The dark hump of a bottlenose dolphin’s back cuts through the surface of the Corpus Christi Ship Channel, appearing briefly alongside a docked, Hong Kong–registered bulk-cargo vessel. This industrial canal is an unlikely haven for wildlife, but dolphins are attracted by its cool waters and abundant mullet and appear so regularly that local captains take tour boats to see them.From the observation tower under the downtown Harbor Bridge, a pedestrian can also spy the bend in the channel, a mile and a half away, where the city is placing pipes to feed its planned Inner Harbor desalination plant. Water will be sucked into the facility and stripped of its salt and other minerals by reverse osmosis. The clean water will be routed into the city’s…