Water Towers

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Digging a snow pit to measure temperature, snow density, and snow grain qualities at various depths in the snow cover profile.
Tim Bardsley

Scientists at NWT have documented how high-elevation mountain ecosystems serve as "water towers" to store seasonal snow until it is released later in the year during snowmelt runoff. Every year this melting snow provides large quantities of high quality water that drives the economy and the ecology of the western United States.

Much of our research at NWT LTER is related to how changes in climate may affect snow properties, and in turn how changes in snow properties relate to ecosystem changes.

High elevation ecosystems act as “water towers” that store seasonal snow until it is released during snow melt runoff, providing large quantities and high quality water that drive the economy and the ecology of the western US.

A recent evaluation of our climate record from 1954 to 2006 shows that Niwot Ridge is experiencing abrupt and asynchronous climate change, with the subalpine forest warmer and drier during all seasons, while the alpine tundra has experienced longer growing seasons, warmer summers, and cooler and wetter winters (Clow 2010).

Ice thickness measured in late March over a 20-year interval shows a statistically significant thinning of winter lake ice cover that is best explained by increased winter snowfall and warmer water temperatures, leading to increased flows into the lake in fall and winter (Caine 2002).

Liu et al. (2004) used geochemical and water isotope tracers to show that less than half of the annual streamflow in the Green Lakes Valley is “new water” from snowmelt; groundwater is much more important in high-elevation catchments than previously thought. High-altitude aquifers honeycomb parts of the Colorado Rockies, trapping snowmelt and debunking the myth that high mountain valleys act as “Teflon basins” to rush water downstream.

Ice thickness for an alpine lake, Green Lake 4, showing a decline in ice depth (and duration) over time (updated from Caine 2002).
For further reading: 
Caine, N. 2002. Declining ice thickness on an alpine lake is generated by increased winter precipitation. Climatic Change, vol 54 pp. 463-470.
Clow, D.W. 2010. Changes in the timing of snowmelt and streamflow in Colorado: A response to recent warming. Journal of Climate, vol 23 pp. 2293-2306, doi:10.1175/2009JCLI2951.1.
Liu, F.; Williams, M.W.; Caine, N. 2004. Source waters and flow paths in an alpine catchment, Colorado Front Range, United States. Water Resources Research, vol 40 , W09401, doi:10.1029/2004WR003076.
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