An appropriation shall be immediately available for encumbrance or expenditure during the period specified therein, or, if not otherwise limited by law, for three years after the date upon which it first became available for encumbrance or expenditure. An appropriation containing the term “without regard to fiscal years” shall be available for encumbrance from year to year until expended.

An appropriation shall be deemed to be encumbered at the time and to the extent that a valid obligation against the appropriation is created. However, a state agency may estimate encumbrances consistent with the authority of the appropriation, and may make corrections or adjustments to any encumbrance or estimated encumbrance during the liquidation period described in Section

16304.1.

As used in this code and in every other statute heretofore or hereafter enacted, the term “unexpended balance” shall be construed to mean “unencumbered balance.”

Appropriations for the following purposes are exempt from limitations as to period of availability in any appropriation, and shall remain available from year to year until expended:

to, the Architecture Revolving Fund and the Water Resources Revolving Fund.

state.