Keeping the Upper Delaware River Tailwaters Cool

As summer settles into the Upper Delaware River (UDR) watershed, anglers and conservationists alike begin paying closer attention to one critical factor: water temperature. While warm sunny days are welcomed by many, rising air temperatures can create challenging conditions for the wild trout that thrive in the cold waters of the Upper Delaware River tailwaters.

Fortunately, while no one can control the weather, there are effective strategies in place to help protect this world-class trout fishery during periods of summer heat. These efforts fall into two broad categories: reservoir management and stream restoration.

One of the most important tools available today is the UDR Thermal Bank. Established in 2017 as part of the Flexible Flow Management Program (FFMP), the Thermal Bank represents years of advocacy by the Upper Delaware conservation community. Recognizing the importance of maintaining suitable water temperatures for trout, the four Delaware River Basin states and New York City, collectively known as the Decree Parties, agreed to reserve a dedicated volume of water specifically for temperature management.

Each year, 2,500 cfs-days of water are set aside in the New York City Delaware Basin reservoirs. During the warm season, the New York State Department of Environmental Conservation monitors a variety of factors, including weather forecasts, cloud cover, precipitation, and river flows. When conditions indicate that water temperatures may approach the critical threshold of 75 degrees Fahrenheit at the USGS gauge in Lordville, New York, the DEC can direct New York City to release water from the Thermal Bank.

Managing the Thermal Bank requires a careful balance of science, experience, and forecasting. Since its creation, the program has been remarkably successful. Water temperatures have consistently been maintained below the established threshold, and despite several challenging summers, including the exceptionally hot conditions experienced in 2022, the Thermal Bank has never been completely depleted. As climate patterns continue to evolve and concerns about long-term warming grow, conservation groups are actively exploring ways to strengthen and potentially expand the program to meet future challenges. 

Beyond reservoir operations, significant work is also taking place directly within the watershed. Over the past decade, Friends of the Upper Delaware River (FUDR) and Trout Unlimited have led an ambitious stream restoration effort throughout the UDR tailwaters. These projects address a wide range of watershed needs while providing important benefits for water temperature management.

Riparian buffer installations, tree planting initiatives, and streambank stabilization projects all contribute to cooler, healthier streams. Trees and streamside vegetation provide shade that reduces solar heating, while stabilized banks help maintain natural channel conditions and improve habitat quality. Together, these restoration efforts create more resilient ecosystems capable of supporting healthy populations of wild trout.

This summer, those efforts will continue with a full-time field conservation program throughout the watershed. Teams of young conservation professionals will spend their days collecting data, assessing stream conditions, and identifying future restoration opportunities. Their work will help build a roadmap for projects that deliver multiple ecological benefits, including improved habitat, enhanced water quality, and cooler stream temperatures.

The success of these initiatives depends not only on agencies and conservation organizations but also on the angling community. Many Upper Delaware anglers already understand the importance of monitoring water temperatures and adjusting their fishing practices during periods of warm water. Sharing that knowledge with new anglers can make a meaningful difference. Simple actions such as avoiding fishing during the hottest parts of the day, minimizing fish handling time (Keep them wet!), carrying a stream thermometer, and paying attention to the USGS stream gages that monitor temperature conditions help reduce stress on wild trout populations. There are also warm water species anglers can target in the UDR tailwaters such as smallmouth bass and walleye that are great gamefish and can make for an enjoyable day. Finally, it’s important to note that most stream biologists believe that UDR trout are able to successfully find cold water refuge during heat spells but angling during these periods adds further stress and should be curtailed. 

Protecting the Upper Delaware River's cold-water fishery is a shared responsibility. Through innovative reservoir management, ongoing habitat restoration, and responsible angling practices, the conservation community continues to safeguard one of the nation's premier wild trout rivers. As summer temperatures rise, these combined efforts help ensure that the Upper Delaware remains a thriving fishery for generations to come.