River temperatures still exceeding advised levels | AspenTimes.com

River temperatures still exceeding advised levels

ASPEN – The temperature of water in local streams and rivers is still occasionally exceeding a state standard for healthy trout despite recent rains and slightly cooler weather, the Roaring Fork Conservancy has discovered.

During the week of Aug. 5, water was in excess of 68 degrees at four monitoring stations – the Crystal River near Colorado Rocky Mountain School in Carbondale, the Roaring Fork River near the Carbondale boat ramp, Brush Creek near the Snowmass Village rodeo roundabout, and the Roaring Fork River at the East Hopkins Avenue footbridge in Aspen.

The conservancy, a Basalt-based nonprofit organization, launched a program June 28 where it monitors water temperatures throughout the Roaring Fork basin. Fifty volunteers had collected more than 440 temperature readings at 21 locations by early August for the Hot Spots for Trout program.

The program was started because the drought has been so severe that it is diminishing stream flows and increasing temperatures. The conservancy provides its findings to Colorado Parks and Wildlife so officers can limit fishing in areas where fish and other aquatic life are stressed.

Heather Tattersall, land and water conservation specialist with the conservancy, said the recent changes in the weather – with several days of cloudy conditions and occasional rain – haven’t eased problems generated by low water levels.

“It takes a lot of days to influence what’s happened over the last six to eight weeks,” she said.

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The monitoring has produced results that were expected, Tattersall said. Higher temperatures are anticipated downvalley because of hotter weather and low flows. When there is less water quantity, it warms up faster, Tattersall said.

The Roaring Fork River also tends to warm up higher in Aspen because so much water is diverted just above town, creating a low flow. The river cools down again as more water comes in at Castle and Maroon Creeks and, especially, from the Fryingpan River.

Temperatures in the Fryingpan River rarely climb to levels experienced in the other rivers because cool water is released from Ruedi Reservoir, Tattersall said. Monitoring earlier this month showed temperatures in the 50s in the upper and lower Fryingpan River, she said.

The temperature of the water determines what can survive in it. Aquatic species have evolved to live at certain temperatures ranges, according to the conservancy. For example, brown-trout adults thrive at temperatures from 54 to 66 degrees. In the upper and lower limits of that range, an organism becomes stressed, meaning it could be at a competitive disadvantage for food and more susceptible to disease or even death.

Temperature also influences both water biology and chemistry. Temperature affects how much oxygen is in the water. Elevated temperatures lead to decreased oxygen levels, which negatively impact aquatic plants and fish.

The state standard for temperature in the Roaring Fork Valley is a maximum of 68 degrees. Colorado Division of Parks and Wildlife is authorized to close sections of the river if the daily maximum temperature exceeds 74 degrees or if the average daily temperature exceeds 72 degrees.

No restrictions have been placed on Roaring Fork basin rivers at this point. The conservancy is asking anglers to use common sense – avoid fishing when temperatures are highest between 3 p.m. and 7 p.m. Play a fish quickly when caught, release it quickly and keep it in the water the entire time. While the precautions might take some of the immediate satisfaction out of fishing, it will pay dividends, Tattersall said.

“It’s going to be good in the long run,” she said.

scondon@aspentimes.com