Eagle River Watershed Council: Have you noticed all the bugs this summer? | VailDaily.com

Eagle River Watershed Council: Have you noticed all the bugs this summer?

James Dilzell
The Current
Macroinvertebrates, like this adult mayfly, are critical to our watershed — acting as indicators of overall river health and food for aquatic life, birds and other animals.
Special to the Daily


That word alone can send a spine shivering for some, as they consider all of the creepy crawling insects we encounter on a daily basis — like mosquitoes, black flies, ticks (OK, that last one is technically an arachnid, but causes me to run. Fast).

But in the world of water, we love bugs. Benthic macroinvertebrates, or insects lacking a spine and large enough to see with the naked eye that start life in the water, are critical food for fish and help to tell us about the health of a stream. In Eagle County, the most common species of these insects include mayflies, caddisflies, stoneflies, scuds, snails and midge flies.


James Dilzell

Starting as larvae, they spend most of their maturing lives in the stream-bottom sediments, attaching to rocks, algae or submerged wood. Here, they break down and consume algae, bacteria and organic matter, like leaves and plants, as they move from egg to larvae to pupa. Once they become fully grown, most will become land dwelling, or terrestrial, as they search for mates. Then, females will return to the water to lay their eggs.

Since they spend so much time in the water, good water quality is critical to the health of these species.

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In fact, water quality is so critical for them that they are an official measurement in Colorado’s multimetric index for bioassessment, which is used to monitor stream quality. This is because each species has varying tolerance to pollution, and the presence or absence of each species can inform us about certain aspects of water quality.

Multimetric index scores, which are calculated using a variety of biological measurements, help to determine to what level a stream is meeting water quality standards and whether the river is biologically stressed or not. While the scores do not indicate the cause of water quality issues, it can trigger further investigation into that stream or river to find out what might be impacting it.

Some of the most impactful pollution sources in our community include stormwater runoff and lawn chemicals. The latter includes both fertilizers and pesticides used on landscaping, which, when used in excess, can make their way into our rivers. Fertilizers can create a bloom in algae (potentially toxic kinds) and block out macroinvertebrate’s rocky habitat.

Pesticides used on terrestrial bugs will unfortunately also work on aquatic insects, causing them to die. Stormwater runoff is an ever-increasing threat, and can include a slew of pollutants, like motor oil, trash, salts and even organic matter in our runoff. As we develop more land, more stormwater runoff is created and sent to our rivers, often untreated. Always remember — only rain down the drain.

Pete Wadden, watershed education coordinator for the town of Vail, has seen improvement in bug populations in the last five years along Gore Creek. Why? Wadden explains: “The biggest factor has been a reduction in landscaping chemicals. Just like you would get a second opinion from a doctor if he prescribed an invasive procedure, I encourage people to get a second opinion before they have an arborist or chemical applicator put pesticides on their trees.”

Here in Eagle County, our streams are monitored for water quality around the clock through the Watershed Council’s Water Quality Monitoring and Assessment Program. But, once a year, our streams undergo a macroinvertebrate sampling process to help round out the water quality snapshot.

Overall, water quality within Eagle County is OK, but there is certainly room for improvement. Most of the river segments in the county are in attainment now with the lowest scores in the upper stream segments simply because there is more water in the river as you move downstream, which provides dilution, but bug scores are trending downward for the most part.

To help, it is going to take our whole community to adopt proper fertilizer and pesticide application techniques, allow only rain to flow down our storm drains and, thereby, protect our rivers.

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