Americano Creek - Environmental Factors

Environmental Factors

California's 1994 water quality report designated all of Americano Creek and most of the Estero Americano as "impaired" streamways as defined in section 303(d) of the Federal Water Resource Statutes, due to runoff from pasture land and feedlots. As recently as 1987, a single gully near Americano Creek released 4,000 tons/year of sediment, contributing to flooding in downstream communities and making the creek non-navigable. Pollutants found at hazardous level in the creek have included fecal bacteria, copper, ammonia, and zinc.

The creek's headwaters area is a historic habitat for a number of rare and endangered species including Sebastopol Meadowfoam, Limnanthes vinculans; Showy Indian clover, Trifolium amoenum; and Pitkin Marsh lily, Lilium pardolinum ssp pitkinese. This area also contains a closed landfill, and as of 2006, a hard rock quarry was proposed for it.

Americano Creek is dry 4 to 6 months each year. For its first 8 mi (13 km), the stream meanders through a broad valley dominated by agricultural uses, principally cattle grazing. The valley floor is flat and wide, especially at the lower elevations. Due to siltation, virtually no rocks are evident in the streambed. Grazing occurs in the streambed itself, putting pathogens directly into the water. During the rainy season (November to April), this bottomland consists in places of an expansive marshy area. Most native wetland vegetation has been destroyed by ongoing grazing. Grazing is so intense that cattle are seen wading in a broad marshy streambed over 16 in (40 cm) deep and over 300 ft (100 m) wide.

The lower reach of Americano Creek is also surrounded by agricultural uses. However, the channel becomes better separated from grazing areas. The Estero itself is a Federally-protected area.

Flow rates are highly seasonal with the heaviest flows occurring in the rainy winter months. Water testing of Americano Creek and the Estero has generally found pH (acidity) levels in the range of 7.5 to 8.0, which satisfies the guidelines in the State of California Basin Plan.

In some years, a sand bar forms at the mouth of the Estero, restricting tidal exchange. At other times, tidal influences extend up to 4 miles (6 km) from the mouth. High levels of salinity have been observed in the Estero.

The Estero Americano is protected by the Estero Americano State Marine Recreational Management Area. Like an underwater park, this marine protected area helps conserve ocean wildlife and marine ecosystems.