LONG‐TERM CHANGES IN STREAMFLOW FOLLOWING LOGGING IN WESTERN OREGON AND ASSOCIATED FISHERIES IMPLICATIONS¹

Abstract

The long-term effect of logging on low summer streamflow was investigated with a data set of 36 years. Hydrologic records were analyzed for the period 1953 and 1988 from Watershed (WS) 1 (clearcut logged and burned), WS 2 (unlogged control), and WS 3 (25 percent patch-cut logged and burned) in the H. J. Andrews Experimental Forest, western Cascade Range,Oregon. These records spanned 9-10 years before logging, and 21-25 years after logging and burning. Streamfiows in August were the lowest of any month, and were unaffected by occasional heavy rain that occurred at the beginning of summer. August streamfiows increased in WS 1 compared to WS 2 by 159 percent following logging in WS 1, but this increase lasted for only eight years following the start of logging in 1962. Water yield in August for 1970-1988 observed from WS 1 was 25 percent less than predicted from the control (WS 2, ANOVA, p=O.O32).Water yield in August increased by 59 percent after 25 percent of the area of WS 3 was patch-cut logged and burned in 1963. In contrast to WS 1, however, water yields from WS 3 in August were consistently greater than predicted for 16 years following the start of logging, through to 1978. For the 10 years, 1979-1988, water yield observed in August from WS 3 was not different than predicted from the control (WS 2, ANOVA, p-O.l'75).The contrasting responses of WS 1 and 3 to logging are thought to be the result of differences in riparian vegetation caused by different geomorphic conditions. A relatively wide valley floor in WS 1 allowed the development of hardwoods in the riparian zone following logging, but the narrow valley of WS 3 and limited sediment deposits prevented establishment of riparian hardwoods.Low streamflows during summer have implications for salmonid survival. Reduced streamfiow reduces the amount of rearing habitat, thus increasing competition. Combined with high water temperatures, reduced streamfiow can lead directly to salmonid mortality by driving salmonids from riffles and glides, and trapping them in drying pools. Low streamfiow also increases oxygen depletion caused by leaves from riparian red alders. (KEY TERMS: streamfiow; logging; salmonids; water use; water storage; evapotranspiration; dissolved oxygen.)

Assessing the Impact of Forest Change and Climate Variability on Dry Season Runoff by an Improved Single Watershed Approach: A Comparative Study in Two Large Watersheds, China

“…Some studies have demonstrated that forest loss can increase dry season runoff since the removal or death of forests can reduce evapotranspiration and canopy interception in disturbed sites and ultimately increase soil moisture and groundwater recharge [9]. Meanwhile, other studies have reported that fast vegetation regrowth and soil disturbances after forest harvesting may offset the water increment or even decrease dry season runoff [6,8,10]. Similarly, variable responses of dry season flow to afforestation or reforestation have also been found, which are mainly determined by the changes in soil properties caused by forest regrowth and forest practices [11,12].…”

Camp Creek Revisited: Streamflow Changes Following Salvage Harvesting in a Medium-Sized, Snowmelt-Dominated Catchment

“…Numerous studies have attempted to quantify the potentially negative impacts of different forest practices on hydrology, water quality and aquatic habitat (e.g., Hicks et al, 1991;Macdonald et al, 2003) as well as the potential benefi ts in the form of increased water yield through forest management, particularly in relation to effects on snow accumulation and melt (e.g., Rich, 1972;Gottfried, 1991;Troendle et al, 2001). The prospect of widespread salvage harvesting in response to the current outbreak of mountain pine beetle in British Columbia has produced concern about the potential for negative hydrologic changes.…”

Proceedings of the coast redwood forests in a changing California: A symposium for scientists and managers

“…Second, the lack of buffer strips increased light in riparian zones, increasing growth at sites where plants may disproportionately affect summer flow by removing water directly from the hyporheic zone. Third, regrowth along the South Fork included many red alders (Alnus rubra), which tend to use more water than conifers (Hicks et al 1991). Fourth, a young, dense, rapidly growing age cohort may simply use more water than a mature stand (Moore et al 2004).…”