Fraser, Colorado rivers being monitored for high temperatures
August 14, 2008
Anglers and others using the Fraser and Colorado Rivers in Grand County are asked to not touch a number of underwater electronic sensors being used to monitor the temperature of the water.
The sensors have been placed in the two rivers as part of the work of the Grand County Water Information Network, a nonprofit group working to preserve the quality of the streams as fish habitat.
“We have 25 of the sensors starting from the headwaters of the Fraser, just south of Mary Jane, all the way down the Colorado River to County Road 39 outside of Kremmling,” said Bob Weiby, the network’s Field Operations Manager. “We’re using the sensors to help determine anything that might be influencing the water temperature.”
Weiby is concerned that a couple of the sensors have been deliberately pulled out of the river in recent weeks. His assumption is that fishermen or other visitors to the rivers did not know what the devices were.
The equipment consists of the electronic sensor itself, which is a metal disc-shaped device about the diameter of a 50-cent coin, and a short piece of PVC pipe used as the sensor’s protective cover. Both the sensor and PVC pipe are attached by a nylon cord to a heavy iron plate that acts as an anchor to keep the equipment under the water.
“We’re asking the public that when they see our sensor equipment in the water to please leave it alone,” Weiby said. “When it’s pulled out of the water and is exposed to the air, the temperature readings become polluted. The public needs to know that these devices are important in our fight for the health and well-being of our rivers.”
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The different sensors are set to record stream temperatures at intervals of 5 to 30 minutes. The data is periodically downloaded by Weiby and then analyzed by Sarah Clements, a scientist working with the Grand County Water Information Network. That information is then submitted to a number of agencies including the Denver Water Board.
Rising water temperatures in streams and rivers affect the survivability of fish. Weiby explained that local water temperatures should be between 47 and 55 degrees in the summer. However, in recent years, temperatures have been rising into the high 60s.
A 73 degree Fahrenheit temperature was recorded July 25 in Ranch Creek in the Fraser Valley.
“That’s a real red-flag temperature,” he said. “There’s no fishing in a stream with temperatures that high because the fishing are hiding under embankments or any shade they can find. Fish mortality is high.”
While warm, dry air temperatures are one factor, another is the increasing amount of water being taken out of the streams by users. When water levels drop in streams and rivers, the temperature of the remaining water rises.
“Low flow is the No. 1 cause because there is not enough water in the streams,” Weiby said. “This is due almost entirely to the increasing demands on our water resources.”
By taking regular temperature readings, the Grand County network has informed water users about the situation. Users have sometimes responded by taking less water from the streams to help preserve the habitat.