Water risks are an urgent global challenge. Most public health crises are already driven by water, including floods, droughts and water-borne diseases. Climate change is worsening the problem by intensifying floods and drought, shifting precipitation patterns, altering water supplies and accelerating glacial melt and sea level rise. Clean water supplies are vital for human health, industry, agriculture and energy production, making water risks a major humanitarian threat. Identifying, understanding and responding to these risks requires transparent, publicly available data.