Seven years ago, a pulse of water on the Colorado River at the U.S.-Mexico border temporarily reconnected it to the Pacific Ocean. Scientists used the so-called “pulse flow” to study what plant and animal life returned to the desiccated delta along with water.

The massive reservoir on the Colorado River hit a new historic low on July 24, dropping below 3,555.1 feet in elevation. The previous low was set in 2005. The last time the reservoir was this low was in 1969, when it first filled.