Cal. Water Code § 13833

The department shall require the payment of interest on each loan that is made pursuant to this chapter at a rate equal to the average, as determined by the Treasurer, of the net interest cost to the state on the sales of general obligation bonds pursuant to this chapter. However, when the applicable average of the net interest costs to the state is not a multiple of one-tenth of 1 percent, the interest rate shall be at the multiple of one-tenth of 1 percent next above the applicable average of the net interest costs.