The Bay Area imports most of its water and relies on the Sacramento-San Joaquin River Delta and its tributaries for about 70 percent of its supply. Those supplies face an uncertain future as a changing climate shrinks the Sierra snowpack and raises sea levels, and a declining ecosystem results in further restrictions — all while the Bay Area’s population and economy continue to grow. The stark reality is that 25 million people and 3 million acres of farmland are at risk of losing up to 20 percent of their future water supplies if the status quo continues in the delta.