Flow into Chesapeake Bay near Record High Levels

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

Contact:
Wendy McPherson (wsmcpher@usgs.gov)
Maryland-Delaware-D.C. Water Science Center
5522 Research Park Drive
Baltimore, MD 21228
Phone:(443)498-5500
FAX: (443)498-5510

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Updated: August 6, 2003

Total flow into the Chesapeake Bay during July was the third highest since record keeping began in 1937 (66 years), according to hydrologists at the U.S. Geological Survey (USGS) in Baltimore. Above normal rainfall and cooler than normal temperatures for the last 3 months have kept rivers full and the water table high in Maryland and Delaware. Groundwater levels have dropped since June but remain above normal. Two wells reached monthly record highs in July. The high groundwater levels contribute flow to streams during the summer months.

During July, total flow into the Chesapeake Bay averaged 45.1 bgd (billion gallons per day), which is 83 percent above average (see http://md.water.usgs.gov/monthly/bay.html). This is the second consecutive month of near record high total flow into the Bay. The highest monthly Bay inflow for July was in 1972, which may have been residual effects of high water levels from Tropical Storm Agnes.

The downside of the increased streamflow into the Bay is that large amounts of nutrients and sediment are carried into the Bay, which has contributed to very low dissolved oxygen levels. The low dissolved oxygen levels harm fish, crabs, and other organisms in the Bay. More information about streamflow, water quality, and the Chesapeake Bay can be found at: http://md.water.usgs.gov/monthly/bay.html and www.chesapeakebay.net.

The monthly mean inflow graph shows that in 2003, the total flow into the Chesapeake Bay has been above average for each month except February. The current flow (heavy black line) remains above normal and was the third highest total inflow into the Bay since 1937. The inflow for July 2003 is three times higher than it was during the drought in July 2002.

Groundwater levels in wells used by the USGS to monitor climatic conditions in the bi-state region were at above normal levels, and two wells in Anne Arundel and Carroll Counties, Maryland were at their highest level in 40 years (shown as star symbols on map). Groundwater levels dropped in July, as expected during the growing season because of increased water demand by vegetation, but the groundwater levels remain elevated from the abundant rainfall during May, June, and July. For 5-year hydrographs of groundwater levels for the climatic indicator wells, visit: http://md.water.usgs.gov/groundwater/. In contrast, during July 2002, most of the wells and streamflow stations were at below normal levels, and 10 wells reached their lowest levels in more than 40 years.

The map shows that at the end of July 2003, all wells used to measure climatic conditions by the USGS were at above normal levels (dark circle symbol) based on more than 40 years of data. Two record high levels were set and are shown as a stars surrounded by a dark circle symbol.

Streamflow was at normal to above normal levels across Maryland and Delaware.

Rainfall either soaks into the ground, saturating the soil and recharging the aquifers, or if the ground is saturated, the excess water runs off into streams, resulting in high streamflow levels. With many groundwater and streamflow levels above normal, there is the potential for localized flooding (for information on flooding, see http://md.water.usgs.gov/faq/index.html#hydrologyoffloods.)

Streamflow levels were above normal at the end of July in most streams across Maryland and Delaware. Streams near the Pennsylvania border were at normal levels. The average monthly streamflow of the Potomac River near Washington, D.C. was 7.0 bgd (billion gallons per day), or 117 percent above normal (see graphs at http://md.water.usgs.gov/monthly/poto.html.)

Current and historical streamflow data can be monitored on the web at http://waterdata.usgs.gov/nwis/rt. Five-year monthly streamflow hydrographs from the USGS stream-gaging network can be viewed on the USGS website at http://md.water.usgs.gov/surfacewater/streamflow/.

High groundwater levels and above normal rainfall helped to keep reservoir storage levels in the Baltimore reservoir system and in the Triadelphia and Duckett Reservoirs on the Patuxent River at full capacity in July. Reservoir data graphs can be viewed at: http://md.water.usgs.gov.

The Water Resources Discipline of the USGS, in cooperation with Federal, State, and local agencies, collects and publishes a large amount of data pertaining to the water resources of Maryland, Delaware, and Washington D.C. each water year (October 1 to September 30). The resulting annual report documents hydrologic data gathered from the USGS’s surface-water and groundwater data-collection networks in each state. These data, accumulated during many water years, constitute a valuable database that can be used to develop an improved understanding of the water resources of the State. The water resource data are published annually in two volumes (surface water and ground water) and the 2002 Water Year is available at http://md.water.usgs.gov/publications.

Streamflow and groundwater levels are used to assess the current water conditions and can be used to predict the potential for flooding and drought conditions. These USGS data have been provided to State and local water resource managers and are critical for making appropriate decisions on water regulation. For more information on streamflow and groundwater levels in Maryland and Delaware, see Water Watch at: Water Watch.

The real-time streamflow stations used in this analysis are operated in cooperation with the Maryland and Delaware Geological Surveys, the Maryland State Highway Administration, the U.S. Army Corps of Engineers, the Maryland Department of Natural Resources, the Maryland Department of the Environment, Baltimore County, and other agencies. The observation wells used in this analysis are operated in cooperation with the Maryland and Delaware Geological Surveys. The real-time wells are operated in cooperation with the Maryland and Delaware Geological Surveys and the Interstate Commission of the Potomac River Basin. The USGS publishes data for 137 streamflow stations and 379 observation wells across Maryland and Delaware.

The USGS serves the Nation by providing reliable scientific information to describe and understand the Earth; minimize loss of life and property from natural disasters; manage water, biological, energy, and mineral resources; and enhance and protect our quality of life.

