Surface water acidification responses and critical loads of sulfur and nitrogen deposition in Loch Vale watershed, Colorado
Article first published online: 29 JAN 2005
Copyright 2005 by the American Geophysical Union.
Water Resources Research
Volume 41, Issue 1, January 2005
How to Cite
2005), Surface water acidification responses and critical loads of sulfur and nitrogen deposition in Loch Vale watershed, Colorado, Water Resour. Res., 41, W01021, doi:10.1029/2004WR003414., , , and (
- Issue published online: 29 JAN 2005
- Article first published online: 29 JAN 2005
- Manuscript Accepted: 30 NOV 2004
- Manuscript Revised: 21 OCT 2004
- Manuscript Received: 11 JUN 2004
- critical loads;
 We evaluated the sensitivity of The Loch, a subalpine lake in Rocky Mountain National Park in Colorado, to acidification in response to increased atmospheric loading of sulfur (S) and nitrogen (N) using the Model of Acidification of Groundwater in Catchments (MAGIC). Lake water acid-base chemistry was moderately sensitive to changes in both S and N deposition. However, the loads of S deposition that would drive chronic lake water acid neutralizing capacity (ANC) to below 0 or 20 μeq L−1 were estimated to be 11 and 8 kg S ha−1 yr−1, respectively, assuming constant future N deposition at current levels. Comparable loads for N deposition, assuming constant future S deposition, were estimated to be 21 and 12 kg N ha−1 yr−1, respectively. Modeling results for Andrews Creek, an alpine tributary to The Loch, suggested critical loads for surface water acidification that averaged about one third lower. Surface water ANC = 50 μeq L−1 was projected to occur in 50 years in The Loch if S or N deposition increased by a moderate amount (<40%) but could not be achieved in Andrews Creek by reducing either S or N deposition to zero. On the basis of the results of synoptic surveys of lake water chemistry, about one fifth of the wilderness lakes in the Colorado Front Range are more acid-sensitive than The Loch. This modeling exercise suggests the need for a regional analysis of critical loads for the larger population of acid-sensitive aquatic resources in order to provide part of the scientific foundation for federally mandated land management decisions.