Sri Sangkawati, Iwan K. Hadihardaja, J. Hadihardaja
When the water is polluted, it can be improved by diluting the degradated water with the higher quality water. Supply of water dilution trigger several costs, as the cost to build reservoir for water discharge. The clasification of project in river basin is appropriate with the benefit, there are single purpose and multi purposes project, so in relation to water discharge as dilution, it needs cost sharing with other beneficiaries. The cost sharing of BJP-SDA with the case study on Brantas River basin is determined with Analytic Hierarchy Process (AHP) with Expert Choice 2000. The charge percentage of BJP-SDA toward the cost is recovered with three criteria, those are the raw water (domestic and industry) 28.4% ; hydropower 28.8% ; irrigation 27.9% ; flood control 12.5% and to improve the water quality 2.3%. The charge percentage of BJD-SDA toward the cost is recovered with four criterias, they are: the raw water 26.10%; hydropower 32.7%; irrigation 27.7% ; flood control 11,3% and to improvement of the water quality 2.2%. With the allocation of river water for dilution is 7.5 m3 /sec during three months on dry season, BJP-SDA charge to improve the water quality in Brantas River has the lowest, that is, 2.2 – 2.3% from the cost which will be covered. Under the O and M cost, the percentage of the BJP-SDA charge is 0.8% and under the benefit value of the user is 1.7% from the cost which will be covered. The water pricing of BJP-SDA for the beneficiaries of the river water quality improvement is the water allocation for dilution divides with the cost which will be covered. For the O and M cost recovery, the water price is Rp. 112 until Rp. 117 per m3, and for the full cost recovery is Rp. 126 until Rp. 132 per m3.