philomathia logo
Gabrielle Boisramé – Philomathia Fellowship Recipient at Berkeley

Growing up in a small farming community in California, I’ve always been aware of the complicated issues surrounding water in this state. During long dry stretches in the summer, it’s hard to find enough water for wildlife, farmers, and communities to all get what they need. I decided to study environmental engineering at UC Berkeley so that I could help solve some of these pressing water issues.

Once in Berkeley, I was lucky enough to be asked to join a project studying hydrology in the Sierra Nevada. This project often involves leaving campus on short notice for fieldwork, which would be nearly impossible if I had to teach every semester to fund my studies. Thanks to the Philomathia fellowship, I had the flexibility needed to complete this research. This flexibility also gave me the time to mentor undergraduate students experiencing research for the first time.

My research merges two seemingly opposite elements: fire and water. The Sierra Nevada is adapted to frequent wildfires caused by lightning, but human fire suppression has led to forests becoming overgrown. These dense forests have high water demands and risk of extreme fires due to large fuel loads.

My research takes place in the Illilouette Creek Basin of Yosemite National Park, a unique place where, since 1972, managers have allowed most naturally ignited fires within the Basin to burn themselves out instead of extinguishing them.

A large part of my research included mapping vegetation changes in Illilouette Creek Basin using historical aerial photographs from four different decades. These maps show that the landscape is more fragmented today than it was during its fire-suppressed period and that there is a large increase in meadow habitat.

These findings are important because an uninterrupted forest is poor habitat for many species, uses a large amount of water, and provides the conditions for devastatingly large and severe wildfires. Vegetation maps also allow me to track how water stores have changed over time. Soil moisture measurements throughout the watershed, as well as measurements from my newly installed weather stations, show that vegetation cover is closely linked with a local microclimate and soil moisture.

This link has allowed me to show that in many areas today there is likely much more water stored in the soil – sustaining plant growth and keeping streams from going dry – than there would have been without wildfires to clear out some of the trees. This increased water storage has even helped trees in the Illilouette Basin survive the recent drought.

In the winter, I switch from measuring soil moisture to measuring snow depth, which involves miles of snowshoeing in the Yosemite wilderness. I fill in depths between manual measurements using images from time-lapse cameras.

These measurements show that the snowpack is deeper in burned areas than it is in unburned forests. This is likely due to a combination of factors: snow gets caught in tree branches rather than falling to the ground, and warmer temperatures near trees compared to open areas lead to faster melting (if you’re a skier, you’ve probably noticed tree wells caused by this same kind of melting). This type of information is vital when it comes to managing California watersheds since snowpack provides most of California’s water supply.

Working on this project has been an amazing and rewarding experience. I first came to Yosemite on a week-long trip through my high school. I remember my science teacher telling us about how fire suppression was harming forests and making them more vulnerable to large fires in the long run. Ten years later, I found myself hiking through this same park, but this time with a GPS and notebook in hand, helping to increase our understanding of how fire shapes these landscapes that are so vital to providing Californians with water.