Three months pregnant and queasy with morning sickness, Yasmin Acosta Ruiz pushed a cart laden with buckets of water through the scorching July heat. As she and her 7-year-old son eased the cart over a speed bump, water sloshed onto the pavement. They both winced.

Here on the outskirts of Monterrey, a sprawling industrial city that has become the face of Mexico's water crisis, every drop counts.

Drought has drained the three reservoirs that provide about 60% of the water for the region's 5 million residents. Most homes now receive water for only a few hours each morning. And on the city's periphery, many taps have run completely dry.