Each accredited public library system shall receive an annual allocation of state funds to supplement the local appropriation and other income. Library cooperatives which include accredited public library systems may receive state aid. The state aid shall be used only to support library services in accredited public library systems and in cooperatives including accredited public library systems. The amount of the minimum allocation for each public library system shall be based on specific local service levels of the public library system and as identified by accreditation category.