California Code, Water Code - WAT § 11840

All money in the construction fund not required to meet preconstruction, acquisition, or construction costs and expenses, or interest thereon, of the project, or unit thereof, for which bonds were issued and sold, and all funds constituting surplus revenues which are not immediately needed for the particular object or purpose to which they are required to be applied or are pledged shall be invested in bonds and obligations eligible for investment of surplus State money.