Graduation Date
Summer 2026
Document Type
Thesis
Program
Master of Science degree with a major in Natural Resources, option Forestry, Watershed, & Wildland Sciences
Committee Chair Name
Andrew Stubblefield
Committee Chair Affiliation
Cal Poly Humboldt Faculty or Staff
Second Committee Member Name
Jim Graham
Second Committee Member Affiliation
Cal Poly Humboldt Faculty or Staff
Third Committee Member Name
Jo Archibald
Third Committee Member Affiliation
Cal Poly Humboldt Faculty or Staff
Keywords
Northern California, Water, Watershed, Climate, Climate change, Forests, Storage
Subject Categories
Watershed Management
Abstract
The climate is changing, with rising temperatures projected to increase vegetation stress and mortality. Precipitation is also expected to become more extreme, with longer dry seasons intensifying droughts, and wetter wet seasons increasing the risk of landslides or floods. Summer baseflows in northern California are declining, and a shift in water availability may alter vegetation communities, resulting in mortality and species composition changes. These trends highlight the need for increased attention and management to be focused on evaluating and maintaining watershed water storage to maintain ecosystem health.
This study estimates water storage capacity using a water balance approach, drawing in trends from soil moisture and climate data, in the context of climate resiliency, at 19 primarily small, forested watersheds in northern California. Storage was tracked through time, maximum storage and discharge trigger point values were estimated, and trends in soil moisture and climate metrics were assessed for each watershed. Maximum storage capacity varied between watersheds, ranging from 322 to 1330 mm, and was found to be significantly correlated with median watershed slope and two elevation metrics, indicating that in this region, a steeper watershed will generally store more water. Previous research has shown that a potential mechanism behind this is the highly weathered bedrock present in the Coastal Belt, allowing for deep storage and prolonged baseflows. The use of remotely sensed evapotranspiration and precipitation data for calculating the water balance was found to perform relatively well, matching expectations from previous similar studies, as a means of comparing multiple watershed’s storage capacities and behavior. However, uncertainty in daily change in storage estimates was found to be up to 10 mm per day, resulting in potential accumulating errors through the calculation period. Soil moisture data from the focused study sites showed differing trends in storage persistence through the soil profile, adding insight into watershed storage behavior at a point-scale. Remotely sensed soil moisture from 2010 to 2023 was found to have a significant decreasing trend in inland northern California, while no significant trend was detected in coastal northern California. Using climate projection data, three temperature metrics were found to have a significant increasing trend at all study watersheds, with the most warming happening in the dry season. Precipitation was found to have a significant seasonal sharpening trend, with an increase in precipitation during the wet season, and a decrease in precipitation in the dry season. These findings indicate that in the face of changing climate, steps should be taken to assess and maintain water resources to protect ecosystem and human health. The methods utilized offer ways to approach assessing watershed climate resiliency, and are best used in concert to prioritize watersheds where active management like thinning or prescribed burning could be most effective.
Recommended Citation
Gressierer, Christopher Gerard, "Assessing water storage in Northern California forests" (2026). Cal Poly Humboldt theses and projects. 2600.
https://digitalcommons.humboldt.edu/etd/2600