Unless you're partial to polluted water, don't fill your bottle during or just after a major storm. That's the word from researchers at the University of Arkansas (UA), who found that storm runoff creates "dramatically" higher-than-normal levels of pollutants in water sources. And how high is that? "During one storm...phosphorus concentrations in the Illinois River surpassed (levels) estimated for the entire previous year," said Thomas Soerens, a UA civil engineering professor. The findings are based on 2 years of testing.