Impact of coastal fog on gage height in an old growth redwood forest - Prairie Creek, Redwood State and National Parks

Author

Koa Lavery

Graduation Date

2015

Document Type

Thesis

Program

Other

Program

Thesis (M.S.)--Humboldt State University, Natural Resources: Forestry, Watershed and Wildland Studies, 2015

Committee Chair Name

Kristine Brenneman

Committee Chair Affiliation

HSU Faculty or Staff

Keywords

Humboldt State University -- Theses -- Natural Resources

Abstract

Streams have a diurnal fluctuation in quantity of flow that corresponds with rates of evapotranspiration. As much as 45% of water consumed by California coastal redwoods (Sequoia sempervirens) appears to come from fog. The relation between fog and gage height was investigated for the first sixteen precipitation-free days of July, 2013 in the old growth portion of Prairie Creek Watershed in coastal northwestern California (Redwood National and State Parks). Satellite imagery was used to determine presence of fog and a pressure transducer was used to determine gage height in Prairie Creek near the confluence with Boyes Creek. This study tested the hypothesis that as fog increased, the diurnal fluctuation and typical summer downward trend of gage height (as a measure of stream flow) would be disrupted. A positive relation between fog and gage height was found. The relation between average daily fog coverage of watershed and diurnal fluctuation in gage height had an R squared of 0.3261. Fog coverage and time of day maximum gage height occurred had an even higher correlation (R squared 0.5295). Time of maximum gage height varied between 7am and 1pm. Gage height peaked later in the day when more of the watershed was covered in fog. A lag in gage height response to fog coverage was a confounding factor. Stream measurements that represented changes over greater time spans (one day) showed a higher correlation with fog coverage than did metrics on shorter time scales (30 minutes) (R squared 0.5295 vs 0.06430 respectively). Although the obvious short term variation in gage height is a few millimeters, a few millimeters is 2% to 3% of total flow and Prairie Creek is a relatively small stream. The implications of a continual 2%-3% change over multiple years or on large streams and rivers could send a massive ripple through riparian ecosystems. Ultimately, this research supports a long held belief that fog has an impact on streams.

https://scholarworks.calstate.edu/concern/theses/tx31qk95t

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