Streamflow from small watersheds on the western slope of the Cascade Range of Oregon

Abstract

Streamflow from small watersheds on the western slopes of the Oregon Cascade Range is strongly influenced by a maritime climate (wet winters and dry summers). Although annual precipitation is high (94 inches in the study area), overland flow is almost unknown. Peak flows result largely from subsurface flow and under conditions in which both retention and detention reservoirs are almost filled during extended periods of low-intensity rainfall. Under these conditions, vegetation appears to exert a minimum influence on high streamflow. Lowest streamflow occurs from late August to mid-November and may follow a 60-to 100-day period with little or no rain. The dense vegetation of this part of the Douglas-fir region appears to exert its major influence at such times. Removal of vegetation from only 30% of a 250-acre watershed has caused a 12-28% increase in minimum streamflow. On a 237-acre watershed on which 80% of the trees were cut, the increase in low flow was 85%.

Maximum entropy production: can it be used to constrain conceptual hydrological models?

“…For a detailed description of the watershed the reader is referred to e.g. Rothacher (1965); Rothacher et al (1967) or Tague and Band (2001). Here we give only a short description.…”

Forest roads: a synthesis of scientific information.

“…Roads do not appear to affect annual water yields, and no studies have evaluated their effects on low flows. In some studies, roads produced no detectable change in flow timing or magnitude (Rothacher 1965, Wright and others 1990, Ziemer 1981, but in other basins, average time to storm peak advanced and average peak magnitude increased after road building for at least some storm sizes (Harr and others 1975, Jones and Grant 1996, Thomas and Megahan 1998. In a study in Idaho, peak stormflow magnitude increased in one basin and decreased in another after road building, an effect the authors attribute to subsurface flow interception by roads and desynchronization of delivery of water to the basin outlet (King and Tennyson 1984).…”

“…Of those studies that have attempted to look at the hydrologic behavior of roads, most have been part of small (typically 0.3 to 2 square miles) watershed experiments, where roads were a component of the experimental treatment, which often included other silvicultural practices. Key studies and locales of this type include those by Rothacher (1965Rothacher ( , 1971Rothacher ( , 1973, Harr and McCorison (1979), Harr and others (1975), Jones and Grant (1996), and Thomas and Megahan (1998) in western Oregon; Ziemer (1981Ziemer ( , 1998 and Wright and others (1990) in northern California; King and Tennyson (1984) in central Idaho; Reinhart and others (1963), Hewlett and Helvey (1970), others (1982, 1988) in the southern Appalachians, Helvey and Kochenderfer (1988) in the central Appalachians;and Hornbeck (1973) and Hornbeck and others (1997) in the northern Appalachians. Very few studies have focused on the hydrologic behavior of roads alone; in the Pacific Northwest and Rocky Mountains, maximum measurement periods during which roads were the only treatment range from 1 to 4 years (Wemple 1994).…”

Land-cover impacts on streamflow: a change-detection modelling approach that incorporates parameter uncertainty

“…Past process-based hydrological investigations at HJA have focused on runoff generation (Harr, 1977), snowmelt and snow accumulation (Harr, 1986;Berris & Harr, 1987), catchment nutrient budgets (Sollins et al, 1980), and water residence time (McGuire et al, (Rothacher, 1965;Harr & McCorison, 1979) and sediment transport (Grant & Wolff, 1991). HJA is also the location for much of the analysis from Jones & Grant (1996) and the papers that followed (Beschta et al, 2000;Jones & Grant, 2001;Thomas & Megahan, 1998;2001) debating the interpretation of results of statistical analyses of paired-catchment data.…”