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Summary of Annual Hydrologic Conditions - 1998
Volume 1: Water-Quality
Below normal streamflow during October to December and August to September at three index stations-South Branch Raritan River near High Bridge, Great Egg Harbor River at Folsom, and Delaware River at Trenton (fig. 1)-resulted, generally, in high concentrations of the sum of dissolved solids. These concentrations were determined to be in the 50th- to 95th-percentile range of the dissolved solids concentrations measured at South Branch Raritan River at South Branch, Great Egg Harbor River at Weymouth, and Delaware River at Trenton. The sum of dissolved constituents, or dissolved solids (DS), is an approximation of the measurement commonly referred to as total dissolved solids. Normal and above normal streamflow during February to June resulted in generally normal and below normal concentrations of DS, which were determined to be in the 25th- to 50th-percentile range of DS concentrations. Low streamflows result in decreased dilution and, in turn, increased concentrations of DS. High streamflows result in increased dilution and, in turn, decreased concentrations of DS. A decrease in concentrations of DS generally indicates an improvement in overall water quality because concentrations of undesirable substances, such as trace metals, nutrients, organic compounds, bacteria, and nuisance aquatic organisms, typically decrease as well. The degree of dilution is apparent when monthly mean values of specific conductance (SC), which is directly related to DS concentration, for water year 1998 are compared with mean SC values from an earlier period. Monthly mean SC values for 1998 from the continuous monitoring station on the Delaware River at Trenton, which monitors a large drainage area in west-central New Jersey and parts of New York and Pennsylvania, are shown in relation to mean monthly SC values for 1968-97 in figure 2. Monthly mean SC values were less than long-term mean monthly values during the period of above normal streamflow, January to July. Monthly mean SC values were greater than long-term mean monthly values during the periods of below normal streamflow, October to December and August to September. All monthly mean SC values during water year 1998 were within the range of historical maximum and minimum monthly mean values (1968-97).
The monthly mean water temperature values from the continuous monitoring station on the Delaware River at Trenton during water year 1998 were within the range of historical maximum and minimum monthly mean values (1968-97), except during January and February (fig.3). The mean for January 1998 of 3.5 C and the mean for February 1998 of 4.5 C exceeded the historical maximum monthly mean values of 3.4 C and 3.9 C, respectively. According to the Northeast Regional Climate Center of Cornell University in Climate Impacts- January and February 1998, New Jersey had its third-warmest January and warmest February on record (1895-1997), with statewide monthly average air temperatures that were 5.8 C and 4.3 C warmer than the January and February long-term average air temperatures, respectively.
Dissolved oxygen (DO) concentration generally exhibits an immediate inverse relation to water temperature. As water temperature decreases, oxygen concentration increases; as water temperature increases, oxygen concentration decreases. DO varies seasonally in all surface-water bodies in New Jersey, with yearly maximums occurring in winter and yearly minimums occurring in summer. DO extremes (daily, monthly, or yearly) do not necessarily occur at the same time as water-temperature extremes. Photosynthesis is the primary variable affecting the DO-temperature relation; water clarity, and strength and duration of sunlight, in turn, affect photosynthesis. The monthly medians of daily maximum and minimum DO concentrations from the continuous monitoring station on the Delaware River at Trenton during the 1998 water year were within the range of historical (1968-97) extreme monthly-median values (fig. 4). The highest monthly median of the daily maximum DO concentrations (13.9 mg/L) occurred in December along with the year's lowest monthly mean water temperature of 3.4C. The lowest monthly median of the daily minimum DO concentrations (8.1 mg/L) occurred in June probably as a result of microbiological respiration because the year's highest monthly mean water temperature of 26.2C occurred in August.
