Lake Lagunita - Stanford University EarthCache

Welcome to Stanford University

At the edge of of Stanford University lies Lake Lagunita, a quiet, seasonal basin that hints at a dynamic interplay between climate, geology, and water. This EarthCache invites you to explore why this man-made lake, often empty during the summer, plays a meaningful role in understanding hydrology, percolation, and the future of water in California’s changing climate.

The Story Behind Lake Lagunita

Lake Lagunita was originally constructed in the late 1800s to serve as a stock pond for horses, but its role has changed dramatically over time. Today, it functions as a seasonal wetland, a site for ecological research, and a visible example of how climate, geology, and water management interact in a Mediterranean climate like that of coastal California. Though the lake once filled more reliably, it is now dry for much of the year.

The lake sits within the San Francisquito Creek watershed, a system that channels rainfall and runoff from the eastern slopes of the Santa Cruz Mountains toward the San Francisco Bay. This watershed includes both natural and engineered features such as dams, reservoirs, storm drains, and underground aquifers. Lake Lagunita is not connected to a consistent flowing stream. Instead, it relies on three main sources of water: direct precipitation, runoff from nearby hills and urban surfaces, and intermittent diversions from nearby reservoirs or creeks like Felt Reservoir and San Francisquito Creek.

The underlying geology is key to understanding how the lake functions. Beneath the lakebed are layers of sand, gravel, and clay, which influence how water moves through the soil. Sand and gravel allow water to seep downward easily, while clay acts as a slower barrier. This stratified structure means that when water enters Lake Lagunita, it does not stay on the surface for long. Instead, much of it percolates through the porous basin and recharges underground aquifers. This natural infiltration process helps supply water for trees, landscaping, and wells across Stanford’s campus, reducing reliance on imported water.

Another major factor that influences the lake is evapotranspiration, which includes both evaporation from the water’s surface and transpiration from plants. Native and invasive vegetation surrounding the lake can significantly increase water loss, especially during California’s hot, dry summers. Even in wetter years, these processes make it difficult for surface water to remain in the basin for long.

In recent decades, climate change has added a new layer of complexity. Warmer average temperatures, longer dry seasons, and more unpredictable rainfall patterns have all reduced the reliability of winter and spring precipitation. With less consistent watershed input and higher evaporation rates, Lake Lagunita now fills less often and dries out more quickly than it once did. These trends are expected to continue, making the lake an indicator of regional hydrologic stress.

Despite often appearing dry or inactive, Lake Lagunita remains a valuable outdoor classroom. It allows scientists, students, and visitors to observe natural hydrologic processes such as infiltration, surface runoff, water cycling, and seasonal variability. The lake also supports limited wetland habitat for birds and amphibians during wetter years. As a case study in how changing climate and land use affect local water resources, Lake Lagunita plays an important role in environmental education and sustainability research at Stanford and throughout the Bay Area.

Tasks for This EarthCache

To log this EarthCache, visit the location and complete the following tasks. Send your answers via Geocaching or email.

1. Include “Lake Lagunita - Stanford University - GCB98A2” on the first line of your message.

2. Describe the condition of the lake at the time of your visit. Is it dry, muddy, partially filled, or holding significant water? What does this tell you about the recent weather or season?

3. Look at the soil and surrounding vegetation. Based on what you observe, how might water be entering or leaving the lake?

4. Examine the surrounding topography. What features nearby help guide water into the basin?

5. Based on what you’ve learned, why do you think Lake Lagunita does not hold water year round? Include at least one natural and one human factor.

6. In your log, attach a photo of yourself or a personal item with Lake Lagunita in the background. (Note: photos predating the publication of this EarthCache are not accepted.)