While this week’s rains forced mandatory evacuations for parts of the city of Lake Elsinore, it’s also brought good news for the lake itself. Canyon Lake dam upstream of Lake Elsinore is overflowing for the first time in two years, sending healthful water to Southern California’s largest natural freshwater lake. The lake periodically experiences dead fish on its shores and closures to people because of high levels of bacteria and algae as well as low oxygen levels in the water.