Presence of Water-Column Nutrients, Common Ions, Trace Elements, and Organic Compounds in New Jersey Streams
The analysis for water-phase concentrations of total and filtered nutrients, dissolved common ions, and biochemical oxygen demand (BOD) in many New Jersey streams, and whole-water-recoverable (WWR) trace elements in a limited number of streams, has been ongoing as part of the U.S. Geological Survey (USGS)-N.J. Department of Environmental Protection (NJDEP) cooperative Ambient Stream Monitoring Program (ASMP) since 1973. In 1976 the number of stations on streams sampled for WWR trace elements was increased to about 60 percent of the total number of stations. The ASMP network was redesigned for the 1998 water year (published in this report); the percentage of stations sampled for WWR trace elements was reduced to about 40 percent of the 115 stations sampled; and, for the first time, water samples were analyzed for volatile organic compounds (VOCs) and filtered organic pesticides. Refer to Water Quality Stations in Downstream Order in the table of contents for the page on which water-quality records for a particular station are listed. Stations are designated with a "w" if samples were collected for WWR trace-element analysis, with a "v" if samples were collected for VOC analysis, and with a "p" if samples were collected for organic pesticide analysis. Samples for the analysis of VOCs, organic pesticides, and trace elements were collected once a year at statewide-status and background stations. Samples for VOC analysis were collected and analyzed during the February-March sampling period, for pesticide analysis during the May-June period, and for WWR trace-element analysis during the August-September period. Water-column samples for the analysis of nutrients, common ions, and BOD were collected four times a year at all stations in the network. Refer to Special Networks and Programs in the introduction for a description of the ASMP and definitions of statewide-status, background, and other station descriptors.
Summary statistics for measured constituent concentrations in water-column samples collected during water year 1998 are presented in figure 5 as a function of land use and include statistics for total nitrogen, filtered nitrite-plus-nitrate, total phosphorus, sum of dissolved constituents or DS, and BOD. Values reported by the analyzing laboratory as less than the minimum reporting level are included in each summary, but are reported as a value equal to one-half the minimum reporting level (MLR) or, for constituents with multiple MLRs, as one-half the largest MRL. Statistical data presented are from 4 sampling events at 95 stations. Twenty-eight stations were assigned a predominant land use designation of agricultural; 35, forest; 26, urban; and 6, background. Land-use designations at ASMP sample collection stations were determined by using digital data (scale 1:24,000, 1986) from the geographic information system of the NJDEP. Some stations, as a part of other networks, were sampled more than four times. Concentrations of total nitrogen and DS were calculated and, therefore, have fewer values than other constituents because, if one or more required components were missing, the calculation was not made. Median concentrations of the nutrient species of total nitrogen, filtered nitrite-plus-nitrate, and total phosphorus, in general, were greater in samples from stations in agricultural and urban land-use areas than in those from forest or background areas. For the nutrient species, the lowest median concentrations generally were present in samples from stations in background areas. For DS and BOD, median concentrations were greater in samples from stations in urban and agricultural land-use areas than in samples from stations in forest or background areas.
Summary statistics of the distribution and frequency of detection of measured concentrations of WWR trace elements, VOCs, and organic pesticides, as a function of land use, are presented in figures 6, 7, and 8. Only detected compounds found in one or more samples are presented. A detected compound is one whose value is reported to be greater than or equal to the laboratory's minimum reporting level (MRL) or non-detect value (NDV). Also included in the summary statistics are estimated values (marked with "E" in the data tables) reported by the laboratory to be greater than the long-term method detection level but less than the MRL or NDV. Refer to Laboratory Measurements in the Introduction for additional information about estimated concentrations. Figure 6 presents the concentration and frequency of selected trace elements (arsenic, chromium, copper, lead, nickel, and zinc) detected in samples from 36 stations in the ASMP. See individual station records for the complete list of trace elements included in the analysis. Boron, iron, and manganese are excluded from figure 6 because they were commonly found in natural waters. Barium, beryllium, cadmium, mercury, silver, and selenium are also excluded from figure 6 because all but barium were not detected in any sample; barium was detected in only two samples. Arsenic, copper, lead, and zinc were most frequently detected in samples from urban land-use areas. The highest concentrations of copper, lead, and zinc were detected in samples from urban areas. Chromium and nickel were most frequently detected, and had the highest concentrations, in samples from forest land-use areas.
