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Summary of April 2012 Monthly Hydrologic Conditions

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

April 2012

Precipitation was below normal at all three index stations for the reference period 1981-2010. Newark reported 3.45 inches, which is ­­­­82.14 percent of normal.  Atlantic City reported 2.93 inches, which is 80.72 percent of normal.  Trenton reported 2.61 inches, which is 73.73 percent of normal. Total precipitation over the past 12 months was: 59.04 inches at Newark, which is 12.79 inches above normal; 44.10 inches at Atlantic City, which is 2.35 inches above normal; and 52.64 inches at Trenton, which is 6.20 inches above normal.

Combined storage in the thirteen major water supply reservoirs as of April 30 was 72.677 billion gallons (89.9 percent of capacity), which is higher than the average April contents for the reference period 1961-1990.  The storage was -0.780 billion gallons less than one month ago and -7.159 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, Charlotteburg Reservoir, Echo Lake, Wanaque Reservoir and Spruce Run Reservoir.

Streamflow was below the long-term monthly-mean for the reference period 1981-2010 at all three index stations. The monthly-mean discharge at South Branch Raritan River near High Bridge was 85.8 ft³/s, 42.5 percent of the long-term mean. The lowest Daily mean flow for the period of record for April was observed on April 18, 20, and 21, of 46 ft³/s.  The monthly-mean discharge of the Great Egg Harbor River at Folsom was 75.5 ft³/s, 62.9 percent of the long-term mean.  The monthly mean discharge of the Delaware River at Trenton was 6,634 ft³/s, 31.3 percent of the long-term mean. The lowest daily mean flow of 3,480 ft³/s for the period of record for the month of April was observed on April 21. The observed daily mean discharge of the Delaware River at Trenton on April 30 was 8,000 ft³/s.

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

Water-quality parameters collected from the Delaware River at Trenton were within recorded historical monthly extremes. Water temperature ranged from 9.6 to 20.2 degrees Celsius. Dissolved oxygen ranged from 8.0 to 17.1 milligrams per liter. Specific conductance ranged from 146 to 254 microsiemens per centimeter at 25°C.

Note: The preceding data is preliminary and subject to revision.

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