December 2007 USGS Maryland-Delaware-DC Water Conditions Summary
Compiled by Wendy S. McPherson, Hydrologist
Above normal rainfall throughout Maryland, Delaware, and the District of Columbia in December caused many streamflow levels and some ground-water levels in stations monitored by the U.S. Geological Survey (USGS) to rise, and many reached the normal range. Water levels typically rise this time of year because of reduced water demands from vegetation and cooler temperatures leading to less evaporation. Ground water usually is recharged from late fall to spring, and helps to maintain streamflows during the typically dry period of late summer. Of the 28 climatic indicator wells used to measure ground water levels, 54% remain below normal in December, and record lows were set at two wells.
The recent rains helped streamflow levels rise, especially in western Maryland. Streamflow approached a record December high on the Youghiogheny and Savage Rivers in Garrett County. These streams are shown as blue triangle on the map below.
In contrast, the southern part of the Delmarva Peninsula did not receive as much rain. Notice the red and brown triangle and circle symbols on the map above indicating record lows and near-record lows. The Nassawango Creek near Snow Hill in Worcester County set a new record low for December, breaking the record set in 1965. According to hydrologists at the USGS, more rain or snow is needed in central and eastern Maryland to prevent low water levels next summer.
Precipitation
Rainfall in December was above normal at the National Weather Service stations in Maryland and Delaware. The Georgetown, Delaware weather station registered 1.42 inches above normal for a total of 4.82 inches. (source: National Weather Service).
Despite the above normal rainfall in December, annual rainfall deficits still exist in all but one county across Maryland, Delaware, and the District of Columbia. Garrett County, Maryland is the only exception that had no deficit. Based on preliminary data from the National Weather Service, the following counties have a deficit of more than 10 inches: Sussex County in Delaware, and Caroline, Dorchester, Howard, Montgomery, Somerset, and Wicomico Counties in Maryland.
Streamflow
Streamflow at gages used by the USGS as climate indicators across the Maryland, Delaware, District of Columbia region ranged from above normal at 10% of stations to below normal at 30% of stations, leaving the remainder in the normal range.
Streamflow on the Nassawango Creek near Snow Hill in Worcester County set a new record low for the second consecutive month. The streamflow in December exceeded the record set during the drought in 1965. The USGS has been collecting streamflow data on the Nassawango since 1949. The Nanticoke River in Sussex County, Pocomoke River in Worcester County, and St. Clements Creek in St. Mary's County also had very low streamflows in December.
The graph below shows monthly streamflow for Nassawango Creek. The yellow triangles represent the 2007 monthly mean flows. The cyan color represents normal streamflow. The vertical bars indicate the historic monthly low streamflow level, including the year, which are shown in red where new record monthly low streamflow levels have been reached. Record lows have been set on the Nassawango Creek in September, November, and December 2007.
The 5-year hydrograph shows that the Nassawango Creek streamflow level has been below normal since May 2007. The water level has risen, but remains at record setting low levels.
Streamflows in western Maryland were exceptionally high and streamflow on the Youghiogheny and Savage Rivers in Garrett County approached record December highs. This hydrograph for the Youghiogheny River shows the steep climb in streamflow level in December. Wills Creek in Allegany County was also above normal.
Ground Water
The 5-year hydrograph for the unconfined well in Wicomico County shows that the water level is at record lows in September, October, and December. Water levels have been collected at this well for 58 years.
The water level in the Charles County well showed significant recovery over the last two months, but still remains much below normal.
Chesapeake Bay Freshwater Flow
The estimated mean monthly flow to the Chesapeake Bay for December was 83,800 cfs (cubic feet per second) or about 101 percent of the long-term mean for December. Average December flow is 83,200 cfs.
Reservoirs
Water available from the Baltimore reservoir system (Loch Raven, Liberty, and Prettyboy) was 51.6 billion gallons or 68% of the available storage at the end of December. Water stored in the Triadelphia and Duckett Reservoirs, which serve Montgomery and Prince George's Counties, was at 58% of the normal capacity at the end of December.
| November 2007 | Percent available | Volume (billion gallons) | Source |
|---|---|---|---|
| Baltimore Reservoirs | Baltimore City | ||
| Loch Raven | 79% | 16.3 | |
| Liberty | 74% | 25.6 | |
| Prettyboy | 58% | 9.6 | |
| Total | 68% | 51.6 | Increased 2% since November |
| Patuxent Reservoirs | WSSC | ||
| Tridelphia | 71% | 3.99 | |
| Duckett | 44% | 2.18 | |
| Total | 58% | 6.17 | Increased 5% since November |
More Information
- Maryland-Delaware-District of Columbia
- USGS Drought Watch
- USGS Water Summary
- Streamflow
- Ground Water
- Chesapeake Bay
- National
- USGS Streamflow and ground-water levels
- U.S. Drought Monitor from the National Drought Mitigation Center
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
