According to the Washington State Forest Practice Rules, perennial streams are defined
as “flowing waters that do not go dry any time of a year of normal rainfall” (WAC-222-16-30
(3)). The uppermost point of perennial flow (UMPPF) is considered the upper extent of a
perennial stream segment. UMPPF locations can either be found at transition points between Np
(perennial streams) and Ns (non-perennial) streams or at the channel head of a stream. The latter
possibility was a more common finding amongst studies in Washington State examining the
question of UMPPF locale (Veldhuisen, 2003; Jaegar et al., 2007; Hunter et al., 2005). Though
UMPPFs are more commonly concentrated at or near stream channel heads, identifying these
points can still sometimes be challenging, as hydrologic and weather conditions can vary both
inter-annually and intra-seasonally (Hunter et al., 2005).
Natural variation in perennial stream dynamics has been explored, but few studies in the
state have looked at UMPPF dynamics as a result of a controlled disturbance, such as clearcut
timber harvesting, which has been shown to affect hydrologic regimes and water yield
(Rothacher, 1970). This study aims to compare differences in UMPPF dynamics and locations
pre and post clearcut harvesting.
Mostovetsky, A., 2017. Mostovetsky 2017 Pre and Post Harvest Assessment of Uppermost Points of Perennial Flow in the Lower Skagit Watershed. Skagit River System Cooperative, La Conner, WA. pp. 5.
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