Garrett Hartley: Life of a Dammed River

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It was extremely energy draining as I sat in the WRFI van melting into my seat due to the extreme heat we experienced while driving into northern Arizona to Navajo Bridge. Upon arriving at Lee’s Ferry campground I was forced to leave the air conditioned van into the even hotter and drier world outside. Coming from the coastal community of Laguna Beach, the lack of water to swim in to lower my body temperature has definitely been the hardest part of this course for me. Luckily on this day I was told by my instructors that the Colorado River had a chilling temperature of about 45 degrees and if we wanted we could run down for a dip.

A few other students and I immediately took advantage of the opportunity and quickly made our way down to the shoreline. Once we arrived at the small beach I noticed an extremely murky section of water extending about six feet from the shoreline before jutting up to crystal clear blue water of the main water flow. I had noticed many fly fishermen standing in the murky water casting their lines only to the clear water. What I experienced next really intrigued me and provoked even more questions.

As I prepared for the cold water, to my surprise this strange murky layer was incredibly warm! Then at the merging of the murky brown and clear blue there was a bone chilling, skin numbing change of what seemed like a twenty degree difference of temperature. Why is there such a drastic change in temperature? Does the increase in sediment result directly in a higher heat capture? Telling my instructor James about this, he informed me that the murky water is the Paria River merging with the crystal clear blue water of the Colorado River. Why is there such a difference between two rivers flowing in the same general area? What are the effects of this difference?

Just up river from Lee’s Ferry is the Glen Canyon Dam which splits the Colorado’s flow into an upper and lower basin. Craig Child’s writes an article specifically addressing the effects of the Glen Canyon dam and how “when rivers are slowed by dams, the water can no longer carry its sediment.” Furthermore he explains “the Colorado used to carry about 90 million tons a year through the Grand Canyon…it now carries about 15 million tons.” What effects does this loss of sediment have on the environment?

“A Biological Mandate” by the United States Geological survey described how four native fish once endemic to the Grand Canyon are now endangered or extinct. The humpback Chub, Razorback Sucker, Colorado Squawfish, and Bonytail all face major threats from altered water chemistry, flooded habitat from reservoirs, and predation from introduced non-native fish. After asking a fisherman what he was trying to catch, he told me trout which is a non-native species introduced after the dam’s construction. After dams are constructed, fish hatcheries will often be put in place.

Looking at this day when I saw the confluence of the Paria River and the Colorado I can see the direct effects of how a dammed river looks compared to a non-dammed river. Naturally rivers like the Colorado have a very diverse watershed and if we keep imposing changes to the watershed with things like dams the system will suffer. Low sediment levels result in changes to water chemistry which in turn affects the native species ability to thrive.

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