Friends of Northern Lake Champlain Water Quality Monitoring

The headwaters of the Rock River are in East Highgate, Vermont. From there, the river generally flows north, crossing the Canadian border before changing course and running south, back into Vermont before it empties into Lake Champlain near Highgate Springs. The Rock River consists of 37.4 total stream miles, while its watershed spans 56.4 square miles between Vermont and Quebec.

You can use the interactive map to the right to zoom in and out to different places where the Rock River flows.

The Rock River is listed in the  State of Vermont 2018 303(d) List of Impaired Waters  due to its high levels of nutrients and sediment.

Nitrogen and phosphorus are essential for plant and animal growth and nourishment, but too many nutrients in water can cause negative health and ecologic effects.

In the case of Lake Champlain and many other freshwater systems, the excess of phosphorus combined with warm temperatures and calm weather conditions has resulted in the excess plant growth and reoccurring toxic cyanobacteria blooms that we see in the summer months on Lake Champlain.

Due to its impaired state and the efforts to reduce phosphorus loading to Lake Champlain, there has been tremendous resources and work directed towards the Rock River watershed over the past two decades. Best Management Practice (BMP) implementation, such as cover cropping, reduced or no tillage, counter-slope strip cropping, forage and bio-mass planting, and innovative nutrient management has been widely implemented.

From 2011-2018, water quality sampling that FNLC conducted at two sites on the Rock River with VT DEC financial support, showed no detectable change or trends in total phosphorus (TP), dissolved phosphorus (DP), total suspended solids (TSS), and particulate phosphorus (PP). This is despite fact that the Vermont Clean Water Initiative (Act 64) was passed in 2015 and the new  required agricultural practices (RAPs)  were put into effect in 2016.

While many BMPs were implemented throughout the watershed, water quality improvements have not been observed in the Rock River. The stable loading trends do not necessarily show that the BMPs implemented are ineffective. It is possible that we may not yet have reached critical mass of implementation, or that it may take more time for excess or legacy phosphorus to leave the system. Either way, FNLC is dedicated to implementing better practices in and around our rivers and on our lands.

Following the 2018 water sampling results, FNLC has continued collecting water samples to further assess conditions on the Rock River and engaging in promoting water quality methods with stakeholders.

In 2022 with support from the VT DEC, FNLC increased our sampling sites to four sites within the Rock River watershed across 26 total events. The samples were tested for total phosphorus (TP) and dissolved phosphorus (DP).

We also emphasized collecting samples during high flow events. Compare the image to the right with the image above. Both were taken at the same sampling site on the Rock River but during much different days and seasons. Look at the difference in water color and height of the water.

Collecting samples when the river is flowing high (like in the image to the right) is important to understand nutrient levels in varying conditions. As you may imagine, the concentration of nutrients in the river is typically much higher during heavier precipitation events. As you can see in the image to the right, the water looks almost like chocolate milk due to all the sediment suspended in the water.

By expanding our sampling in the Rock River to four sites in 2022, we began to see segments of the river with higher phosphorus results than others, but ultimately we wanted data in finer detail.

In 2023, FNLC began work on our  Lake Champlain Basin Program (LCBP)  funded project to study and assess the impacts of ditches and tributaries on the Rock River. We plan to better understand the source of stressors in the watershed and the effectiveness of the agricultural BMPs implemented in the Rock River watershed. The study includes two years of water sampling at a total of 10 sites, partnering with an environmental consultant to complete the ditch and tributary assessments, and meeting with landowners and farmers within the watershed to discuss successes and shortcomings of the agricultural BMPs.

Water sampling began during the summer of 2023. By having more sites to sample at, our goal is to better understand the sources of phosphorus so that we can help implement BMPs, reduce erosion, and restore water quality before the river empties into Lake Champlain.

FNLC staff members are currently heading out to collect water samples every other week and whenever  the Rock River USGS gage  alerts us that the river is in its high flow state. The water samples are analyzed by the Vermont Agriculture and Environmental Laboratory (VAEL) in Randolph for total phosphorus, dissolved phosphorus, and total nitrogen.

Phosphorus can be found in agricultural and lawn fertilizers, manure, human and animal waste, and in many more places. Phosphorus can also be transported when streambanks are eroded since phosphorus can be bound to soil particles that eventually make their way downstream. Phosphorus that is bound to other particles is often called particulate phosphorus and takes longer to become accessible for cyanobacteria to grow. Meanwhile, dissolved forms of phosphorus, like those found in fertilizers and wastewater treatment effluent, are much more readily available to cyanobacteria.

Through our water sampling data, we are able to begin to understand if the majority of phosphorus is in dissolved or particulate forms, and if there are certain times throughout the year that one is higher than the other.

For example, if particulate phosphorus is much higher than dissolved phosphorus in a certain segment of the river, we can start to predict that streambank erosion is more of a problem than the land use practices and work to address those issues first.

We can also use elevated total nitrogen results as an indicator that fertilizers or sewage are contributing to the runoff entering the river and being transported by it, since fertilizers and sewage are common sources of nitrogen in water.

The dissolved phosphorus samples that we collect are required to be filtered so that the particulate phosphorus that is bound to sediment and other fine particles are not included in the analysis. During high flow events, the filter is often covered with sediment, as seen in photo to the right. This may help to give you an idea of how much sediment is suspended and being transported in the water during these events.