A reservoir capable of holding 1.6 billion gallons of recycled water is set to sustain south Orange County by the end of 2019. Once completed, the Trampas Canyon Reservoir will store enough excess treated water in the winter months to meet irrigation demands in the region during the summer. It will also be the largest surface water reservoir in south Orange County, with the capacity to hold more than one-half of the recycled water the district will generate from its nearby Chiquita Water Reclamation Plant, officials said.