Okla. Stat. tit. 19 § 957-1
The county commissioners of any county establishing a drainage district or districts, and establishing a county retirement system, in addition to the duties and authority now provided by law, are hereby authorized to pay into the retirement system of such county for the use and benefit of the employees eligible for retirement benefits, such amounts as the board of county commissioners may authorize by resolution not exceeding the current annual salaries of all employees whose salaries are paid either in whole or in part out of the drainage district funds. The total employer and employee contributions shall not exceed the percentages of the monthly compensation of each member set forth in Section 954 of this title.
Okla. Stat. tit. 19, § 957-1