The water supply for human use and agricultural production is under ever-increasing pressure. Our planet’s population is projected to grow by another 2 billion in the next two generations. Water demand is increasing; water supplies are not. The unforeseen consequences of climate change create additional uncertainties, both locally and globally. Feeding this growing world population is directly correlated with our ability to “green” the water in our agroecosystems by reducing our “blue” and “grey” water footprint. This step will require a coordinated effort by scientists and practitioners from many disciplines, including agronomy, geohydrology, plant physiology, ecology, sociology, economics, and others. Speakers and panelists will address our world’s water supply from three perspectives: blue, green, and gray. Blue water is the available fresh water (surface and ground water) minus runoff and environmental maintenance requirements. Green water is the total amount needed by the crop for its life cycle, including water transpired by plants, used for crop harvest, and stored as soil moisture. Gray water is the water polluted after production of goods and services, broadly termed "wastewater." Agronomic productivity and economic security depends on an adequate green water supply. Scientists face the escalating challenge of greening the world’s water supply by improving how we use water -- blue, green, and gray -- while recognizing the practical, legal, and economic constraints.