CA Gov't Code Section 65040.4

(a)

The office shall divide the state into regional planning districts. Insofar as possible, the districts shall be established to include:

(1)

Natural physiographical regions containing complete watersheds of major streams, and the land upon which the waters of such watersheds are put to beneficial use.

(2)

Areas having mutual, social, environmental, and commercial interests as exemplified by connecting routes of transportation, by trade and by common use of open space and recreation areas within the region.

(b)

The regional planning districts established by the Council on Intergovernmental Relations pursuant to former Section 34216 shall remain in effect as the regional planning districts of the office until changed by the office.