The snowpack in the Sierra Nevada is the deepest it’s been in decades, but those storms that were a boon for Northern California won’t make much of a dent in the long-term water shortage for the Colorado River Basin — an essential source of supplies for Southern California. In fact, the recent storms haven’t changed a view shared by many Southern California water managers: Don’t expect lakes Mead and Powell, the nation’s largest reservoirs, to fill up again anytime soon...