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Wildfires and Our Mountain Streams
With the arrival of fall colors, wildfire season in the West is on the retreat. It’s important to look back on the toll these fires have taken on Colorado’s watersheds. In 2015, wildfires burned a record-breaking 10.1 million acres across the U.S., according to High Country News. We’ve seen a similar magnitude of burns this summer from California to Idaho and in our own backyard with the Hayden Pass, Cold Springs near Boulder, Beaver Creek and Sylvan Lake fires. Aside from the risks to houses and human lives, wildfires also pose threats to our watershed and river systems.
Wildfires have been scorching the earth as long as humans have existed. They are a natural force that keeps our ecosystems in check and natural cycles in motion. As human populations grow and encroach into wild places, wildfires have left that balance teetering. In mountain communities, our local firefighters, Forest Service, and water providers continuously monitor and manage the risks.
Increasing global temperatures means an increase in forest fires in the West, putting greater pressure on our natural resources, including water systems. So what kind of effects are they having on our rivers?
LOW TO MODERATE INTENSITY
Fires, when low-to-moderate in intensity, can actually maintain the long term health of forest and riparian ecosystems by facilitating vegetation succession, which leads to diverse riparian zones. Diversity and regrowth in riparian banks is essential in maintaining bank stabilization and the natural filtration capabilities of native plants. High water flow, flooding, and a surge in nutrients can provide natural habitat for fish reproduction, and can load organic matter that can spike productivity. When these fires are lower intensity, and even prescribed as a forest management tool, they carry on healthy, natural processes.
The most detrimental effects to a watershed from high intensity fires are excessive erosion and runoff. Unburned forests act like sponges with rainfall, with the healthy vegetation and litter absorbing water and protecting the soil layer from intense rain. The plant layer slows down the water’s speed as it runs towards the river. The loss of vegetation after a burn leads to greater-exposed, loose soil and less absorption leading to higher runoff volumes. Some plants even release a waxy, water-resistant cover after being burned, further decreasing the forest’s absorptive capacity.
These effects can last years following a fire. The increased runoff leads to flash flooding as river banks overflow with excess volumes. Ash, woody debris, and sometimes fire retardant chemicals are flushed through our rivers, loading pollutants such as phosphorus, nitrate, and ammonia into our water systems. Increased runoff and loss of plants leads to stream banks eroding, adding on to increased sedimentation in our rivers which negatively effects spawning fish and can even clog their gills.
All of this harms aquatic insect life, water temperatures, fish habitat and reproduction, fisheries, and irrigation systems. Increases in sediment load can also put additional pressures on drinking water treatment processes and congest reservoirs downstream of the burn.
Our local firefighters and wildland specialists can only do so much to manage the force of fire — it’s essential to be proactive and aware yourself. Heed fire warnings and bans, fully put out fires while camping, and do not store your firewood on your deck. Homes should be surrounded by fire breaks, or 200 feet of defensive space between their perimeter and the nearest trees. Home consultation services, such as REALFire, exist in our valley to best protect where we live and work. More information can be found at http://www.realfire.net. If, as expected, our county population doubles by 2050, the wildland-urban interface will continue to be tested severely, but deliberate, responsible measures can prevent adding unnecessary risks to our already threatened watershed.
Lizzie Schoder is the education and outreach coordinator for Eagle River Watershed Council. The Watershed Council has a mission to advocate for the health and conservation of the Upper Colorado and Eagle River basins through research, education and projects. Contact the Watershed Council at 970-827-5406 or visit http://www.erwc.org.