Unless otherwise provided by law all moneys which may from time to time be appropriated out of the State Treasury for the use of soil and water conservation districts shall be available to pay the administrative and other expenses of such districts and shall be allocated by the department among the districts already organized and to be organized during the fiscal year for which such appropriation is made. Such allocation shall be fair, reasonable and in the public interest, giving due consideration to the greater relative expense of carrying on operations within the particular districts because of such factors as unusual topography, unusual severity of erosion, special difficulty of carrying on operations, special volume of work to be done and the special importance of instituting erosion control and soil and water conservation operations immediately. In making allocations of such moneys, the department shall reserve an amount estimated by it to be adequate to enable it to make subsequent allocations in accordance with the provisions of this section from time to time among districts which may be organized within the current fiscal year after the initial allocations are made. All appropriations made for the purpose of this chapter shall be disbursed by the State Treasurer on warrants approved and signed by the department.