Rainfall
associated with several hurricanes
in the Mid-Atlantic States resulted
in record high September streamflow
to the Chesapeake Bay, according to
hydrologists at the U.S. Geological
Survey (USGS). This is the highest
September flow to the Bay since record-keeping
began in 1937. High flows in September
continue a 3- month sequence of high
flows, which brings high amounts of
nutrients and sediment to the Bay.
The record flow caused scouring of
sediment from the Susquehanna River
at Conowingo Dam; the last time this
occurred was in 1996. Most of this
flow was from flooding in Pennsylvania,
where the upper part of the Chesapeake
Bay watershed is located (see more
details in the Chesapeake Bay section
below).
September
streamflow at the mouth of the Susquehanna
River was the highest monthly flow
in 67 years, with 113,800 cubic feet
per second (cfs). September flow was
72 percent higher than the previous
record (81,700 cfs), set in 1975.
The Susquehanna River typically contributes
half the flow to the Chesapeake Bay,
but during the last 3 months, the
contribution has been much higher.
The high flows brought higher than
usual amounts of sediment and nutrients.
The sediment is visible in the photo
at Conowingo Dam.
The
high flow and nutrient and sediment
loads in September will have some
short-term impact on conditions in
Chesapeake Bay in 2004 and may impact
conditions in spring 2005. Since the
high flows occurred late in the summer
of 2004, the impacts to the Bay may
be fairly small this year.
Streamflow
levels in central and western Maryland
were above normal, which includes
the Potomac River. In southern and
eastern Maryland and most of Delaware,
September water levels were normal,
except for northern Delaware, which
was above normal. An observation well
in Washington County, Maryland was
at its highest September level since
1996, which reflects the more than
7 inches of rain the region received.
Groundwater levels in other parts
of Maryland and Delaware were normal
to above normal; however, some wells
were measured before the hurricanes
crossed the region.
Precipitation
Rainfall
totals in September varied widely
across Maryland, Delaware, and Washington,
D.C. and were dependent on the paths
of hurricanes. Remnants of Hurricanes
Ivan and Jeanne brought more than
7 inches of rainfall to western Maryland
in September. Rainfall was also above
normal in northern Maryland and northern
Delaware. In Delaware, rainfall at
Wilmington was 9.31 inches, or 5.30
inches above normal, while rainfall
further south in Georgetown was 1.87
inches below normal, according to
preliminary rainfall data from the
National Weather Service. September
rainfall and temperatures were near
normal in Baltimore and Washington,
D.C., southern and eastern Maryland,
and southern Delaware. However, the
National Weather Service reported
that a record rainfall of 2.46 inches
was set on September 28 at Washington
National Airport, which broke the
old record of 1.69 set in 1907.
These
September storms, including Hurricane
Frances, dropped higher than normal
rainfall to the west and north of
Maryland, which caused major flooding
in western Maryland and along the
lower Susquehanna River. Rainfall
was also high in the Potomac River
Basin, leading to high flows on the
river and contributing to the highest
September flow to the Chesapeake Bay.
Status
of Streams and Wells
The
map to the left shows the location
of the wells and streams used by the
USGS to monitor water conditions in
Maryland, Delaware, and Washington,
D.C. Water levels were influenced
by the path of the hurricanes, which
crossed central and western Maryland.
The result was a new monthly high
for an observation well in Washington
County (see starred symbol on map),
and river levels rose to above normal
levels. In eastern Maryland, rainfall
was near normal, as were water levels
in this region.
Chesapeake
Bay
Monthly
mean streamflow into the Chesapeake
Bay during September averaged 116.2
bgd (billion gallons per day), which
is 430 percent above normal. This
is the highest September flow since
1937. Flow to the Bay has been in
the normal range since January, but
has been far above normal for the
last 2 months (see graphs below).
Flow
was normal until July 2004,
and has been above normal since
then because of several hurricanes.
See graph at http://md.water.usgs.gov/monthly/bay.html. |
This
graph shows how the September
2004 flow compares to normal
flow, and September flow in
2003 (also a high flow year),
and 2002 (a drought year). |
High
flow during the last 3 months has
contributed to the third highest water
year* flow (74.9 bgd) to the Bay.
