March 2009 USGS Maryland-Delaware-DC Water Conditions Summary

During most of March, there was little precipitation until the last week. However, the rain was not enough to bring streamflow to normal levels. Streamflow at all of the stations used by the U.S. Geological Survey (USGS) to monitor water conditions across Maryland, Delaware, and the District of Columbia was below normal. Nine sites had the lowest March monthly mean streamflow on record and 27 sites were in the lowest 10th percentile. The low streamflow levels span across the region, even more than during the 2002 drought.

Groundwater levels were below normal in 21 of the 26 wells used by the USGS to assess response to climatic conditions. Water levels in 4 wells set new record monthly lows. Twelve wells were in the lowest 10th percentile, one above normal, and 4 at normal levels.

Early April 2009 Update

During the first 7 days of April, there has been 1.79 inches of rain at the weather station in Baltimore (National Weather Service). Most of the rain (1.55 inch) fell on April 3, 2009. Rainfall at Hagerstown, MD was 0.75 inch and was about an inch in Delaware and the District of Columbia. Precipitation levels across the region remain 3-6 inches below normal since the year 2009 began.

Streamflow and groundwater levels have responded to the recent rainfall. Streamflow at the Potomac River at Point of Rocks was at record-setting lows in March and has now climbed to above normal.

The hydrograph for the Potomac River at Point of Rocks shows 50 days of streamflow. The triangles indicate the median for that day for the period of record. Streamflow levels began to drop in February and continued to drop through most of March. Normally, streamflow increased at this time. At the end of March-beginning of April, streamflow rapidly climbed to normal, then above normal levels. USGS hydrologists will be watching to see how quickly the flow recedes.

Groundwater levels rose in response to the rainfall at the end of March-beginning of April. The water level in the well in Baltimore County, BA Ea 18, rose 0.21 inch. However, not all wells responded to the same degree as the well in Baltimore County. The real-time well in Kent County, Delaware has risen less than 0.05 inches during this period.

March 2009Precipitation

Precipitation in March was 1-2 inches less than normal at weather stations across Maryland, Delaware, and the District of Columbia, according to data from the National Weather Service. The dry March follows the driest February on record. The Hagerstown weather station, had the least amount of precipitation with only 1.4 inches, but this station does not have enough record to calculate statistics.

In March, all counties in Maryland had precipitation 1-2 inches below normal, except for Dorchester, Somerset, and Worcester which were less than an inch below normal (data from MARFC). Delaware and the District of Columbia precipitation was also below normal in March. Rainfall for the last 365 days remains in the normal range throughout Maryland, Delaware, and District of Columbia.

Source: National Weather Service
MD and DC: http://www.weather.gov/climate/index.php?wfo=lwx
DE: http://www.erh.noaa.gov/phi/
Middle Atlantic River Forecast Center: http://www.erh.noaa.gov/marfc/Maps/precip.html

March 2009 Streamflow

Nine of the 30 USGS streamflow stations used to assess climatic conditions in Maryland, Delaware, and the District of Columbia were at the lowest March monthly mean streamflow on record. One of those sites is the Potomac River at Point of Rocks where data collection began in 1895. Another 18 USGS streamflow stations had monthly mean streamflow in the lowest 10th percentile. The remaining 3 streams were also below normal.

The monthly mean streamflow for the Potomac River at Point of Rocks decreased sharply since December 2008 and was the lowest since record-keeping began in 1895. The 5-year hydrograph shows the monthly mean streamflow as a dark line and normal (between the 25th and 75th percentiles) as a white band.

Five-year hydrographs for these streams can be viewed at: http://md.water.usgs.gov/surfacewater/streamflow/

The table below ranks the lowest monthly mean streamflows on the Potomac River at Point of Rocks, three of which have been during the last decade.

March 2009 Groundwater

Groundwater levels were below normal in 21 of the 26 wells used by the USGS to assess climatic conditions in March. Wells in Carroll, Charles, Kent, and Montgomery Counties had the lowest March groundwater level on record. Water levels in the wells in Delaware were in the lowest 10th percentile. Groundwater levels rose to normal to above normal in Somerset and Wicomico Counties after several months of being below normal.

The water level in the well in Montgomery County, Maryland (see below) continues to be below normal and it is the lowest March measurement, breaking the previous record set in 2002. The 5-year hydrograph shows the water level as a dark line and normal (between the 25th and 75th percentiles) as a white band.

Five-year hydrographs for these wells can be viewed at: http://md.water.usgs.gov/groundwater/web_wells/current/water_table/counties/

March 2009 Reservoir Levels

Water available from the Baltimore reservoir system (Loch Raven, Liberty, and Prettyboy) dropped 0.24 billion gallons to 69.42 billion gallons in the available storage at the end of March 2009.

Water stored in the Triadelphia and Duckett Reservoirs, which serve Montgomery and Prince George's Counties, also showed little change in normal capacity at the end of March, 2009. The level in Triadelphia is being kept low for gate maintenance.

More Information

Maryland-Delaware-District of Columbia

USGS Drought Watch

USGS Water Summary

Streamflow

Groundwater

Chesapeake Bay

National

USGS Streamflow and Groundwater levels

U.S. Drought Monitor from the National Drought Mitigation Center

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Contact

U.S. Department of the Interior
U.S. Geological Survey

Wendy S. McPherson (wsmcpher@usgs.gov)
Maryland-Delaware-D.C. Water Science Center
5522 Research Park Drive
Baltimore MD, 21228
Phone:443-498-5555
Fax:(443-498-5510