Delaware River and Delaware Estuary Nutrient Criteria Plan (pdf 327 KB; December 2013)


A nutrient is any substance assimilated by living things that promotes growth. The term is generally applied to nitrogen and phosphorus, although it can also be applied to trace nutrients like silica and iron. While nutrients are good at certain levels, high concentrations can overstimulate the production of plants and algae, which utilize dissolved oxygen as they decompose, therefore reducing oxygen levels in the water. This leads to poor conditions in streams and reduced water quality. According to the U.S. EPA, "High levels of nitrogen and phosphorus in our lakes, rivers, streams, and drinking water sources cause the degradation of these water bodies and harm fish, wildlife, and human health."

Nitrogen and phosphorus pollution comes from fertilizers, animal waste, septic systems, storm runoff, and sewage treatment plants. This type of pollution is reported to be a problem in more than half of the water bodies in the nation, including the Delaware Estuary which has an area of reduced dissolved oxygen in the urban river corridor. Elevated levels of nitrogen have been identified as a potential cause. 

DRBC serves as the lead coordinating agency among the U.S. EPA and the states of New York, New Jersey, Pennsylvania, and Delaware for evaluating nutrient conditions in the shared interstate waters of the Delaware River and the Delaware Estuary. The DRBC also is the lead agency in determining the nutrient criteria or nutrient-related criteria, if appropriate, that are needed to protect aquatic life, public & industrial water supplies, and recreational uses of these shared resources.

DRBC is currently working to identify appropriate levels of nutrients and necessary measures to take, especially in relation to dissolved oxygen. To address both nutrients and dissolved oxygen, a process has been initiated to measure the point sources of nutrients and oxygen-depleting materials and to build a water quality model to integrate this information and forecast future scenarios for the Delaware Estuary. Although the results from such efforts are not yet available, the goal is to select an appropriate path towards a healthy, functioning ecosystem in all parts of the Delaware Estuary.

Nutrient Management Initiatives

In August 2008, the DRBC's Water Quality Advisory Committee tasked its Nutrient Management Subcommittee with the following:

  • Evaluating and recommending interim protective measures
  • Determining designated uses to be protected
  • Reviewing current monitoring and identifying needs
  • Reviewing options and approaches for establishing effects-based nutrient criteria or other management options

Current Major Nutrient-Focused Initiatives Include:

  • Point Source Nutrient Monitoring in the Delaware Estuary (see below)
  • Non-Point Source Loading to the Delaware River & Delaware Estuary (see below)
  • Delaware River (Non-Tidal) Bioassessment (see below)
  • Creation of an Expert Panel to advise the WQAC and the DRBC on the development and use of a Delaware Estuary Eutrophication Model; authorized by Resolution 2012-07 (pdf 31 KB)
Point Source Nutrient Monitoring in the Delaware Estuary



Related DRBC Publications:

Non-Point Source Loading to the Delaware River & Delaware Estuary

Nutrients are a natural and an essential component of aquatic ecosystems. A key step in evaluating nutrients and their effects in the Delaware River & Delaware Estuary will be the quantification of the background rates of nutrient loading from the landscape, both from natural weathering processes and from enhanced anthropogenic sources.

This effort is expected to combine empirical measurements with large-scale models to determine both the absolute and relative contributions from different sources.

Delaware River (Non-Tidal) Bioassessment

The ecological condition of the aquatic communities within the Delaware River is expected to be the river’s most sensitive indicator of nutrient enrichment.

The Delaware River Basin Commission has been working since 2001 to develop a system-specific method of evaluating both the benthic macroinvertebrate communities and the benthic periphyton (algae) communities of the Delaware River to assess the ecological health of the river. Learn more.

Bioassessment Work Products:

BOD(ultimate) Requirement for DRBC Nutrient Monitoring

DRBC Ad Hoc Workgroup's Recommendations for BODultimate (November 2013; pdf 67 KB)


Among the worst possible symptoms from elevated nutrient conditions in streams, lakes, and coastal systems is the depletion of dissolved oxygen from the water column. The Delaware Estuary has a long history of dissolved oxygen issues, with a complete lack of oxygen in the estuary near Philadelphia extending for months each year during the 1960s. This dissolved oxygen sag in the estuary’s urban corridor has traditionally been attributed to point-source loading of oxygen-depleting compounds, which are grouped into two main categories: CBOD (carbonaceous biochemical oxygen demand) and NBOD (nitrogenous biochemical oxygen demand). To address the severe conditions of the 1960s, the DRBC adopted a wasteload allocation for CBOD in 1968. With the support of the states and the federal government, in part through Clean Water Act grants, the implementation of this CBOD allocation has resulted in a remarkable recovery in dissolved oxygen conditions in the Delaware Estuary’s urban corridor.

Despite this remarkable recovery, the dissolved oxygen levels in the estuary at times remain far below equilibrium saturation values and may create stressful conditions for the fish and other aquatic life of the estuary. Yet the relative roles of nutrient enrichment, point source loading of CBOD and NBOD, and the background non-point source loading of oxygen-demanding materials remain unclear. The nutrient monitoring program as a whole begins to resolve this uncertainty through quantification of the point source loading, which will be combined with other efforts into a quantitative model of the estuary dynamics. This “eutrophication model” will allow the separation of the relative importance of the various components that depress oxygen levels. One of the key parameters for such a model is the long-term, or “ultimate”, biochemical oxygen demand (BODultimate). Yet BODultimate has not been a traditional parameter for effluent monitoring, and no labs in our region currently perform this test. Nevertheless, because short-term measurements of BOD and CBOD can underestimate the long-term oxygen demand, and this bias can vary substantially among facilities and through time, the resolution of the current dissolved oxygen issues in the Delaware Estuary require evaluation of this long-term, or ultimate, biochemical oxygen demand.

BODultimate Requirements:

BODultimate monitoring will be required for the 20 largest CBOD allocations in Zones 2 through 5 of the Delaware Estuary; these facilities account for 95% of the estuary's CBOD wasteload allocation. Monitoring will be required twice during the two-year monitoring window: once during summer conditions (scheduled for summer 2015) and once during winter conditions (expected in winter 2015-2016).

Because no laboratories in the Delaware Valley region currently conduct the BODultimate test (see Standard Methods 5210C), the Water Quality Advisory Committee recommended - and the DRBC convened - a working group to identify the necessary steps for this monitoring effort. The Workgroup's Recommendations (pdf 67 KB) provided the additional specificity needed to complement Standard Methods 5210C, and both documents have been used to develop Standard Operating Procedures (SOP) for consistent application of the test.

These BODultimate data will be used in conjunction with the 2-year nutrient monitoring data to lay the foundation for a Eutrophication Model of the Delaware Estuary.