Overview of the potential effects of forest management on low flows in snowmelt-dominated hydrologic regimes

Abstract

This paper reviews potential effects of forest management on low flows in snowmelt-dominated hydrologic regimes. The hydrologic response of low flows to forest management was found to be highly variable in magnitude, time, and space. Forest management generally increases water volume—no case studies relevant to snowmelt-dominated regimes reported a decrease in water quantity as a result of forest harvesting. In areas where fog drip occurs, a decrease in water volume contributing to low flows might be observed. The longevity of increased water quantity is infrequently discussed in the literature specific to snowmelt dominated regimes. A few authors, however, have commented on expected longevity of response based upon analysis of literature not specific to snowmelt-dominated regimes. These authors generally report a return to pre-treatment low flow levels within 3–6 years with the re-establishment of vegetation.

The review identifies many knowledge, research, and extension needs. Knowledge of low flows is hampered by an incomplete understanding of generation processes, particularly those relating to subsurface flow, evapotranspiration, and the interrelated effects of forest practices and climate change. Forest management is only one of many human activities that can potentially affect a watershed�s hydrologic regime. Because natural processes and human activities occur simultaneously, studying the sole effects of forest management on low flows is difficult. Limitations in low flow science around measurement methodologies, scaling of results, and inadequate research design are noted.