AN ASSESSMENT OF SPRING HYDROLOGY IN THE MT. LAGUNA AREA OF THE CLEVELAND NATIONAL FOREST

Mt. Laguna is a popular location for recreation and home to a small residential community on the eastern edge of the Cleveland National Forest, only 55 miles from downtown San Diego. Despite the significance of water availability to the sustenance of this important region, records of the location and flow of springs in the area are largely sparse and out of date. Some historical spring locations and flow rates are available from records of academic research and water rights claims from during the twentieth century; however, no comprehensive assessment of these resources has been completed since. This is of particular concern, as the complex nature of groundwater storage on Mt. Laguna makes it difficult to generalize about the area’s water availability. As concerns surrounding fire management and water availability have grown as drought conditions in Southern California have continued to become more prevalent over the last few decades, the importance of fully understanding the availability of water resources on Mt. Laguna and how they are changing through time has also grown. Consequently, this project undertook a formal investigation into the state of spring-based water resources on Mt. Laguna, consisting primarily of aerial surveying and fieldwork to locate and evaluate the presence and flow of springs on the mountain today in tandem with a review of historical documents, including well records and geologic maps, to provide a historical context to this information. Preliminary results indicate that overall flow rates of springs on Mt. Laguna have decreased substantially. For instance, one particularly well-documented spring recorded an average discharge of 60.42 L/s between 1974 and 1976, but only 0.98 L/s in summer 2021. Further research is continuing to investigate remaining questions, including whether this decrease in flow rate is uniform or varied, what exactly groundwater availability on Mt. Laguna looks like today, how this compares to historical water resources, and how this may change in the coming decades. Continual work in the improved documentation of the presence and flow of springs on Mt. Laguna is one important step in helping to shape a more comprehensive view on the state of water in the area and help to guide effective management of this valuable resource.