Simulating long-term landcover change and water yield dynamics in a forested, snow-dominated Rocky Mountain watershed

Abstract

Changes in the extent, composition, and configuration of forest cover over time due to succession or disturbance processes can result in measurable changes in streamflow and water yield. Removal of forest cover generally increases streamflow due to reduced canopy interception and evapotranspiration. In watersheds where snow is the dominant source of water, yield increases and advanced peak discharge are attributed to increased snow accumulation, and enhanced melt rates in forest openings. Because knowledge of long-term watershed-level streamflow responses to landcover dynamics is limited by relatively short-term gage data, we present a modeling approach that combines existing vegetation and hydrologic simulation systems to evaluate these interactions. Our findings suggest that both vegetation and hydrologic characteristics of the research watershed are at the limits of their estimated natural ranges. Although species composition remained fairly stable over time, the size and connectivity of current landcover patches are at the upper end of the estimated temporal distribution. The large proportion and continuous nature of forest cover associated with current conditions coincide with water yield, peak discharge rates, and flow variability that are at the low end of their modeled distributions. The integrated modeling approach we describe should be applicable in other ecosystems given knowledge of biophysical interactions and availability of appropriate data. By gaining an understanding of the possible range of variability due to natural conditions, management plans may be designed to maintain resources within estimated and desirable bounds.

Citation

Ahl, R. S.; Woods, S. W. 2006. Simulating long-term landcover change and water yield dynamics in a forested, snow-dominated Rocky Mountain watershed. In: Junlander, Randall; McGurk, Bruce, eds. Western snow conference: Proceedings of the 74th annual western snow conference; 2006 April 17-20; Las Cruces, NM. Brush Prairie, WA: Western Snow Conference. p. 127-134.