We measure water stress with satellites, model it with algorithms, see it in empty riverbeds and experience it with dry taps.

But how do we define water stress? Where does it come from? How will climate change disrupt the supply and demand for water? What is the relationship of water to food and energy?

These questions and more are explored by Charles Iceland, director of Global and National Water Initiatives, in a new podcast. With Aqueduct, he monitors water stress around the world, identifying shrinking reservoirs to watch and dangerous areas for river floods.

Iceland is particularly interested in the intersection of water stress and human security. He recently authored a Commentary, "Water Stress Helps Drive Conflict and Migration," that tackles the intersection of water stress and conflict, and argues that despite development we remain vulnerable to the age-old problem of drought.

As people gain in affluence, they use more water—but world supply isn't growing. We aren't helpless: we can identify water-efficient crops, expand water storage infrastructure, raise water prices, and, most of all, transform the food system. "Solving the problem of agriculture is the first thing you need to do in solving the water puzzle," Charles says.

There may be tradeoffs, but the water challenge is not insurmountable.