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Picture of a USGS scientist making a streamflow measurement


Summary of July 2011 Monthly Hydrologic Conditions

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

July 2011

Map of New Jersey showing sites where hydrologic conditions are reported.

Precipitation was below normal at the Newark and Trenton index gages, and above normal at the Atlantic City index gage. Newark reported 2.04 inches, which is 44 percent of normal.  Trenton reported 1.92 inches, which is 45 percent of normal.  Atlantic City reported 4.15 inches, which is 108 percent of normal. Total precipitation over the past 12 months was: 44.72 inches at Newark, which is 1.53 inches below normal; 40.26 inches at Trenton, which is 1.13 inches below normal; and 38.01 inches at Atlantic City, which is 2.58 inches below normal.

Combined storage in the thirteen major water supply reservoirs as of July 31 was 71.97 billion gallons (89 percent of capacity), which is greater than the average July contents for the reference period 1961-1990.  The storage was 7.09 billion gallons less than one month ago and 11.88 billion gallons more 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 1971-2000 at the High Bridge index station, and above normal at the Folsom and Trenton index gages. The monthly-mean discharge at South Branch Raritan River near High Bridge was 59.9 ft3/s, 65 percent of the long-term mean.  The monthly-mean discharge of the Great Egg Harbor River at Folsom was 70.9 ft3/s, 108 percent of the long-term mean.  The monthly mean discharge of the Delaware River at Trenton was 10,730 ft3/s, 147 percent of the long-term mean. The observed daily mean discharge of the Delaware River at Trenton on July31 was 6,080 ft3/s.

Groundwater levels, as measured in water-table observation wells for the month of July, were below normal and decreased from last month at all three index wells. Compared to one year ago, levels were higher at the Readington School 11 well, but lower at the Morrell 1 and Vocational School 2 wells.

Water-quality parameters collected from the Delaware River at Trenton were within recorded historical monthly extremes. Water temperature ranged from 21.4 to 31.6 degrees Celsius. Dissolved oxygen ranged from 6.2 to 11.5 milligrams per liter. Specific conductance ranged from 107 to 228 microsiemens per centimeter at 25°C.

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

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