Flow to Chesapeake Bay in Water Year 2003 Second Highest Since 1937

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: October 3, 2003

September 2003 was a month of excessively high rainfall and water levels throughout Maryland, Delaware, and Washington, D.C. Precipitation over the last 12 months has been far above normal levels, which has led to the highest September groundwater levels in 40 years, high streamflow levels and flooding, and near record-setting high flow into the Chesapeake Bay for the 2003 Water Year, according to hydrologists at the U.S. Geological Survey (USGS).

The water year (WY) is the natural, annual water cycle from October through September that is used by hydrologists. Streamflow and groundwater levels are generally at their lowest levels at the end of September and the recharge cycle begins again in October when water levels begin to rise because there is less demand for water from plants and people.

High Flows to the Chesapeake Bay

The mean monthly flow to the Chesapeake Bay for the 2003 water year (October 2002 through September 2003) averaged 76.2 bgd (billion gallons per day), which is the second highest level since record keeping began in 1937. The highest flow was during WY 1972 with 78.1 bgd. The average flow for a water year is 50.8 bgd. During WY 2002, the flow to the Bay was 28.6 bgd.

The graph below compares the mean monthly flow into the Bay during WY 2002 and WY 2003 to the long-term average level. The extreme lows to highs from one year to the next are unprecedented.

In WY 2002, the flow was below average every month except May and near-record low levels (based on 66 years of data) were set in August and September 2002. During WY 2003, 10 out of the 12 months were above average and flow in March, June, and September was especially high. Near record highs were set in June, July, August, and September. The flow to the Bay during September was about 4 times higher than average at 86.9 bgd, which was the third highest on record for September. The table below ranks the monthly flow values.

Month	2003	2002
June	Second Highest
July	Third Highest
August	Fourth Highest	Third Lowest
September	Third Highest	Fifth Lowest

Tropical Storm Isabel and Storm Surge

Tropical Storm Isabel engulfed the Mid-Atlantic on September 18 and 19, 2003 and brought a storm surge to the Chesapeake Bay that caused flooding on the shores of the Bay. The graph below shows the tidal water- level fluctuations and the storm-surge peak. The surge arrived at the mouth of Chesapeake Bay in Virginia at 6:24 PM (green line) and was rose to 6.12 feet above sea level. The storm surge took more than 18 hours to travel from the mouth of the Chesapeake Bay to the Baltimore area (blue line), where the water level reached its maximum of 7.36 feet. The storm surge not only affected the Bay, but went up into the tributaries that drain to the Bay, which are not usually influenced by tides. For example, Morgan Creek (red line) on the Eastern Shore of Maryland experienced tidal effects from the surge.

The above storm-surge arrival graph is based on data collected by the U.S. Geological Survey (Morgan Creek, USGS station 1492500) and the National Oceanic and Atmospheric Administration (Chesapeake Bay Bridge Tunnel, NOAA station 8638863 and Baltimore at Fort McHenry, NOAA station 8574680).

Impacts of High Flows to the Chesapeake Bay

High river flow during 2003 has contributed large amounts of nutrients and sediment to the Bay causing near-record low dissolved-oxygen levels and the water is less clear. The low dissolved-oxygen levels have caused fish kills in some Bay tributaries. The increased amount of nutrient and sediment have also clouded the waters in the Bay and likely will cause a decrease in the amount of submerged grasses in the Bay next year. The grasses may also be impacted by additional sediment from shoreline erosion during tropical storm Isabel. The full extent of underwater grasses lost will not be known until next year when surveys are conducted. The grasses had shown an increase from 1999-2002 due to smaller amounts of nutrients and sediment entering the Bay. This smaller amount of nutrients and sediment was attributed to both the drought and management actions. More information about streamflow, water quality, and the Chesapeake Bay can be found at http://chesapeake.usgs.gov/ and www.chesapeakebay.net.

Hydrologic Conditions in Maryland, Delaware, and Washington D.C.

