State of the Millstone 2018

December 28th, 2018

Seventy years ago, when The Watershed Institute was first founded, streams in central New Jersey were in peril. Unsustainable agricultural practices caused fertile soils to erode from the land and smother aquatic habitats.

As agricultural land was converted into growing suburban developments, polluted stormwater runoff from sprawling impervious surfaces further threatened water quality. Protective wetlands, forests, and open spaces were destroyed and paved over.

Fortunately, forward-thinking volunteers created our organization to help protect and restore water quality and habitat in our part of the state. Trees and shrubs were planted by the thousands, land along streams was preserved, and new regulations were secured to address these problems.

We continue this decades-old legacy to this day. The StreamWatch volunteer monitoring program has tracked water quality in the Millstone Watershed since 1992. Teams of volunteers collect monthly chemical data from a network of about 40 sites across the Millstone watershed, as well as summer bacteria counts and semi-annual macroinvertebrate samples from a dozen sites.

Water quality is ever-changing and is responsive to changes in the landscape. Between 1930 and 2012, urban land increased from just 12% to more than 40% of the Millstone Watershed. How are our streams faring in response? We seek to answer this question by reviewing StreamWatch data collected between 2014 and 2018.

An overall grade was determined for each of 14 subwatersheds using eight different parameters. While the individual parameter grades ranged from A through F, the overall grades for water quality health were between B and D, as shown by the map.

Three subwatersheds received the highest grades of B. Among these higher quality subwatersheds, Upper Stony Brook and Beden Brook share headwaters protected by the Sourland Mountain Preserve. The third, Six Mile Run, actually has more forested land in its subwatershed than it did a few decades ago, which is a rare occurrence in central New Jersey. High amounts of dissolved oxygen in the streams here have led to flourishing macroinvertebrate life.

Lower grades were found primarily amongst the subwatersheds of the Upper Millstone River. The Route 1 corridor that splits the Millstone Watershed generally serves as the dividing line between the rocky streams of the Piedmont in the west and the muddy and sandy bottom streams of the coastal plain to the east. The Upper Millstone River Watershed is located within the coastal plain, and is marked by low dissolved oxygen and pH levels, high bacteria counts, and poor macroinvertebrate communities.

Two subwatersheds with the highest amounts of impervious surface coverage have the least amount of water quality data. We are unable to grade Royce Brook and Duck Pond Run this year due to a lack of volunteer participation in those areas, so they have been given an ā€œIā€ for incomplete. In order to make a full watershed assessment in the future, we will need the help of a few new citizen scientists.

Would you be excited to bring home this report card? With half of the Millstone subwatersheds below a C average, there are clearly some changes that must be made in central New Jersey to make our waterways healthier. We must reduce the impacts of polluted stormwater runoff through impervious cover reduction, restoration projects, and stronger municipal regulations. At home, River-Friendly practices can go a long way.

Just five of the eight available parameters are shown in the report card. The full report is available here. Visit to find scores for individual monitoring sites and our grading methodology.


The StreamWatch program is funded by Janssen Pharmaceuticals, Inc. For more information about StreamWatch and joining our volunteer monitoring program, contact Nik Hansen at [email protected]

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