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Dams, Development and Displacement: Rephotographing the Peninsula Watershed

Sep 12 2018

 

After carefully lining up a historical shot of Pilarcitos Reservoir, I began capturing photos of the present-day landscape. To the right is Jim Avant, an SFPUC Watershed Keeper, who's knowledge of the area was invaluable in the field.  
 

By Nick Mascarello
B.S. Earth Systems '18
Resilient Landscapes Intern, San Francisco Estuary Institute

Out West Student Blog

Student Blog

Just west of Interstate 280 sits something that San Francisco and many nearby cities depend upon each and every day. Without it, it’s a safe bet that the region would never have transformed into what it is today. Nestled among the Santa Cruz Mountains is a network of dams, flumes and tunnels operated by the San Francisco Public Utilities Commission (SFPUC) that provides water to customers up and down the San Francisco Peninsula. Since the rapid development of the region beginning in the 1850s, many of the peninsula’s hydrological features have been significantly altered. From diversions redirecting water to massive dams holding back the lakes visible from I-280, the watershed bears little resemblance to what it once was.

From diversions redirecting water to massive dams holding back the lakes visible from I-280, the watershed bears little resemblance to what it once was.

Currently, the San Francisco Estuary Institute (SFEI), the organization I’ve worked with this summer, is in the midst of a dive into the historical ecology of this modified landscape – the Peninsula Watershed. Commissioned by the SFPUC, a hallmark of the study is the synthesis of historical information and reconstruction of historical environmental conditions. This process will ultimately shed light on ecosystem disruptions spurred by land use change and development throughout the watershed. A critical piece of the project concerns the shifts in plant communities over the last century and a half. Earlier this summer, I geolocated a number of historical photos from throughout the watershed in GIS, essentially mapping out the points where each shot was likely taken from. Recently, I built on this by recreating many of the historical photos over three field days.

Each attempt at capturing a rephotograph presented unique challenges. To line up each shot, my colleagues and I referenced a print out of the map I had created in GIS, ensuring that we were as close to the photo’s corresponding point as possible. Then, we turned to the historical image and aligned it to the landscape before attaching the camera to a tripod and capturing the shot. Some were relatively easy to line up, particularly images clearly showing the watershed’s infrastructure. Others weren’t so easy. Photo three (see collage) was tricky to line up because of the vegetation that has grown in around the dam. Photo two, captured on the eastern shore of Crystal Springs Reservoir, even required a boat ride across the lake!

A side-by-side comparison of three historical images and their modern counterparts.

Three of the historical images that were successfully recreated, side by side with their modern counterparts. Courtesy of the San Francisco Public Utilities Commission
Click to enlarge

To line up each shot, my colleagues and I referenced a print out of the map I had created in GIS, ensuring that we were as close to the photo’s corresponding point as possible. Then, we turned to the historical image and aligned it to the landscape before attaching the camera to a tripod and capturing the shot.

While I hadn’t expected my internship to include landscape photography, let alone rephotography of hundred plus year old pictures, my work proved worthwhile. SFEI will utilize these new photos to assess change in vegetation communities within the watershed. The photos above illustrate just a few of the trends that I saw in the field, especially the displacement of grassland communities and clear expansion of forest ecosystems. I was surprised by the clarity of vegetation change and I’ve come to recognize the value of rephotography as tool to analyze environmental change through time by contributing to this project.

Through my work at SFEI, I had the opportunity to a step back from many of the more precise environmental topics that I studied as an undergraduate. Instead, I’ve more broadly considered the story of long-term change and human influence throughout the Peninsula Watershed, working with my colleagues to uncover its environmental history. I hope to further explore this sort of environmental research as a graduate student and beyond as I pursue a career rooted in conservation.

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