Flow during the 2003 water year was
also high and ranked as the second
highest since record-keeping began.
Normal flow to the Bay is 50.5 bgd,
and flow during the dry water year
2003 was only 8.27 bgd.
|
*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. |
The
Susquehanna, Potomac, and James Rivers
are the largest rivers in the Chesapeake
Bay watershed and usually contribute
about 85 percent of the freshwater
streamflow to the Bay. In an average
year, approximately 50 percent of
the freshwater flow comes from the
Susquehanna River, 20 percent from
the Potomac River, and 15 percent
from the James River. The remaining
15 percent comes from surrounding
tributaries and smaller streams.
This
September, more freshwater entered
the Bay from the Susquehanna River
(63 percent) than normal, and the
flow at the mouth of the river was
the highest September flow on record.
While the Potomac and James Rivers
contributed proportionately less water
than normal, 14 percent and 9 percent
respectively, the Potomac River had
the fifth highest flow, and the James
River had the seventh highest flow.
The remaining 14 percent was from
other sources in September. More information
about USGS studies to help with the
protection and restoration of the
Chesapeake Bay and its watershed can
be found at http://chesapeake.usgs.gov.
According
to scientists, the increased nutrient
and sediment loads will probably only
have short-term impacts on the Bay
in 2004. The increased sediment will
result in less light in the Bay waters,
which could impact the growth of submerged
aquatic vegetation (SAV). However,
since it is late in the growing season
for SAV, this impact may be minimal.
SAV is important in the Bay because
it provides oxygen and habitat for
fish and crabs, and food for waterfowl.
The
increased nutrient loads could also
contribute to algal blooms which result
in low dissolved-oxygen levels in
the Bay, especially during the summer.
The low dissolved oxygen can cause
loss of fish, crabs, and oysters.
However, the higher nutrient loads
in September are occurring when Bay
waters are beginning to cool, so there
is less likelihood for impacts on
dissolved oxygen. The high nutrient
loads delivered this fall may cause
worse than normal algal blooms and
dissolved oxygen levels next spring
as the waters warm.
Streamflow
Streamflow
in Maryland and Delaware ranged from
normal to above normal in September.
Rainfall in western Maryland was twice
the normal amount for September, which
resulted in high flows and some new
daily record highs. Streams in the
central Maryland Piedmont region,
on the Eastern shore, and in most
of Delaware were flowing at normal
to above normal levels. Current and
historical streamflow data can be
monitored on the web at: http://waterdata.usgs.gov/.
Monthly streamflow has been at normal
to above normal levels since September
2002 at the Brandywine River in Delaware
and the following streams in Maryland:
Antietam Creek, Choptank River, Conococheague
Creek, Deer Creek, Monocacy River,
Patuxent River, Piscataway River,
Potomac River, Youghiogheny River,
and Winters Run. 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/.
Daily
streamflow on the Potomac River near
Washington, D.C. averaged 13.4 bgd
in September, which is 520 percent
above normal for the month of September.
Flow at the mouth of the Potomac River
entering the Chesapeake Bay during
September was the fifth highest on
record. Flow in 2003 was the second
highest. Streamflow on the Potomac
River during water year 2004 was 12.0
bgd, or 46 percent above normal. More
information on the Potomac River is
available at: http://md.water.usgs.gov/monthly/poto.html.
|
Streamflow,
also called discharge, approached
flood stage (shown as a green
line) three times in September
on the Potomac River near Washington,
D.C. Flow was normal (triangles)
at the beginning of September
and the three rises were related
to rainfall associated with
hurricanes in the Potomac River
Basin. Note that although the
river receded, it remained above
normal before the next rainfall
event and each peak was a little
higher than the previous. For
real-time streamflow and gage
height data, visit: http://waterdata.usgs.gov/. |
Groundwater-Unconfined
or Shallow Aquifers
Groundwater
levels were normal to above normal
during September in wells used by
the USGS to monitor unconfined or
shallow aquifer response to climatic
conditions in the Maryland, Delaware,
and Washington, D.C. region. Rainfall
associated with hurricanes caused
some groundwater levels to rise and
the observation well in Washington
County reached the highest September
level since 1996. For 5-year hydrographs
of groundwater levels for the climatic
indicator wells, visit: http://md.water.usgs.gov/groundwater/.
