Cal. Water Code § 2802

In determining rights based on an incomplete appropriation initiated according to law prior to December 19, 1914, and since prosecuted with reasonable diligence in accordance with Section 1416 of the Civil Code, the board shall prescribe such reasonable time for the completion of the appropriation and the application of the water to a beneficial use as will enable the claimant acting in good faith and with due diligence to complete the appropriation.