** * USGS * * *

In-depth information about USGS programs may be found on the USGS home page at http://www.usgs.gov and http://chesapeake.usgs.gov/ for Chesapeake Bay activities.

Archived News Releases 2000-Present

2006

• 01-06-2006 Water Resources Plentiful at End of December 2005; Chesapeake Bay Flow Normal in 2005

2005

• 07-06-2005 Water Levels Fall as Summer Arrives
• 04-06-2005 March 2005 Water Levels Near Normal
• 03-04-2005 Flow Below Normal in Potomac River and Chesapeake Bay
• 02-07-2005 January 2005 Water Levels Normal to Above Normal
• 01-07-2005 2004 Ends with Normal to Above Normal Water Levels

2004

• 12-04-2004 Water Levels Remain Generally Above Normal
• 11-04-2004 Dry October Causes Water Levels to Drop
• 10-06-2004 Highest September Flow to the Chesapeake Bay Since 1937
• 09-03-2004 August Hurricanes Raise Water Levels in Southern Maryland
• 08-06-2004 Localized Flooding in Northeastern Maryland and Delaware in July
• 07-07-2004 Water Levels Normal to Above Normal in June
• 06-04-2004 Streams Return to Normal Levels in Maryland and Delaware during May 2004
• 05-06-2004 Streams Rise to Above Normal Levels in Maryland
• 04-07-2004 Streamflow and Groundwater Levels Fell in March 2004
• 03-04-2004 Streamflow and Groundwater Levels Normal to Above Normal in February 2004
• 02-04-2004 Cold, Dry January Leads to Drop in Water Levels
• 01-06-2004 Wettest Year Leads to Record-High Water Levels Including Third Highest Flow to Chesapeake Bay in December and 2003

2003

• 12-04-2003 More Record-High Water Levels in November 2003
• 11-04-2003 Record High Groundwater Levels in October 2003
• 10-03-2003 Flow to Chesapeake Bay in Water Year 2003 Second Highest Since 1937
• 09-05-2003 Third Consecutive Month of High Flow into the Chesapeake Bay
• 08-06-2003 Flow into Chesapeake Bay near Record High Levels
• 07-07-2003 Record Breaking High Water Levels in Maryland and Delaware
• 06-06-2003 Streamflow and Groundwater Levels High in May
• 05-07-2003 April Water Levels Normal
• 04-05-2003 Water Levels High in March - Water Restrictions Lifted
• 03-05-2003 Exceptionally Wet February Leads to High Water Levels
• 02-06-2003 Maryland and Delaware Streamflow and Groundwater Levels Remain Normal in January 2003
• 01-07-2003 2002: A Record-Setting Year for Low Groundwater Levels - Water Levels Recover to Normal in December 2002

2002

• 12-01-2002 Hydrologic Drought Wanes as Water Levels Rise
• 11-01-2002 Water Levels Rise Across Maryland and Delaware, But Drought Persists in Some Areas
• 10-03-2002 Water Levels Remain at Record-Setting Lows
• 09-05-2002 Groundwater in Parts of Maryland Reaches Lowest Levels Since 1962, Despite Late August Rains
• 08-06-2002 Drought Conditions Lead to 10 Record Low Monthly Groundwater Levels in July
• 07-03-2002 Record Low Water Levels Show the Effects of Long-Term Hydrologic Drought
• 06-04-2002 Groundwater Levels Reflect Long-Term Effects of Drought
• 05-02-2002 April Showers Not Enough to Raise Groundwater Levels
• 04-05-2002 The Drought in Full Bloom: Low Water Levels Result in Water Restrictions

2001

• 12-03-2001 Record Low Water Levels Set in November
• 11-02-2001 Dry October Leads to Low Water Levels
• 10-05-2001 Water Levels Low in Northern Maryland
• 09-07-2001 Water Levels Stable in August
• 08-06-2001 High and Low Water Levels in July
• 07-06-2001 Water Levels Continued to Improve in June
• 06-06-2001 Needed Rain Helps Avert a Drought in May
• 05-08-2001 Water Levels Still Normal in April, but More Rain is Needed
• 04-05-2001 Spring Rains Help Water Levels
• 03-06-2001 Water Levels Improve, But Are Still Below Normal
• 02-06-2001 Streamflow Still Low in Maryland in January
• 01-05-2001 Streamflow to Chesapeake Bay in 2000 Reflects Dry Autumn

2000

• 12-05-2000 Streamflow in Maryland Beginning to Show the Effects of Lack of Rain
• 11-07-2000 Despite Lack of Rain October Water Conditions near Normal
• 10-06-2000 September Water Conditions Above Normal in Maryland, Delaware, and D.C.
• 09-08-2000 August Water Conditions Above Normal in Maryland, Delaware, and D.C.
• 08-07-2000 July Water Conditions Continue Normal in Maryland, Delaware, and D.C.
• 07-07-2000 June Water Conditions Normal in Maryland, Delaware, and D.C.
• 06-06-2000 Water conditions begin to decline in Maryland, Delaware, and D.C.
• 05-05-2000 Water Conditions Continue to Improve in Maryland, Delaware, and D.C.
• 04-07-2000 Water Conditions Continue to Improve in Maryland, Delaware, and D.C.
• 03-07-2000 Water Conditions Improving in Maryland, Delaware, and D.C.
• 02-08-2000 January Streamflow and Ground Water Levels Still Low
• 01-06-2000 1999 Flow Into Chesapeake Bay Lowest Since 1960s Drought