The California Office of Environmental Health Hazard Assessment has issued a safe eating advisory for any fish caught in Laguna de Santa Rosa due to elevated levels of mercury and PCBs.

The sinuous watercourse and associated wetlands form a significant floodplain during the heavy winter rains, capable of storing over 80,000 acre-feet (99,000,000 m3) of stormwater.

[7] Notwithstanding the large historical reduction in resource extent, the Laguna de Santa Rosa is presently the second-largest freshwater wetland in coastal Northern California and still habitat to over 200 species of birds, threatened and endangered salmonid species, bald and golden eagle, osprey, mountain lion, river otter, coyote, bobcat, mink, and gray fox.

While the Laguna has been heavily impacted by human activities in its watershed over the past century, in recent years a movement has grown to preserve and restore it both for ecological functions such as habitat values and flood control capacity, and for outdoor recreation, education, and research.

The principal source of the Laguna de Santa Rosa lies in the hills on the east side of U.S. Route 101 near Cotati, California.

It flows under the Old Redwood Highway just south of Charles Street and joins with a drainage channel near the end of Marsh Way.

Their northern border was about two miles (3 km) north of present-day Healdsburg, and included the lower portion of Dry Creek.

(Note: The above paragraphs are based on the work of David A. Fredrickson, Ph.D. and Daniel W. Markwyn, Ph.D.) The ancient Laguna of 2000 BC supported these tribes with abundant fish, fowl and tule reeds for constructing homes and canoes.

By the 1960s, encroachment of the vast eastern plain was almost complete, and the previously rich run of 1.6 million anadromous fish had virtually collapsed.

By 1989 over 92 percent of the Laguna's historic riparian habitat had been lost, and its water quality had reached critically poor levels.

In that year the Laguna de Santa Rosa Foundation was formed to mobilize public and private resources for preservation and restoration of this natural area.

Around 12 million years ago, processes of uplift and volcanic action formed the Mayacamas and Sonoma Mountains to the east and established the main geomorphic features of the present day landscape.

As an element of the Pacific Flyway, the Laguna is home to a large variety of avifauna including Ridgway's rail, Canada goose (Branta canadensis), turkey vulture (Cathartes aura), black-necked stilt (Himantopus mexicanus), burrowing owl (Athene cunicularia), great egret (Casmerodius albus), great blue heron (Ardea herodias) and American kestrel (Falco sparverius).

At the federal level, the U.S. Army Corps of Engineers has played a role in analysis of water quality, especially related to sediment issues, and the National Marine Fisheries Service of the National Oceanographic and Atmospheric Administration regulates critical habitat and recovery efforts for threatened and endangered salmonid species.

Locally, the Sonoma County Water Agency manages areas of the Laguna for flood control, and the City of Santa Rosa's Subregional wastewater System's main plant is located in the Laguna floodplain and owns and manages adjacent lands for storage and agricultural reuse of treated wastewater as well as for habitat values.