Mapping warm water sloughs on the South Platte

by Jeremy Sueltenfuss, CNHP Wetland Ecologist

For many years, our partners in the wildlife community have talked at length about the importance of warm water sloughs for overwintering Colorado wildlife.  As they are continually recharged by emerging groundwater, which is not subjected to the freezing temperatures at the surface, these stream-like features are some of the only water bodies across the landscape that remain open throughout the winter, providing wildlife much needed access to water during the cold winter months.  Because of their importance, we set out to map all the sloughs we could find along the South Platte River.  While aerial imagery can be quite good at mapping water features, nothing beats a low altitude flight to get a sense of the landscape!

Though familiar with the more common method of flying (being inside the plane that is), Jacqui thought she would give this method a shot.  It did not last long.  An immense thanks to Colorado Parks and Wildlife for supplying us with their plane and the CPW pilot, Brian, for a very safe and rewarding experience.  

Taking off in a small four seat prop plane from the Fort Collins – Loveland airport (Fort Love as our pilot referred to it), Jacqui, a fearless CNHP work-study student and I put our faith in our pilot, Brian.  Brian has been flying for Colorado Parksand Wildlife (CPW) for years, and his knowledge of both the landscape and local wildlife was tremendously beneficial.  Beyond his ability to spot herds of deer, gaggles of geese, and flocks of turkey from amazing distances, his stories from his work for CPW were breathtaking.  While I love hiking to remote mountain lakes, I have never thought about what it takes to stock them with fish.  Brian’s stories of maneuvering his small plane through tight mountain corridors, dropping his air speed to levels I personally never wish to feel while in flight, and releasing hundreds of small fish at precisely the right moment for them to land in the lake, all while watching the rock face in front of you fill your vision, was enough to make me sweat.  Luckily for us, the only aerial acrobatics we performed were slow broad circles to get a closer look at a slough, or a better view of some wildlife. 

Continually being recharged by groundwater, warm water sloughs remain slightly warmer than other surface waters and remain open throughout the winter.  This provides much needed access to water for wildlife in the area.

Though “Colorful Colorado” is quite brown in the winter, flying at 150 feet over the South Platte was fascinating and beautiful.  As promised, sloughs seemed to be the only open water around, and the leafless trees afforded views of the many flocks of waterbirds, small herds of deer bounding away, and even a few scenes of male turkeys doing their best to impress a nearby female.  The seven bald eagles we saw perched in trees or soaring above the river provided a wonderful example of an Endangered Species Act success story and served as tribute to the tremendous effort of conservation groups over the past 50 years.  It was enough to almost forget what we were after!  Armed with maps of sloughs we had completed before the flight using imagery from the summer, we constantly compared what was in our maps to what we were seeing on the ground.  Both Jacqui and Brian seemed to do quite well looking down at maps and back out at the landscape for 4 straight hours.  While I did my best to appear absolutely normal, my stomach was reenacting what it must feel like to stock those high mountain lakes!  Queasiness aside, we accomplished our goal and came away with a highly accurate map of the warm water sloughs along the South Platte River between Greeley and the state line.  Though many other riparian landscapes across the state contain warm water sloughs that may one day be mapped, I have high hopes this data can be used for the restoration and the conservation of lands containing these important features.