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Summary of May 2009 Monthly Hydrologic Conditions

Compiled in cooperation with the New Jersey Department of Environmental Protection
Provisional assessment of hydrologic conditions in New Jersey

May 2009

Precipitation was below normal at the Newark index station, and above normal at the Atlantic City and Trenton index stations. Newark reported 4.08 inches, which is 91.5 percent of normal.  Atlantic City reported 3.43 inches, which is 101.48 percent of normal.  Trenton reported 5.19 inches, which is 138 percent of normal. Total precipitation over the past 12 months was: 44.2 inches at Newark, which is 2.06 inches below normal; 43.8 inches at Atlantic City, which is 3.23 inches above normal; and 40.51 inches at Trenton, which is 0.88 inches below normal.

Combined storage in the thirteen major water supply reservoirs as of May 31 was 74.883 billion gallons (93.1 percent of capacity), which is higher than the average May contents for the reference period 1961-1990.  The storage was 2.399 billion gallons more than one month ago and 2.621 billion gallons less than one year ago.  The thirteen major water supply reservoirs are as follows: Lake Tappan, Woodcliff Lake, Oradell Reservoir, DeForest Lake, Splitrock Reservoir, Boonton Reservoir, Canistear Reservoir, Oak Ridge Reservoir, Clinton Reservoir, Charlottesburg Reservoir, Echo Lake, Wanaque Reservoir and Spruce Run Reservoir.                

Streamflow was below normal at all three index stations. The monthly-mean discharge at South Branch Raritan River near High Bridge was 103 ft3/s, 60.2 percent of normal.  The monthly-mean discharge of the Great Egg Harbor River at Folsom was 90.6 ft3/s, 88.8 percent of normal.  The monthly mean discharge of the Delaware River at Trenton was 12210 ft3/s, 79.2 percent of normal. The observed daily mean discharge of the Delaware River at Trenton on May 31 was 18100 ft3/s.

Groundwater levels, as measured in water-table observation wells for the month of May, were above normal at the Readington School 11 and the Morrell 1 index wells, but below normal at the Vocational School 2 index well. Levels decreased from last month, and were lower than one year ago at the Morrell 1 and Vocational School 2 index wells.  Levels increased from last month, and were higher than one year ago at the Readington School 11 index well.

Water quality parameters collected from the Delaware River at Trenton were within recorded historical monthly extremes. Water temperature ranged from 22.1 to 14.6 degrees Celsius. Dissolved oxygen ranged from 11.5 to 8.3 milligrams per liter. Specific conductance ranged from 248 to 124 microsiemens per centimeter at 25°C.

All of the files listed below are in Portable Document Format (PDF) which can be viewed/printed with the Adobe Acrobat® Reader, freely available for most computer platforms.

• Combined Storage in the 13 Major Water Supply Reservoirs
• Monthly precipitation at three selected sites
• Groundwater levels in selected Water-table observation wells
• Streamflow at selected sites
• Water quality for the Delaware River at Trenton