In 1990, Maggie Creek was drying up every summer. The water ran fast and shallow, and by August it turned into a dusty gravel bed. It was too warm for trout. The willows were gone.That same year, a young rancher named John Griggs was hired at a cattle ranch covering roughly 200,000 acres. One of his first jobs was to take a box of dynamite to Maggie Creek and blow up a beaver dam. He knew one thin…