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Summary of May 2015 Monthly Hydrologic Conditions

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

May 2015

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

Precipitation was above normal at the Newark index station and below normal for the Trenton and Atlantic City index Stations for the reference period 1981-2010. Newark reported 4.93 inches, which is 120.54 percent of normal.  Atlantic City reported 0.71 inches, which is 21.19 percent of normal.  Trenton reported 0.63 inches, which is 14.42 percent of normal. Total precipitation over the past 12 months was: 43.69 inches at Newark, which is 2.56 inches below normal; 52.14 inches at Atlantic City, which is 10.39 inches above normal; and 37.72 inches at Trenton, which is 8.72 inches below normal.

Combined storage in the thirteen major water supply reservoirs as of May 31 was 71.672 billion gallons (88.6 percent of capacity), which is less than the average May contents for the reference period 1961-1990.  The storage was 3.749 billion gallons less than one month ago and 5.976 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 66.7 ft3/s, 43.6 percent of the long-term mean.  The monthly-mean discharge of the Great Egg Harbor River at Folsom was 59.5 ft3/s, 64.1 percent of the long-term mean.  The monthly mean discharge of the Delaware River at Trenton was 5,555 ft3/s, 40.2 percent of the long-term mean. The observed daily mean discharge of the Delaware River at Trenton on May 31 was 4,530 ft3/s.

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

Water-quality parameters collected from the Delaware River at Trenton exceeded the maximum range of historical monthly values for Specific Conductance. Water temperature ranged from 14.9 to 26.9 degrees Celsius. Dissolved oxygen ranged from 7.8 to 11.8 milligrams per liter. Specific conductance ranged from 208 to 285 microsiemens per centimeter at 25°C. Specific Conductance reached a new record high for the month of May.

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

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