Passaic & Metropolian Watershed Studies

County: Passaic

Town: Wanaque

The North District Water Supply Commission (NJDWSC) contracted Najarian Associates to perform a water quality assessment to characterize water quality conditions for the NJDEP’s Passaic Watershed Management Areas (WMAs 3, 4 & 6), a large and diverse watershed with numerous wastewater discharges and water supply withdrawals.

Technical Servies

Najarian’s tasks included data acquisition, statistical analysis, and point/nonpoint assessment. Najarian acquired separate data from the USGS and water purveyors’ extensive monitoring programs. The NJ engineering firm assessed their compatibility and merged the data from these disparate sources. Next, Najarian conducted a series of statistical analyses which assessed long- and short-term trends, seasonal differences and the relationship between water quality and streamflow.

Passaic Watershed Results

Results indicated that long-term beneficial trends in water quality had leveled off in recent years and that there was a clear and inverse relationship between concentration and flow for a number of parameters.

Agency data was used to determine the cumulative magnitude of the point source discharge at various points in the watershed, resulting in a unique approach to assess the watershed’s total and non-point loads. Recognizing (from prior studies) that certain parameters were quasi-conservative, Najarian developed a mass-balance model based on the upstream discharge load, known streamflows and a simple estimation of non-point sources. The firm then used this model to simulate four years of Total-P data on a daily basis and compare it to the discrete measurements of in-stream concentrations.

As illustrated, the agreement between the simulated and observed data was quite good. This simulation highlighted the level of impact that point sources have on the in-stream water quality.

Metropolitan Watershed – (WMA7)

County: Union

Union County contracted Najarian to be part of the team developing the Characterization Study for the Metropolitan Watershed (WMA 7), a highly urbanized watershed and tributary to Arthur Kill and Newark Bay. 

Technical Services

While the tasks and analyses were similar to those conducted for the Passaic Watershed project listed above, the approach was tailored to local conditions.

Metropolitan Watershed Results

The study revealed reduced, non-point source impacts to local receiving waters due to extensive sewering to regional treatment facilities that discharge to portions of New York Harbor.

Results indicated that the local streams largely met State criteria and that water quality conditions were improving. This finding encouraged a re-direction of effort toward stream corridor protection programs.