“Lots of them die of thirst while crossing,” said Enrique Morones, his arms full of water bottles near the fence in California’s Imperial Valley designed to stem the tide of migrants from central America.

“The lack of water is the primary cause of death for the 10,000 people who have died while illegally crossing these desert regions,” said Morones, a Mexican-American from San Diego who founded Border Angels 20 years ago.

Staff members leave the large water bottles under shrubs on both sides of the border, from Sonora and Baja California in Mexico to Arizona and California.