Nearly twice the amount of normal rainfall fell in September. Rainfall at the Baltimore-Washington International (BWI) Airport from January to September 2003 was 14.96 inches above normal, and already exceeds the normal annual rainfall level (41.94 inches), according to the National Weather Service. Many months of above normal rainfall have led to above normal water levels and the ground is saturated. When it rains, the water has almost nowhere to go so it accumulates in depressions or becomes runoff, filling our waterways. The high water levels leave the region vulnerable to flooding. Above normal rainfall has left groundwater and streamflow levels across Maryland and Delaware at very high levels.

For news release and images, go to http://md.water.usgs.gov/publications/press_release/current/

The above map shows that at the end of September, all wells and streams measured by the USGS are at above normal levels (dark circles and triangles). Many of these streams and wells have been above normal for many months. Five wells are at their highest levels for September in 40 years (represented by an asterisk). Three streams had the highest monthly flow since record-keeping began.

Streamflow

Streamflow across Maryland and Delaware has been above normal for many months. Several rivers reached flood stage during September, including the Potomac and Monocacy Rivers. Monthly record highs were set in Maryland on the Youghiogheny River in Garrett County, and the Choptank River and Pocomoke River on Maryland's Eastern Shore, and White Clay Creek in New Castle County, Delaware. 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/.

The maps below show the status of real-time streamflow measurements before and after tropical storm Isabel (September 18) and the rainfall on September 22. The colors represent the percentile where the recent data fall in comparison to the historical record. Green is normal; blue and black are above normal. Black is a new daily high streamflow. Notice the change in streamflow ranking from before and after tropical storm Isabel and the September 22 rainfall. Current and historical streamflow data can be monitored on the web at http://waterdata.usgs.gov/nwis/rt.

Potomac River

The Potomac River Basin experienced 2 to 3 times the normal amount of rainfall in September, which resulted in 10 times the normal streamflow for September. The average monthly streamflow for September 2003 near the Potomac River near Washington, D.C. was 21.3 bgd, which is far above the normal streamflow of 2.2 bgd.

During WY 2003, average streamflow at the Potomac River near Washington, D.C. was the second highest since record-keeping began in 1930. The previous water year, WY 2002, had the lowest streamflow on record. Streamflow on the Potomac River at Paw Paw was the highest water year flow since 1938.

The Potomac River level exceeded flood stage (red line) during tropical storm Isabel and neared the flood stage with subsequent rainfall 4 days later. Streamflow has been above average every day since February 2003.

Groundwater

Groundwater levels are usually at their lowest levels near the end of September (end of the water year), yet the current water levels are at levels typically seen during spring. The water levels are elevated from the abundant rainfall this year. Groundwater levels in wells used by the USGS to monitor climatic conditions in the bi-state region were all at above normal levels, and wells in Anne Arundel, Baltimore, Charles, Harford, Prince George's, and Queen Anne's Counties, Maryland reached the highest September level in 40 years. Last September, nine wells had set new monthly low records and seven of these were all-time record lows.

The above hydrograph for a well in Baltimore County shows how the water level in the well, measured in depth below land surface, went from record-setting low levels in 2002 to record-setting highs only 1 year later. Recharge to this well has been remarkable. For 5-year hydrographs of groundwater levels for the climatic indicator wells, visit: http://md.water.usgs.gov/groundwater/.

Notice the groundwater response at this same well in Baltimore County to rainfall in the graph to the right. To monitor USGS real-time groundwater levels, visit the USGS NWISWeb site at: http://waterdata.usgs.gov/usa/nwis/rt.

Select groundwater from the data category, then real-time, then your region of interest, such as Maryland. The USGS has recently equipped wells in Frederick and Washington Counties in Maryland with real-time data collection.

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 near capacity in September.

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 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 region. The water resource data are published annually in two volumes (surface water and groundwater) and data for the 2002 Water Year is now available at http://md.water.usgs.gov under "publications".

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 on 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