Once a deep bay, now a vital estuary. Welcome to Los Peñasquitos Marsh Natural Preserve. This 574-acre preserve evolved from a river valley into what you see today a haven for wildlife and a testament to nature’s resilience.
The name “Los Peñasquitos” means “The Little Cliffs” in Spanish. It hints at the landscape surrounding this unique marsh. Over time it has also been called Cordero Slough, Soledad Lagoon, Torrey Pines Lagoon and Sorrento Lagoon.
Los Peñasquitos Lagoon is a border. It divides a colony of the endangered Torrey pine. Three streams converge here Carroll Creek, Carmel Creek, and Los Peñasquitos Creek. Together they drain a 95-square-mile basin. Los Peñasquitos Creek has the largest drainage area making up 70% of the total. Historically, these streams were seasonal. Urbanization changed that. Irrigation runoff now keeps them flowing year-round.
Imagine this lagoon thousands of years ago. Around 6000 years Before Present, the sea level rose transforming this area into a deep bay. About 4000 years Before Present, sediment began to accumulate creating sandy beaches. By 3600 years Before Present, it transitioned into a brackish marsh. Around 2800 years Before Present, it finally became the salt marsh we recognize today.
Centuries ago, the Kumeyaay tribe thrived here. As early as 6000 Before Present, they harvested scallops, clams, and oysters. Their village, Ystagua, stood in Sorrento Valley. Today, archeological sites around the lagoon whisper stories of their past.
In the 19th century, Rancho Los Peñasquitos became the first land grant in San Diego County. The valley was used for crops. Later, a railroad line cut through the eastern part of the area. It transported construction materials to pave San Diego’s streets.
Transportation links now intersect Los Peñasquitos Lagoon. Highway 101 runs along the western edge. A Santa Fe Railroad line crosses in the center. Interstate 5 lies to the east. These routes have shaped and altered the lagoon’s ecosystem.
The Santa Fe Railroad built a causeway in 1925. This embankment restricted the lagoon’s natural drainage. It changed the tidal flow. Today, Coaster and Pacific Surfliner trains still use this route.
In the 1930s, the Pacific Coast Highway was expanded. A bridge was built over the lagoon’s mouth. Its wooden pilings often clogged with sand disrupting the water flow.
For years, wastewater treatment plants pumped effluent into the lagoon. This affected the water quality and ecosystem. Pump Station 64 had frequent spills releasing millions of gallons of raw sewage into the lagoon. While improvements have been made spills still occur.
Recognizing the lagoon’s importance, the California Division of Parks and Recreation designated Los Peñasquitos Lagoon as a State Preserve. This gives it greater protection. Public access is limited preserving its fragile ecosystem. In 1987, 240 acres of marshland were added to the parkland purchased from SDG&E. SDG&E had considered the site for a nuclear power plant but never built it.
To address human-caused problems, the Los Peñasquitos Lagoon Enhancement Plan was created in 1985. This plan monitors water quality, manages sand removal, and coordinates with agencies to protect and restore the lagoon. The Los Peñasquitos Lagoon Foundation implements this plan.
The lagoon’s mouth is periodically breached to improve water quality and regulate water levels. This helps reduce the risk of diseases like West Nile virus. Closures often occur due to winter waves.
In 2005, a new bridge was built over the lagoon’s mouth replacing 72 pilings with just four. This improved water flow.
Several trails offer views of the marsh. The Marsh Trail skirts the southern edge. The Del Mar trail follows the railroad causeway. These trails allow us to appreciate the beauty of Los Peñasquitos Lagoon.
However, dangers exist. Mosquitoes can carry West Nile virus. Rattlesnakes are also present. Mountain lions though rare may pass through.
Los Peñasquitos Lagoon faces threats of increased salinity, sedimentation, and freshwater runoff. Restoration efforts aim to keep the inlet open, create new flow channels, remove deposits, and reduce pollution.
Los Peñasquitos Lagoon stands as a reminder of the delicate balance between nature and human activity. It is a place to cherish for generations to come.