The distribution and frequency of 7 of the 29 target VOC analytes detected in samples from 37 stations in the ASMP are shown in figure 7. See individual station records for the complete list of VOCs included in the analysis. Chloroform was detected twice in samples from stations in background land-use areas, but the highest concentration was present in a sample from an urban area. Chloroform was the only VOC detected in samples from stations in background land-use areas. A common source of chloroform is the chlorination of drinking water, which produces chloroform as a by-product. Methyl tert-butyl ether (MTBE) was most frequently detected, and was present in the highest concentrations, in samples from stations in urban land-use areas. MBTE is a fuel oxygenate added to gasoline for more than a decade to enhance fuel octane. Tetrachloroethylene was detected in samples from stations in three of four land-use areas, but was present in the highest concentration in a sample from an urban area. Tetrachloroethylene is a chlorinated solvent commonly used as a degreaser. 1,2-dichlorobenzene, 1,4-dichlorobenzene, and toluene were detected only in samples from stations in forest land-use areas. Dichlorobenzene compounds are used as insecticidal fumigants. Trichloroethylene, a commonly used degreaser also found in dyes, inks, cleaners, and disinfectants, was detected only in samples from stations in urban land-use areas.
The distribution and frequency of 14 of the 48 target filtered organic pesticides detected in samples from 36 stations in the ASMP are presented in figure 8. Refer to Laboratory Measurements in the Introduction for a complete list of pesticide compounds included in analysis Schedule 2001. Greater frequencies of detection and higher concentrations of pesticides were present about equally in samples from stations in agricultural and urban land-use areas. Only four compounds, detected in low levels, were found in samples from stations in background land-use areas.
In water year 1998, the USGS and the NJDEP, as part of the cooperative Ambient Ground-Water-Quality Monitoring Network, assessed the quality of ground water in the southwestern part of the Newark Basin (Piedmont Physiographic Province). Twenty-two domestic supply wells, selected to provide uniform coverage of the study area, are located in parts of Hunterdon, Mercer, and Somerset Counties, and in parts of NJDEP Watershed Management Areas 6, 8, 9, 10, and 11 (figs. 9 and 14; table 1 [in pdf format]).
This assessment consisted of chemical analyses of ground-water samples collected from wells that were sources of drinking water. All wells, except one with a polyvinyl-chloride casing, have steel casings ranging from 22 to 100 feet in depth, are open to fractured rock, and were drilled sometime within the last 10 years. The depths of the wells range from 125 to 250 feet. Fifteen of the wells have water-yielding open intervals in the Passaic Formation, aquifer unit or hydrogeologic code 227PSSC. Three have open intervals in the Lockatong Formation, hydrogeologic code 231LCKG. Three have open intervals in the Preakness Basalt, hydrogeologic code 227PRKS. One has an open interval in diabase, hydrogeologic code 227DIBS. (Diabase is a dark-grey to black, fine-textured, igneous rock consisting mainly of feldspar and pyroxene. Basalt is a hard, dark, igneous rock composed mainly of plagioclase, augite, and magnetite.) The wells are located in agricultural, low-density urban, and forest land-use areas, determined on the basis of visual observation at the time of sampling (table 2 [in pdf format]).
Water withdrawn from the 22 wells, located in four different hydrogeologic units in the Newark Basin, exhibited a high degree of chemical similarity. Samples from 14 of the 15 wells in the Passaic Formation had similar ion chemistry and could be classified as calcium-bicarbonate or calcium/magnesium-bicarbonate water. The one exception, a sample from station 403722075020201, seen as an outlier in the trilinear diagram (fig. 10), could be classified as calcium-chloride water. It had relatively higher concentrations of calcium and chloride and lower concentrations of magnesium and bicarbonate. Samples from two of the three wells in the Lockatong Formation could be classified as predominantly calcium-bicarbonate or calcium/magnesium-bicarbonate water. A sample from one of the three stations, 403611074570101, seen as an outlier in the trilinear diagram, had relatively low concentrations of calcium and bicarbonate and high concentrations of sodium and sulfate. Samples from the three wells in the Preakness Basalt could be classified as predominantly either calcium-bicarbonate or calcium/magnesium-bicarbonate water.
