Trash is piled near the U.S.-Mexico border, where sewage from Tijuana flows through. / Photo by Adriana Heldiz On a stormy day, 1 billion gallons of water can rage down the river crossing from Tijuana to San Diego. None of that water is captured for reuse now among the two desert cities it splits, which are regularly prone to drought, because it’s considered polluted by sewage spills on the Mexican side. If successfully recycled, that water could prove to be valuable as the Southwest grows more water-uncertain due to climate change. Even so, the occasionally raging river is starting to turn heads in the private sector from companies that’d like to own the water, treat it and sell it back to a government or other thirsty buyers. To get there, it might take securing rights to the water from the state of California or, possibly, a new international agreement.