|
Groundwater
levels for this well in Frederick
County, Maryland show a response
to rainfall associated with
September hurricanes. Groundwater
levels are shown as depth below
land surface. A rise on the
hydrographs means that the groundwater
level is closer to land surface.
Note that the water level climbed
nearly 15 feet since the beginning
of September. For real-time
groundwater data, visit: http://waterdata.usgs.gov/. |
Groundwater-Confined
or Deep Aquifers
Water
levels in the deep confined aquifers
continue to decline because the wells
are pumped at higher rates than the
rate at which deep groundwater is
recharged. Because confined aquifers
are deep, water levels in confined
aquifers respond slowly to climatic
conditions. The network of confined
aquifer wells has been reduced because
of diminishing funds. Several wells
will no longer be measured on a monthly
basis, and the web pages will be updated
when data is collected. Limited data
for confined aquifer wells can be
viewed at: http://md.water.usgs.gov/groundwater.
Real-time water-level data can be
viewed at: http://waterdata.usgs.gov/md/nwis/gw
.
Reservoir
Storage
Storage
of the Baltimore reservoir system
rose 1 percent, to 97 percent of
capacity in September. The Baltimore
reservoirs (Loch Raven, Liberty,
and Prettyboy) have been nearly
full since May 2003. Storage in
the Triadelphia and Duckett Reservoirs
on the Patuxent River, which serve
Montgomery and Prince Georges Counties,
dropped 4 percent to 85 percent
of capacity in September.
Water
Monitoring
The
USGS has been collecting National
streamflow data for 120 years, since
1884. Streamflow monitoring began
in Maryland on the Potomac River
at Point of Rocks, Maryland in 1895
and continues today. Streamflow
and groundwater levels are used
to assess 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,
Delaware, and the District of Columbia,
visit Water Watch at: http://md.water.usgs.gov/waterwatch/.
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,
Baltimore City, and other agencies.
The long-term observation wells
used in this analysis are operated
in cooperation with the Maryland
and Delaware Geological Surveys
and the Interstate Commission on
the Potomac River Basin.
The
real-time wells are operated in
cooperation with the Maryland and
Delaware Geological Surveys, the
Interstate Commission on the Potomac
River Basin, and Calvert County,
Maryland. The USGS publishes data
for 137 streamflow stations, 393
observation wells, and 4 springs
across Delaware, Maryland, and the
District of Columbia.
The
USGS, a Bureau within the Department
of the Interior, has served the
Nation and the world for 125 years
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; to make important
decisions and enhance and protect
our quality of life.
Recently
Released USGS Report: Streamflow statistics
for 15 streams in Delaware
A
new Open-File Report that contains
low-flow statistics for 15 streamgaging
stations in Delaware has been released
by the Maryland-Delaware-District
of Columbia District of the U.S. Geological
Survey. The statistics contained in
the report, OFR 2004-1313, can be
used by engineers, planners, land
and water-resource managers, biologists,
and many others to help in the design
and management of water-related infrastructure
and protection of habitat for aquatic
plants and animals. The report, written
by hydrologist Kernell Ries, contains
low-flow frequency statistics, such
as the 7-day, 10-year low flow, and
flow-duration statistics, such as
the 95-percent duration flow. The
average flow over a 7-day period is
less than the 7-day, 10-year flow,
on average, once in 10 years. The
95-percent duration flow is the flow
that is equaled or exceeded 95 percent
of the time. In addition to these
flow statistics, the report contains
several other low-flow frequency and
flow-duration statistics. The report
is available online only at http://md.water.usgs.gov/publications/ofr-2004-1313/.
*
* * 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 |
<
< |
2004
- 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
|