The ‘teflon basin’ myth: hydrology and hydrochemistry of a seasonally snow-covered catchment

Abstract

Background: Snow and ice melt provide sensitive indicators of climate change and serve as the primary source of stream flow in alpine basins.

Aims: We synthesise the results of hydrological and hydrochemical studies during the period 1995–2014, building on a long history of earlier work focused on snow and water on Niwot Ridge and the adjacent Green Lakes Valley (GLV), which is part of the Niwot Ridge Long Term Ecological Research site (NWT LTER).

Methods: These studies are discussed in the context of how snow, snowmelt and runoff reflect changing local climate. We review recent results of snow, snowmelt, hydrology and hydrochemistry from the plot to the basin scale, utilising new tools such as continuous global positioning system (GPS) measurements of snow depth, along with remotely-sensed measurements of snow-covered area and melt, combined with long-term measurements of snow properties, discharge and solute and isotopic content of water.

Results and Conclusions: Surface–groundwater interactions are important components of water quantity and quality in alpine basins. Some or most snowmelt infiltrates underlying soils and bedrock, transporting soil and bedrock products to surface waters. Infiltrating snowmelt, along with increased melt of stored ice, increases the hydrologic connectivity between the terrestrial and aquatic systems. Alpine basins are being impacted by increases in atmospheric nitrogen deposition, which has caused changes in soil microbial processes such as nitrification. Nitrate, dissolved organic carbon and dissolved organic nitrogen are thus flushed from soils and talus to streams. Our long-term results show that alpine catchments, such as Green Lake 4 at NWT LTER+, have the greatest sensitivity and least resilience to climate warming, with any warming leading to increased water yields.

Keywords:

• Green Lakes Valley
• hydrochemistry
• hydrological modelling
• hydrology
• Niwot Ridge
• snow

Acknowledgements

We thank Craig Skeie, Water Resources Facility Manager, City of Boulder Watershed, for his many years of help, assistance and support. We are grateful for the data and logistical help provided by the NSF-sponsored NWT Long Term Ecological Research (LTER) project and the University of Colorado Mountain Research Station.

Additional information

Funding

Support for Mark W. Williams during the writing of this manuscript was from NSF Dust on Snow [EAR 1124576 and EAR 0934647] and NSF WSC programme.

Notes on contributors

Mark W. Williams

Mark Williams is a hydrologist; he is interested in mountain ecology and hydrology. He is currently the Principal Investigator of the NWT LTER programme.

Fengjing Liu is a hydrologist with keen interests in watershed hydrology, isotope hydrology and water quality.

Eran Hood

Eran Hood is a biogeochemist with interests in aquatic ecosystems within seasonally snow covered and glacial watersheds.

Noah P. Molotch

Noah Molotch is a hydrologist with interests in land-atmosphere interactions, ecosystems, and remote sensing. He is Director of the Center for Water, Earth Science and Technology at the University of Colorado.

Nel Caine

Nel Caine is a geomorphologist and hydrologist with a keen interest in mountain environments.

Rory Cowie

Rory Cowie is a mountain hydrologist who also works on acid mine drainage problems.