Agua Hedionda Lagoon Foundation

The Watershed

It's More Than a Lagoon, It's an Ecosystem

The 400-acre Agua Hedionda Lagoon is one of the threatened coastal wetlands on the Southern California coastline. Draining 135,000 acres in the heart of the burgeoning metropolitan area of San Diego's north county, the Lagoon watershed is a sensitive and vital ecosystem. It is home to juvenile fish, crabs, hundreds of species of marine life and waterfowl, including an array of threatened and endangered species. It is also provides a much needed respite for migrating birds. The Lagoon is unique in that it has many current uses such as a YMCA day camp, recreational boating, a mussel and abalone aquaculture facility, a white-sea bass breeding and research center and a power generating facility. The Lagoon's various usages, and the many activities and ecosystems it supports, makes it a distinctive and precious natural resource unlike any other.

Three Lagoons in One

The Lagoon extends 1.7 miles inland and is up to .5 miles wide. Three major roadbeds cross the Lagoon: Highway 101 along the coastline, the railroad and Interstate 5. These thoroughfares divide the Lagoon into 3 sections moving from the coast inland – the outer, middle and inner Lagoon. All three sections are 8-10 feet deep at their deepest part of the high tide.

Four Main Habitats

The Lagoon ecosystem consists of many different type of habitats:



Where the saltwater lagoon meets the freshwater creeks (includes both salt marsh and brackish/freshwater marsh).

Intertidal Mudflats

Intertidal Mudflats

On the edge of the lagoon, covered only at high tides.

Upland Plant Communities

Upland Plant Communities

Coastal sage scrub, mixed chaparral, grasslands and riparian.



Covered with water.

An Ever-Changing Boundary

Spring Tides, Neap Tides

Here at Agua Hedionda, freshwater creeks drain into a low-lying area meeting the sea. The ocean pushes its tides and sands against the land as the creek drains its fresh water and sediment into the sea. This mix of fresh and salt water forms a brackish environment. The salinity varies with the seasonal influence of rain and storms. We now recognize the important role tides provide in flood control, water filtration, wildlife habitat and for the unique plant communities they support.

Tides in the Lagoon ebb and flow, alternatively, twice a day. The rates of flow vary twice a month due to gravitational forces of the Sun and Moon on the Earth. When the Earth, Sun and Moon are aligned, the Moon is in its full and new phases. At this time, strong gravitational forces cause very high and very low tides. These are called spring tides (the action of the seas springing out and then springing back).

When the sun and moon are perpendicular with respect to the earth, the moon is in its quarter phases. The weaker gravitational force results in a smaller difference between high and low tides. These are called neap tides.

The essential elements to support life are in abundance: nutrient-rich mud, sunlight, and a dependable supply of oxygen- rich water from the ocean.

A Diverse System for Life

Home to many varieties of plants and animals, the Lagoon is a diverse neighborhood – look who lives and visits here:

  • Fish Icon70 species of fish
  • Reptile Icon20 species of amphibians and reptiles
  • Mammal Icon25 species of mammals
  • Bird Icon192 species of birds
  • Invertebrate Icon175 species of invertebrates
  • Plant Icon100 species of plants

And did we mention the many homo sapiens that enjoy the Lagoon's many pleasures and benefits?

Marine Life


Twice daily, the tide rises to flood the Lagoon and then ebbs, leaving much of the mudflats exposed. This constant tidal action creates a nutrient-rich environment which supports a wide variety of organisms - clams, crabs and worms live in the mud and are a food source for birds and fish.

70 species of fish live in this Lagoon. You can find flounder, white seabass, and stingrays. Look for mullet jumping several feet into the air and moving into shallow water to spawn.

Birds Tell Us a Lot

Birds provide us a glimpse of the diversity of life that depends on the Lagoon. Birds are indicators of the ecological health of the area. Whether they are soaring overhead, cruising by in formation, or scurrying into the underbrush, each species occupies a unique niche in the ecosystem.

The surrounding habitats support many birds which are endangered or threatened with extinction. Other species which are not endangered, but which are experiencing a serious decline in population, also live here.

Who's flying by? Look for California Brown Pelican gliding over the Lagoon, California towhees feeding in the understory, the red-tailed hawk hunting from high above, and Anna's hummingbirds defending their territory. Urbanized birds comfortable in a urban setting are also abundant: American crows, house finches, house sparrows, northern mockingbirds, mourning doves, rock doves (pigeons) and European starlings.

California Brown Pelican Northern Harrier Western Snowy Plover