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Most Recent Hydrologic Conditions Report
December 7, 2015
Precipitation

The observed precipitation for the Delaware River Basin above Montague, New Jersey for the period January 1, 2015 through December 6, 2015 was 40.36 inches, or 2.20 inches below normal. For the same period, the observed precipitation for the Delaware River Basin above Trenton, New Jersey was 40.76 inches, or 4.20 inches below normal. Also through December 6, the observed precipitation for Wilmington, Delaware was 44.79 inches, or 4.52 inches above normal.

The attached table summarizes precipitation for 2014 and 2015 for select stations in the Delaware River Basin.

Precipitation Departure Maps (National Weather Service Middle Atlantic River Forecast Center's Web Site)

Streamflow

The average observed streamflow of the Delaware River at Montague, New Jersey in November 2015 was 4,393 cubic feet per second (cfs), or 97-percent of the long-term average for the month. The average observed streamflow of the Delaware River at Trenton, New Jersey in November was 8,351 cfs, or 83-percent of the long-term average for the month.

During December 1-6, the average observed streamflow of the Delaware River at Montague was 4,883 cfs, or 97-percent of the long-term average for the month.  Similarly, the average streamflow at Trenton was 9,202 cfs, or 71-percent of the long-term average for the month.

Below are graphical presentations of daily mean streamflows at Montague and Trenton for the 365-day period ending December 6, 2015.

Reservoirs

Lower Basin

Lower Basin Reservoir Storage as of December 7, 2015:
Beltzville

13.54 billion gallons (bg) usable, or 100% of usable storage

Blue Marsh

4.50 bg usable, or 102% of winter pool usable storage

Merrill Creek

14.05 bg usable, or 90% of usable storage (as of November 30)

Upper Basin

New York City (NYC) Delaware Basin Reservoir Storage as of December 7, 2015:
Pepacton

98.5 bg usable, or 70.3% of usable storage

Cannonsville

64.5 bg usable, or 67.4% of usable storage

Neversink

33.0 bg usable, or 94.4% of usable storage

Total

196 bg usable, or 72.4% of usable storage

The long-term median storage for the NYC Delaware basin reservoirs for December 7 is 203.8 bg, or 75.3% percent of usable storage.

Attached is a graphical presentation of the reservoir storage levels from January 2014 to the present.

Groundwater

The table below displays the current status (December 7, 2015) of groundwater levels for 14 monitoring wells in the Delaware River Basin and compares them to levels reported at the last DRBC commission meeting. Refer to Groundwater Notes at the end of this report for more details about the wells. Water levels within the 25- to 75- percentile range are defined as “normal”.

COUNTY

STATE

AGENCY
DATA

WELL ID

YEAR RECORD BEGINS

INDICATOR STATUS AS OF SEPTEMBER 15, 2015

CURRENT INDICATOR STATUS AS OF
DECEMBER 7, 2015

Sullivan

NY

USGS

Sv 535

2001

Normal

Normal

Wayne

PA

USGS

WN 64

1967

Normal

Normal

Monroe

PA

USGS

MO 190

1967

Normal

Drought Watch

Carbon

PA

USGS

CB 104

1969

Above Normal

Normal

Schuylkill

PA

USGS

SC 296

1975

Normal

Normal

Lehigh

PA

USGS

LE 644

1971

Normal

Normal

Berks

PA

USGS

BE 623

1975

Drought Warning

Below Drought Emergency

Lebanon

PA

USGS

LB 372

1973

Normal

Normal

Bucks

PA

USGS

BK 1020

1975

Normal

Normal

Chester

PA

USGS

CH 10

1966

Normal

Drought Watch

Delaware

PA

USGS

DE 723

1983

Drought Watch

Drought Watch

Burlington

NJ

USGS

050689

1955

Normal

Below Normal

Cumberland

NJ

USGS

110042

1972

Above Normal

Normal

New Castle

DE

Delaware GS

Db24-18

1993

Normal (August 13, 2015)

Normal

Chlorides (Salt Front)

The salt front is defined as the 250 parts-per-million isochlor. The seven-day average location of the salt front is used by DRBC as an indicator of salinity intrusion in the Delaware Estuary. The salt front's location fluctuates along the main stem Delaware River as streamflow increases or decreases in response to changing inflows, diluting or concentrating chlorides in the river.

During November, the location of the seven-day average of the 250-ppm isochlor (salt front) ranged from river mile 80 at the start of the month to river mile 73 by November 30. The normal location of the salt front during November is river mile 70, a location which is eight miles downstream of the Delaware-Pennsylvania state line.

As of December 6 (the most recent date for available data), the salt front was estimated to be located at river mile 73, which is four miles upstream of the normal location of the salt front during December.

Prepared by DRBC Staff.
Acknowledgments: Kimberly-Clark Corp.; National Weather Service; New York City Department of Environmental Protection; U.S. Army Corps of Engineers; U.S. Geological Survey; and Delaware Geological Survey.

Groundwater Notes:

  • Counties are ordered from North to South and East to West
  • Indicator status for PA wells is based on 30-day moving average of daily measurements and 30-day moving average statistics.
  • Indicator status for NY and NJ wells is based on a daily measurement and monthly-averaged statistics.
  • Indicator status for the DE well is based on a monthly, instantaneous measurement and monthly-averaged statistics.
  • The historical record for the NY well is too short to define a “normal” zone.  A graph of daily water levels is available on-line.
  • Records of groundwater levels (depth to water) at each well can be statistically analyzed to determine the percent of time that a given value is not exceeded. For example, the 25-percentile groundwater level is the level that is not exceeded 25 percent of the time in the existing record. Such percentiles are useful to compare to current groundwater levels; the three most commonly reported are the 25-, 50- and 75-percentiles (the 50-percentile is also called the median value). In this report we follow the customary practice of referring to the range of values defined by the 25- and 75-percentile as the “normal” range.
  • USGS uses the following definitions for water-level statistics: Normal (25- to 75- percentile flows); Drought Watch (10- to 25- percentile flows); Drought Warning (5- to 10- percentile flows); and Drought Emergency (0- to 5- percentile flows). Note: The categories labeled Drought Watch, Drought Warning, and Drought Emergency reflect only the relative range of the indicator values and are used for hydrological assessment purposes. Such category labels areindependent of official drought status which is declared only by the Governor of the respective state. Official declarations of drought stage are based upon a review of multiple ground and surface water conditions, soil moisture, precipitation, weather forecasts, purveyor reports, and other considerations.