Water
Creeks, watershed
Harvard Way is the boundary of the El Dorado Hills watershed. North of Harvard Way, the creeks drain to the American River and Folsom Lake. Two of these include New York Creek and Deer Creek. South of Harvard Way, creeks drain to the Cosumnes River. These include Carson Creek and Dusty Creek.

Water supply
Paolo Sioli, one of the early historians of El Dorado County, describes the location of three canals that supplied much of the fresh water needs of western El Dorado county in the late 19th century:
- A canal running along an east-west ridge from the junction of the North and South forks of the American River
- A canal running west from the mouth of Weber Creek
- A canal running west through the plains between the South Fork of the American River and the Cosumnes River
Ranchers living along the western slope also dug wells to supply their own needs and the needs of their animals, gardens, and crops.
However, although the wells supplied enough water for some of the residents’ needs, they often fell short when it came to emergencies. Madeleine Petersen Moseley, a 20th century El Dorado Hills area pioneer, described how lack of water for fire fighting caused an exodus from the western slope. Moseley’s family home burned to the ground when a spark started a blaze that couldn’t be extinguished by available local water, and the response time for the nearest firefighters, located near Camino, was about 4 hours.
Today, water for El Dorado Hills is supplied by the El Dorado Irrigation District (EID), a public agency serving central and western El Dorado County.