Stress. When stream flow peaks earlier in the spring owing to warmer temperatures, low stream flow begins earlier in the summer and lasts longer in the fall. These changes stress aquatic plants and animals that have adapted to specific low-flow conditions. The survival rates of fish such as salmon and trout are known to diminish when water levels in rivers and streams are dangerously low, for example. That's partly because bears can snag spawning salmon more easily in very shallow water, as the salmon struggle upstream.