A regional wholesale water supplier shall reimburse the state for all costs incurred by the State Department of Public Health or the Seismic Safety Commission in carrying out the duties imposed by this division. The bay area wholesale customers shall reimburse the city for their share of those costs as provided in the master water sales contract. The wholesale customers of regional wholesale water suppliers other than the city are responsible for reimbursing the regional wholesale water supplier for their proportionate share of those costs,
through the imposition of water charges.