Cal. Wat. Code § 35454
If the available water is inadequate to serve all of the land as to which applications for water are filed pursuant to Section 35450, the district may require the owners of land which is proposed to be planted to annual crops or to new plantings to take a proportionate percentage reduction in the water they would normally use thereon and may require the owners of land which is planted to permanent crops to take a reasonable proportionate percentage reduction in the water they would normally use in an amount not exceeding the percentage reduction required of plantings to annual crops and new plantings.
The provisions of this section shall be effective only if more than one-half of the district's revenue for that year will be derived from charges made for the sale of water.
Ca. Water Code § 35454