User:Strawberry.creek/San Andreas Creek

Watershed
San Andreas Creek's source elevation is at approximately 900 feet (270 m) on the eastern slopes of Sweeney Ridge from which it flows southeasterly along the San Andreas Rift between Sweeney Ridge to the west and Buri Buri Ridge to the east, through San Andreas Reservoir, which was formed by the construction of a 100-foot-high (30 m) earth dam in 1868. The San Andreas Dam eliminates flow in the creek immediately below the dams, except for occasional spills or releases from the reservoir and seepage through the dam. From San Andreas Reservoir, the creek descends and enters the northeast arm of Lower Crystal Springs Reservoir. Historically San Andreas Creek joined San Mateo Creek just above the current location of the Crystal Springs Dam. The two Crystal Springs lakes and San Andreas Lake used to be known as Spring Valley Lakes for the Spring Valley Water Company, which owned them. Lower Crystal Springs Reservoir now covers the town of Crystal Springs, which grew up around a resort of the same name.

Before European settlers arrived, much of the San Andreas Valley portion of the watershed was composed of wetlands. Wetlands are habitats that are a combination water-submerged land, and land that floats above the water. They have several different categories, which are distinguished by the type of water (freshwater, saltwater, etc.) and the type of land (marshes, mangroves, etc). San Andreas Creek was lined with several, relatively small sag ponds, which are bodies of water formed by fault line movements that create basins where freshwater can collect. These aquatic habitats allowed riparian (referring to the banks of bodies of water) wildlife to thrive. However, the arrival of colonizers between the late 18th and mid 20th centuries led to a string of impactful environmental and ecological changes to San Andreas Creek and the rest of the watershed. For instance, several dams were built, including the San Andreas Dam, and the Upper and Lower Crystal Springs Dams. These dams completely deluged the naturally existing aquatic habitats, including the riparian ones, desiccating much of the wildlife. However, for a period of time before the 20th century, the existing grassland habitats seemed to increase, while shrubland area decreased, as a result of the farming practices introduced by the Spanish, and the forced termination of Indigenous burning practices. However, modern American influences from the mid 20th century onwards have decreased the grassland area by about 70%, and this destruction was accelerated by highway construction and residential development. These haven't been the only habitats to face destruction around the San Andreas creek and the surrounding area; furthermore, other environmental damages, such as Sudden Oak Death and the spread of plant pathogens, have exacerbate as a result of various human-created developments. In response, there have been efforts to restore several original habitats, including wetlands, grasslands, and others.