CA Water Code Section 31336

A district may invest such surplus money, as its board deems wise or expedient in any of the following:

(a)

Bonds issued by the district.

(b)

Bonds issued by any school district any part of which is in a county containing any part of the county water district.

(c)

Bonds issued by the State.

(d)

Bonds issued by the United States.

(e)

Registered warrants issued by the State.