The Department on behalf of the State of Illinois shall devise and develop a continuing program for the apportionment of water to be diverted from Lake Michigan among regional organizations, municipalities, political subdivisions, agencies or instrumentalities for domestic purposes or for direct diversion into the Sanitary and Ship Canal to maintain such canal in a reasonably satisfactory sanitary condition; provided, however, that in developing the continuing program and in making allocations, the amount used for discretionary dilution for water quality purposes in the Sanitary and Ship Canal shall not exceed an annual average of 320 cubic feet per second and the Department shall not allocate less than 320 cubic feet per second for discretionary dilution before October 1, 2000, without conducting a hearing initiated after notification from the Illinois Environmental Protection Agency of the completion or improvement of waste water treatment facilities or change in standards that affect water quality. In addition to the other requirements of this Act, the Department shall give priority to allocations for domestic purposes in making allocations to new users of Lake Michigan water, and shall to the extent practicable make any allocations to new users of Lake Michigan water with the goal of reducing withdrawals from the Cambrian-Ordovician aquifer. The Department shall also follow these provisions in developing its continuing program. The Lake Michigan water so diverted, whether by way of pumpage for domestic purposes from the lake the sewage effluent derived from which reaches The Illinois Waterway, or by way of storm runoff from the Lake Michigan watershed which is diverted into the Sanitary and Ship Canal, or by way of direct diversion from the lake into the canal, shall not exceed a 40 year running average of 3,200 cubic feet per second and shall not exceed 3,680 cubic feet per second in any annual accounting period except that in any two annual accounting periods within a 40 year period the average annual diversion may not exceed 3,840 cubic feet per second as a result of extreme hydrologic conditions. The program, which shall be published, shall be developed in cooperation with local governmental agencies and other interests; in the development of the program and rules and regulations the Department is authorized to hold public hearings to gather information related thereto.