IMPACT OF COASTAL FOG ON GAGE HEIGHT IN AN OLD GROWTH REDWOOD FOREST - PRAIRIE CREEK, REDWOOD STATE AND NATIONAL PARKS By Koa Lavery A Thesis Presented to The Faculty of Humboldt State University In Partial Fulfillment of the Requirements for the Degree Master of Science In Natural Resources: Forestry, Watershed and Wildland Studies Committee Membership Dr. Kristine Brenneman, Committee Chair Dr. Alison O’Dowd, Committee Member Dr. Raymond Burke, Committee Member Dr. Alison O’Dowd, Graduate Coordinator December 2015 ABSTRACT IMPACT OF COASTAL FOG ON GAGE HEIGHT IN PRAIRE CREEK IN AN OLD GROWTH REDWOOD FOREST Koa Lavery 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 ii 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. iii ACKNOWLEDGEMENTS Thank you to two people who died while this thesis was in progress, my mom and Suzie Seeman. They both had an amazing appetite for learning and I am still working to digest all they shared with me. I fully appreciate my committee sticking with me over the years and Bud Burke for keeping up with the project so he was able to officially jump in at the end; it has been a saga. Thanks to Dr. B. for improving my grammar and teaching me about water bears. Thanks to Alison for recognizing what I ment to say and figuring out how to say it as well as helping me meet deadlines. Moral support from my dad and Aunt Lynette who spent a summer sitting next to me and the computer trouble shooting was essential. Thanks to Joe Seney for giving me the idea to investigate fog. Since this thesis took over seven years to complete the list is too long to include everyone who helped me wade through the infinity of thoughts to nail a few down on paper; some of the people who were crucial to completing this project are Anjii Hansen, Katie Wilson, Wes Smith, Mat Lavery (diagnosing major computer issues for months), Judy Wartella, Vicki Ozaki, Alicia Torregorsa, and Mel Nordquist. iv TABLE OF CONTENTS ABSTRACT ........................................................................................................................ ii ACKNOWLEDGEMENTS ............................................................................................... iv LIST OF FIGURES ........................................................................................................... vi INTRODUCTION .............................................................................................................. 1 Redwood utilization of fog ............................................................................................. 3 Relation between Photosynthetically Available Radiation (PAR), Evapotranspiration and Streamflow Dynamics .......................................................................................... 5 Streamflow Diurnal Fluctuation ................................................................................. 5 Redwood use of fog .................................................................................................... 6 Fog Impact on Streamflow ............................................................................................. 8 Fog Detection ................................................................................................................ 10 Materials and methods ...................................................................................................... 13 Study Area .................................................................................................................... 13 Stream Gage Measurements ......................................................................................... 16 Satellite Imagery to Detect Fog .................................................................................... 17 RESULTS ......................................................................................................................... 22 Streamflow Measurements ........................................................................................... 22 Comparison of Fog and Gage Height ........................................................................... 26 DISCUSSION ................................................................................................................... 37 Recommendations ............................................................................................................. 41 REFERENCES ................................................................................................................. 44 Personal Communication Citations................................................................................... 51 v LIST OF FIGURES Figure 1. Prairie Creek watershed in Redwood National and State Parks (Humboldt County, CA). Green triangle shows Prairie Creek above Boyes Creek (PAB) gaging station. Graphic created in ArcGIS 10.1 .......................................................................... 14 Figure 2. GOES-15 satellite image taken on July 1, 2013 at 6:15pm. Turquoise polygon is Prairie Creek watershed. White pixels are fog moving onto coast from ocean. Each pixel is 1 km2. ................................................................................................................... 19 Figure 3. Shows Geos-15 image taken on July 1, 2013 at 6:15pm. Image on the left shows pixels before classifying as fog, and not fog. Image on right shows pixels that have been reclassified as fog on left side of image (in green) and pixels reclassified as not fog on right side of image (in salmon). Turquoise line is boundary of Prairie Creek watershed. ......................................................................................................................... 20 Figure 4. Comparison of gage height (dotted line) measured on Prairie Creek above Boyes Creek (PAB), and precipitation (solid line) measured in Orick at station MORIC1. The graph reveals a period with no precipitation between July 1 and 16, 2013. This period was used to investigate fog impact on gage height. All data points after July 16, 2013 were removed due to a decrease in sensor resolution by a factor of ten from 0.03 centimeters (thousandths of a foot) to 0.3 centimeters (hundredths of a foot), and spikes (e.g. July 17 and August 8) in data that are associated with sensor removal from stream. ........................................................................................................................................... 23 Figure 5 Rating curve for Prairie Creek above Boyes (PAB). Eight discharge measurements were made by Redwood National Park personnel between June 12th and August 19th to construct this rating curve. At least two points (i.e. 25% of the points) did not follow the trend line. R squared = 0.9265. ................................................................ 25 Figure 6. Comparison of raw and detrended gage heights for Prairie Creek above Boyes Creek (PAB) shows the best fit line (fit to raw data) for July 1 through July 17, 2013. The equation for the best fit line was used to remove the downward trend in flow to enable comparison of flows on different days without the impact of decreasing groundwater flow. Dashed red line shows raw gage heights. Solid blue line shows detrended gage heights. ..................................................................................................... 26 vi Figure 7. A comparison of the percentage of fog covering Prairie Creek watershed detected in each satellite image (blue line) and daily average fog detected in each satellite image (red dashed line) between July 1 and 16, 2013 are similar. July 4, 5, 13, and 14 had no fog as noted by a star. ...........................................................................................