The pictures — of children with sunken eyes and shriveled skin; oxen being herded across a river where women clean their clothes and fill their pitchers; an African villager sipping water from a shallow puddle — made the point like no words could at the May 11 Center for International Development symposium “The Impact of the Global Water Crisis on Health and Human Development” at the Harvard School of Public Health (HSPH). Still, the statistics were almost equally startling: More than a billion people worldwide lack safe water sources, and 2.6 billion — 40 percent of the world’s population — have no basic sanitation. Nearly 2 million people a year, 90 percent of them children under 5, die from dehydration and associated malnutrition and microbial diseases.