Cal. Wat. Code § 51681
Parcels purchased at delinquent sale by the county treasurer as trustee for the district shall be offered for sale within three years from the expiration of the redemption period, or before October 1, 1951, whichever period is greater, in parcels of such number of acres as the board may determine will be most desirable for purposes of assuring the sale thereof.
However, such parcels may be retained by the county treasurer as trustee for the district beyond such time so long as the district annually, with respect to such parcels, pays to the county in which such parcels are situated an amount equivalent to taxes levied by such county on similar parcels similarly situated in the county in the same manner as provided in the Revenue and Taxation Code for secured property tax payments.
Ca. Water Code § 51681