The Petaluma River is a river in the California counties of Sonoma and Marin that becomes a tidal slough for the majority of its length. The headwaters are in the area southwest of Cotati, the word Petaluma may derive from the Miwok words pe’ta, flat, and luma, back. The Miwok people lived in Sonoma County for more than 2500 years, Petaluma was the name of a village on a low hill east of Petaluma creek and north east of the present day town of Petaluma. The first recorded exploration of the Petaluma River was by Captain Fernando Quiros in October,1776, located in southern Sonoma County, California, and a portion of northeastern Marin, the Petaluma River Watershed drains 146 square miles. The watershed is approximately 19 miles long and 13 miles wide with the City of Petaluma near its center, the lower 12 miles of the Petaluma River flow through the Petaluma Marsh, the largest remaining salt marsh in San Pablo Bay. The marsh covers 5,000 acres and is surrounded by approximately 7,000 acres of reclaimed wetlands, in the marshes west of Lakeville, the river is joined by San Antonio Creek, at which point it becomes the boundary between Marin County and Sonoma County. The river flows under State Route 37 at Green Point and enters northwest San Pablo Bay just north of Petaluma Point, while the rivers source lies over 300 ft above sea level, it descends to 50 ft within about 0.4 mi. The river is fully tidal 11 mi from its mouth, indicating its slight gradient through the marshes below Petaluma, the United States Army Corps of Engineers dredges this section to keep it navigable by gravel barges and pleasure craft. The Petaluma River Watershed hosts several federally endangered animals including the salt marsh harvest mouse, endangered flora include soft bird’s-beak, Baker’s stickyseed, Burke’s goldfields, showy Indian clover, and Sebastopol meadowfoam. Steelhead that spawn and rear in the Petaluma River watershed are wild, not hatchery, Chinook salmon are seen in the main stem of the Petaluma River and The United Anglers of Casa Grande High School have seen chinook at the turning basin, near the Lynch Creek confluence. The high school constructed a salmonid hatchery in 1993 and in 200274 Chinook salmon returned to spawn in the Adobe Creek tributary. The marshes provide an important wildlife habitat and fish hatchery, however, since the onset of intensive immigration in the mid-1850s, the water quality has diminished, partly due to overgrazing and other agricultural uses. Pollutants present in the river include nitrates, phosphates, petroleum hydrocarbons, pesticides, urban runoff, particularly from the City of Petaluma, adds heavy metals and hydrocarbons to the river. Starting about 1990, material steps were taken to mitigate the pollution, because the Petaluma River is relatively well-protected, most of the pollution comes from nearby storm drains. It is up to the people of Petaluma to keep the river clean, because most of the length of the waterway is tidal and urban/suburban, there is a significant collection of tidally deposited debris along the banks. Despite the poor aesthetics including turbidity, the quality is not particularly poor. It has been alleged that the greatest threat to the Petaluma River is the planned Dutra asphalt plant, the reported concerns involve the loud noises it will create that will scare away the birds and throw off the entire ecosystem. The longest highway span, the 4-lane Route 37 bridge, is 2,183 ft long and was built in 1958, the oldest public bridge, built in 1925, is a 114 ft concrete triple span carrying two lanes of Petaluma Boulevard North
The river flowing through Petaluma. View is to the southeast.
The mouth of the Petaluma River on San Pablo Bay. View is to the northeast.
Petaluma River Watershed 2007 Steelhead Trout Biosurvey