Permanente Watershed

Permanente Creek drains a watershed of approximately 17.5 square miles on the northeast-facing slopes of the Santa Cruz Mountains. The headwaters originate near Black Mountain along the Montebello Ridge.  The mainstem flows east through unincorporated County land for about five miles, then turns to the north at the base of the foothills and continues another eight miles along the valley floor traversing through the cities of Los Altos and Mountain View, finally draining to the Lower South San Francisco Bay.   The major tributaries are the West Branch Permanente Creek and Hale Creek. 

Unlike most watersheds in the Santa Clara Basin, the headwaters of the mainstem are not protected as open space, but are developed for light industry and mining.  Only the headwaters of the West Branch Permanente Creek are protected as open space by the Mid Peninsula Open Space District.  The majority of the watershed downstream of this tributary confluence is developed as high-density residential neighborhoods, with commercial development clustered along major surface streets such as El Camino Real.  Some heavy industry is clustered adjacent to Highway 101 in the lower watershed by the Bay.

Stream flows are typically perennial in the upper watershed areas and ephemeral in the valley floor, with the exception of Hale Creek, which typically has minimal flow throughout the summer season.  The hydrology of the watershed has been significantly altered to provide greater flood protection.  The Permanente Creek Diversion, constructed in 1959, and located about 1.5 miles upstream of Hale Creek confluence, currently diverts stream flows up to 1,500 cfs into Stevens Creek during the winter season (SCBWMI 2001).  Permanente Creek is also diverted at the mouth from Charleston Slough eastward to Mountain View Slough (SCVWD 2004).

Watershed Facts

  • Drainage area:  17.3 square miles
  • Number of creeks:  7
  • Miles of creek:
  • Miles of Engineered Channel:
  • Miles of Underground Culvert or Stormdrain:
  • Local jurisdictions:  Santa Clara County, Palo Alto, Los Altos, Mountain View
  • Percent area by land use:
    • Residential 46.3%
    • Industrial/Commercial 13.1%
    • Forest 35.0%
    • Rangeland 2.8%
    • Other 2.8%
  • Percent Impervious Area:  43.9%
  • Beneficial Uses:  COLD, SPWN, WILD, REC-1, REC-2

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