Not much rain falls in the desert city of Tucson, Arizona. And as the climate warms, it’s getting even drier. So when it does rain, it pays – literally – to make the most of it.

The city of Tucson pays residents up to $2,000 to help cover the cost of a storage tank that collects rainwater. The idea is to get people watering their plants and gardens with harvested rainwater. That helps conserve the municipal water supply.

But some residents are concerned about contamination in harvested rainwater, especially in communities near sources of pollution. So before residents use rainwater in vegetable gardens, they want to know that it’s safe.

Imelda Cortez visits families, bringing materials to test their water.

She works with an initiative called Project Harvest. The program helps residents test the rainwater they collect for E. coli and other contaminants so they know if their water is safe.

Researchers also track the data so they can help communities develop guidelines on using harvested rainwater safely.

It’s a way to empower people with the knowledge they need to keep their families safe and prepare for a water-scarce future.

Reporting credit: Sarah Kennedy/ChavoBart Digital Media.