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Summary of April 2007 Monthly Hydrologic Conditions

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

April 2007

Precipitation was above normal at all three index stations, with new April period-of-record maximums occurring in Newark and Trenton. Newark reported 11.85 inches, which is 302 percent of normal. The Newark monthly total is 0.71 inches greater than the previous record from 1983. Trenton reported 9.96 inches, which is 277 percent of normal. The Trenton monthly total is 0.36 inches greater than the previous record from 1983. Atlantic City reported 5.47 inches, which is 156 percent of normal. Total precipitation over the past 12 months was: 58.85 inches at Newark, which is 12.60 inches above normal; 56.13 inches at Trenton, which is 14.74 inches above normal; and, 53.56 inches at Atlantic City, which is 12.97 inches above normal.

The majority of the total April precipitation was the result of a late spring nor’easter which occurred on April 15-16. The widespread heavy rain produced flooding throughout the state. More information about the flooding can be obtained at the USGS at the following URL: http://nj.usgs.gov/special/flood0407/

Combined storage in the thirteen major water supply reservoirs as of April 30 was 79.8 billion gallons (99.2 percent of capacity), which is greater than the average April contents for the reference period 1961-1990. The storage was 3.00 billion gallons more than one month ago and 3.42 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, Charlottesburg Reservoir, Echo Lake, Wanaque Reservoir and Spruce Run Reservoir.

Streamflow was above normal at all three index stations. The monthly-mean discharge at South Branch Raritan River near High Bridge was 363 ft³/s, 173 percent of normal. The monthly-mean discharge of the Great Egg Harbor River at Folsom was 213 ft³/s, 176 percent of normal. A daily mean flow of 917 ft³/s on April 17 at Folsom set a new April period-of-record maximum. The monthly mean discharge of the Delaware River at Trenton was 35,000 ft³/s, 162 percent of normal. The observed daily mean discharge of the Delaware River at Trenton on April 30 was 20,000 ft³/s.

Groundwater levels, as measured in water-table observation wells for the month of April, were above normal at all three index wells. Levels increased from last month, and were higher than one year ago at all three index wells.

Water quality parameters collected from the Delaware River at Trenton were within recorded historical monthly extremes. Water temperature ranged from 5.0 to 14.2 degrees Celsius. Dissolved oxygen ranged from 9.8 to 13.8 milligrams per liter. Specific conductance ranged from 90 to 173 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