The Rocky Mountains supply water to more than 60 million homes in the West, but this crucial water shed is in peril due to a tiny insect called the mountain pine beetle. Scientists Reed Maxwell of Colorado School of Mines and John Stednick of Colorado State University have teamed up to study the impact of the mountain pine beetle on water quantity and quality in the area. "Sustainability: Water" is produced in partnership with the National Science Foundation.
Sustainability- Water – Dead Trees and Dirty Water in the Rockies
ANNE THOMPSON reporting:
Renowned for their dramatic snow-capped peaks and thick pine forests, the Rocky Mountains supply water to more than 60 million people in the West. But this crucial watershed is in peril due to a tiny insect called the mountain pine beetle, a species of bark beetle.
JOHN STEDNICK (Colorado State University): Roughly 90% of the lodge-pole pine in the state of Colorado has been killed by the bark beetle. So we’re talking about 4.5 million acres of trees.
THOMPSON: This loss of trees has changed more than just the landscape of the West.
REED MAXWELL (Colorado School of Mines): We’ve changed the balance of the watershed because we’ve killed some of the trees.
THOMPSON: With funding from the National Science Foundation, hydrologists Reed Maxwell from Colorado School of Mines and John Stednick from Colorado State University are leading a team of scientists to study the impact of bark beetle tree-kill on water quantity and quality.
STEDNICK: One of the things that we’re trying to look at is how this is affecting the water quantity and quality in the Rocky Mountains. So right now in the state of Colorado, about 2.5 million people are affected. Their drinking water can potentially be affected by the pine beetle epidemic.
THOMPSON: The bark beetles are native to North America and are not harmful under normal circumstances. But warmer temperatures and drought over the past ten years have led to a population explosion of beetles. And that has changed three major processes of the water cycle in Colorado - snow pack, runoff and what's called "evapotranspiration."
STEDNICK: Evapotranspiration is a combination of evaporation and transpiration.
MAXWELL: That’s interrupted with beetle-killed trees. And this is complicated because the beetle-killed trees don’t transpire anymore, and so that will change the water cycle.
THOMPSON: Healthy pine trees, through transpiration, draw groundwater into their roots and leaves and release it into the atmosphere during photosynthesis, almost like sweat. Beetle-killed trees cannot transpire which leaves more water in the ground, to eventually run off. And dead trees have no pine needles to intercept snow and help shade the snowpack from the strong Colorado sun.
MAXWELL: We get a deeper snow pack because there’s less foliage to intercept. And we have that snow pack melting off more quickly because there is less shading.
THOMPSON: Without shade, more water from snow or rain evaporates, or becomes vapor, forming clouds in the sky and leaving less water to melt and runoff to streams. The combination of less evapotranspiration and earlier snowmelt means a shorter snow season in Colorado - increasing the amount of water yield in the early spring, and leaving the soil drier in later months.
Yet, the dead trees are not only affecting the quantity of water, but the quality as well.
STEDNICK: The dead trees, the dead forests, they basically will release and have needle fall over a period of time. Those needles on the forest floor will start to decompose.
THOMPSON: Decomposing pine needles mix with runoff to form a smelly, bad-tasting "pine tree tea." By doing field collection and lab analysis on stream and runoff water, Stednick and Maxwell discovered that these fallen needles are causing a change in the natural chemical make-up of Colorado's drinking water.
LINDSAY BEARUP (Colorado School of Mines): We’re looking for metals and we’re looking for organic compounds as well as potentially nitrogen.
THOMPSON: While not necessarily harmful, organic compounds have to be balanced delicately when pre-treating water for consumption. Changes in organic carbon levels could lead to unsafe drinking water.
In fact, Maxwell and Stednick's team have measured higher levels of organic compounds in the soil beneath trees killed by bark beetles than in the ground under healthy trees.
MAXWELL: There’s always needles that drop onto the ground and decompose. But we see a much greater amount of litter and tree-fall and stem-fall and then that tree eventually falls over. So we see a big change in the carbon balance.
THOMPSON: While the water in Colorado is still safe to drink, more research is still needed to determine the extent of the damage these organic compounds are causing.
STEDNICK: What is the long-term effect? What is the legacy of these bark beetles? How long is this organic material production or decomposition and production of organic carbon in the rivers going to last?
THOMPSON: Earlier runoff and snow melt periods, combined with less evapotranspiration, and "pine tree tea," are likely to be part of the challenge of sustainable water in Colorado for several years. All because of a tiny bug.
The drought-stricken Colorado River Basin has gotten some temporary relief in the past few weeks after winter storms have pounded the region with fresh rain and snow. In fact, as the Los Angeles Times reported, the recent precipitation has caused federal water managers to lower their estimates of the risk of water shortage in the near future.
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