From Green to Clean: Closed Loop Lake System

The Lakes at Duke Farms. The Raritan River can be seen at the top of the photo.

The Lake System at Duke Farms. The Raritan River can be seen at the top of the photo.

Written By: Jon Wagar, Director of Operations.

Duke Farms is hard at work trying to change our lakes from green to clean. As anyone who visits the property during the summer sees, our man-made lake system contains excessive amounts of algae and aquatic vegetation. It not only is an aesthetic issue, but it provides less than optimal habitat for wildlife and can lead to fish kills.

There are several things that cause the growth of algae and other vegetation. With hydrological consultants from Princeton Hydro and engineers from MWH, we’ve developed a 3 phase multi-year project to help address this problem. The first phase, the installation of a new well to provide water to the reservoir, was completed in mid-August.

This power station is where the hydro-electric power for Duke Farms was generated. The pumping house had a capacity of one million gallons per day. A pipe laid under the river connected the pumping house to the two million-gallon Duke Reservoir.

The pumping house had a capacity of one million gallons per day. A pipe laid under the river connected the pumping house to the two million-gallon Duke Reservoir.

Previous to installation of the well, Duke Farms pumped approximately 700,000 gallons of water a day from the Raritan River to the Duke Reservoir, our highest-elevation lake. Water pumped to the Reservoir flows by gravity through all the lakes and back into the Raritan River. Amazingly, like much of the infrastructure at Duke Farms, this River pumping was originally designed by James Buchanan “Buck” Duke and still works over hundred years later!

Although there is plenty of water in the river and we replace at least as much as we take out, the water quality is not great. River water contains nutrients from runoff from agriculture and lawns upstream as well as other non-point source pollutants. It also tends to be fairly warm, and warm water holds lower levels of oxygen. These nutrients may be good to grow lawns and corn, but when they runoff into the river they also grow aquatic vegetation and algae.

New Lake System Well

New lake system well installed near Duke Reservoir.

The water from the new well will initially replace some, but not all, of the water that we pump from the River. Well water is much cleaner than the river water, is colder and holds more oxygen, and will help starve the excessive aquatic vegetation of nutrients while also providing better habitat for fish and other aquatic organisms. We also hope that eventually, we can stop pumping from the river altogether.

The second phase, which we recently begun, will entail the installation of a recirculation pump that will pump water from the lowest elevation lake back to the reservoir. The recirculation pump will cause increased flow of water between the lakes and therefore decrease the nutrients that are leached out of the sediment in the lake bottoms. Once it is fully functional, it should also allow us to completely stop pumping from the Raritan River.

Third, we are exploring the harvesting of algae and other aquatic weeds to reduce the nutrient load in the lakes. Since these plants contain excessive amounts of nutrients, we also plan to add them to our composting operations, where we actually can use these nutrients to make richer compost for our community garden and incubator farm.

The final phase will be installation of bubblers. Bubblers will increase dissolved oxygen near the bottom of the lakes and also help stop nutrients from the sediment from leaching into the water.

Stay tuned as we continue to make our improvements to our lakes and make them more appealing for wildlife and people!

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