presented to give a more complete picture of the region’s water resources.