Samples from three wells contained concentrations of regulated compounds that exceeded their Maximum Contaminant Levels (MCL), defined by Federal Safe Drinking Water Act regulations (40 CFR Parts 141, 142, 143) and New Jersey Safe Drinking Water regulations (N.J.A.C. 7:10 - 1 et seq.). The sample from one well contained arsenic at a concentration of 57 micrograms per liter; the MCL for arsenic is 50 micrograms per liter. Samples from two wells contained concentrations of trichloroethylene of 1.13 and 14.3 micrograms per liter; the MCL for trichloroethylene is 1.00 micrograms per liter.
Nitrate-plus-nitrite nitrogen concentrations in samples from 22 wells ranged from less than 0.05 milligrams per liter, the laboratory reporting limit, to 7.0 milligrams per liter (table 2). In general, the concentrations of nitrate-plus-nitrite nitrogen in the ground water sampled in each land-use area and as indicated by the mean were highest in water from wells in agricultural land-use areas, and concentrations were higher in urban land-use areas than in forest land-use areas.
Dissolved oxygen concentrations in water from 22 wells ranged from less than 0.1 to 9.4 milligrams per liter (table 2). Anoxic water, with a concentration of dissolved oxygen of 1.0 milligrams per liter or less, was present in all three land-use areas. In general, the concentrations of dissolved oxygen in the ground water from each land-use area, as indicated by the mean, were lowest in water from wells in agricultural land-use areas, and concentrations were lower in forest land-use areas than in urban land-use areas.
Ground water obtained from 22 wells was analyzed for concentrations of VOCs. For 9 of 13 wells located in urban areas, 4 of 6 wells in agricultural areas, and 2 of 3 wells in forest areas, the one or more VOC compounds detected were present at concentrations equal to or greater than the laboratory reporting limits (table 2). The percentage of VOC detections is fairly uniform for all three land-use categories. VOC detections included estimated concentrations which are positive detections of a compound that are measured at less than the laboratory's minimum reporting limits. The detection frequency of each VOC compound is listed in table 3 [in pdf format].
Ground water from 21 wells was analyzed for concentrations of organic pesticide compounds. For 6 of 13 wells located in urban areas, 3 of 6 wells in agricultural areas, and none of 2 wells in forest areas, one or more organic pesticide compounds were detected at concentrations equal to or greater than the laboratory reporting limits (table 2). Detections include estimated concentrations. The detection frequency of each organic pesticide compound is listed in table 3.
The potability of ground water in the Coastal Plain of New Jersey depends primarily on its chemical quality, including contamination with saltwater. Chloride concentration is an accurate index of the extent and degree of saltwater contamination. The presence of high concentrations of chloride, however, is not definitive proof of active saltwater intrusion; high concentrations may represent a natural, static condition. Saltwater intrusion can be documented by analysis of periodically collected water samples. Saltwater intrusion is indicated by increases in chloride concentration over time rather than by a single concentration measured at one point in time.
In the 1940's, the USGS established a saltwater-monitoring network in the Coastal Plain of New Jersey to document the movement of saltwater into the freshwater aquifers. The USGS collects and analyzes water samples from USGS and NJDEP observation wells and selected domestic and agricultural supply wells. Chloride measurements are augmented by chloride-concentration data reported to the NJDEP by owners of public and industrial supply wells. During the 1998 water year, the USGS sampled water from nine wells in seven counties. Chloride concentrations in these samples were supplemented by more than 6,000 values that were reported by hundreds of public and industrial supply well owners and are stored in NJDEP and USGS files.
During the 1998 water year, saltwater intrusion was evident in many communities along Raritan Bay, the Atlantic Coast, the Delaware Bay, and the lower Delaware River, and in central Gloucester County.