How do we know there is a problem in the Appoquinimink Watershed and how big is the problem?

The 1972 Federal Clean Water Act requires that states develop a list of water bodies that need additional pollution reduction beyond existing controls.  These waters do not meet water quality standards for their designated uses.   Total Maximum Daily Loads (TMDLs) must be established for these water quality limited areas.  A TMDL is the maximum amount of a pollutant that a waterbody can assimilate and still meet water quality  standards.  Many of Delaware's waters, including the Appoquinimink River, are water quality limited or require additional pollution reduction to achieve water quality goals.

How do we know that the water quality goals are not being met?  Scientists test the water at various monitoring stations along our water bodies.  The results show which water quality parameters are being met.  When a TMDL needs to be established, the results from these water tests are incorporated into a model that simulates how the water body acts.  Scientists can then use the model to predict the levels at which pollutants must be reduced in order to sustain its uses, including aquatic life and recreational opportunities.

The pollutants and stressors that are causing water quality degradation in the Appoquinimink include excessive nutrients (nitrogen and phosphorus), low levels of dissolved oxygen, bacteria, and toxins (PCB's, dioxin, pesticides, and other materials).  Did you know that there are many places where you should not eat fish from the Appoquinimink River?  Examples of fish consumption advisories that have been issued for portions of the Appoquinimink Watershed include:

Currently, we are addressing a lack of dissolved oxygen and nutrient pollution.  When fish do not have enough dissolved oxygen available, they can become sick, have difficulty reproducing or even die. 

Nutrients can also lead to other undesirable conditions, such as excessive algae growth.  Too much algae can prevent light from penetrating the water, detracting from habitat value.  When algae die, the process of decay decreases dissolved oxygen in the water.   In keeping with most natural processes, the interconnections are complex and multi-facetted.

In order for nutrient levels to achieve water quality goals, 83.5 pounds per day or total nitrogen and 4.5 pounds per day of total phosphorus need to be removed from the water bodies in the Appoquinimink watershed.  In other words, we need to prevent the equivalent of 17 fifty-pound bags of 10-10-10 fertilizer from entering the water each day.   This means preventing 6,205 bags of fertilizer from being dumped into the water each year.  Of course, people are not actually dumping bags of fertilizer into the river and its tributaries, but we need to build a plan to reduce nutrients from entering our waters from runoff, septic systems, stormwater, erosion and other sources.