Despite all that work, only about 9 percent of the total original intake ­becomes potable water (or goes to generate electricity). The rest—now with a higher salinity—gets pumped back into the Persian Gulf. In 2015, that translated to more than 1.3 trillion gallons of discharged brine. DEWA keeps a close watch to ensure all that warm salt water doesn’t harm the local ecosystem. At multiple distances from the plant, workers routinely test the sea for things like acidity levels and the health of marine life.

Spencer Lowell