Cal. Public Utilities Code § 12871

A district may invest any surplus money in its treasury, including money in any sinking fund, in any of the following: (a) Its own bonds, whether issued on behalf of the entire district or any special district. (b) Treasury notes, certificates of indebtedness, bills, bonds of the United States, or any other evidence of indebtedness secured by the full faith and credit of the United States. (c) Obligations issued pursuant to the Federal Home Loan Bank Act or the National Housing Act. (d) Treasury notes or bonds of this state, or of any public corporation, municipal corporation, public district, or political subdivision within this state which are legal as security for the deposit of public funds. (e) Obligations issued by federal intermediate credit banks, federal land banks, and banks for cooperatives. (f) Obligations issued or assumed by the International Bank for Reconstruction and Development, the Tennessee Valley Authority, the Inter-American Development Bank, or Export-Import Bank of Washington participation certificates. (g) Banker’s acceptances of banks having total deposits of one billion dollars ($1,000,000,000) or more. (h) Any securities in which savings banks in this state may legally invest their funds pursuant to Sections 1350 to 1366, inclusive, of the Financial Code; provided, that the provisions of said sections limiting the amount which a savings bank may invest in securities to a specified percent of its paid-up capital and surplus, or savings deposits, shall not apply to investments authorized by the terms of this section.