The Santa Ynez Indian Reservation is situated above a bedrock ridge that forms the southern boundary of the Santa Ynez upland ground-water basin. A pumping depression exists upgradient from the reservation, and water levels have declined an average of 1.0 to 1.5 feet per year since the 1940's. This decline in the water level has led to the cessation of perennial flow in Zanja de Cota Creek that traverses the reservation. In the past this creek was fed by the natural discharge of water from the ground-water basin. Water-bearing rock beneath the reservation is limited in thickness and may become unusable as a water supply source in the near future if water levels continue to decline.
The chemical quality of water beneath the reservation is generally acceptable for both irrigation and domestic use; however, large-scale pumping could induce the flow of contaminated water from an area just upgradient.
Declines in ground-water levels and the existence of fecal contamination upgradient from the reservation make the successful development of a groundwater supply for the reservation doubtful.
