A very interesting article from the California Water Blog about the intersection of the three and water temperature, so crucial to optimal salmon health.
Summer has just begun and conditions on many of California’s drought-stricken rivers and streams are already looking grim for cold-water fish.
Endangered winter-run salmon may not survive a repeat of last summer’s nearly total loss of eggs and fry from an over-heated Sacramento River. Low and warm flows in the Russian River watershed are threatening coho salmon and steelhead, prompting emergency water restrictions. And, last week, the state began evacuating rainbow and brown trout at the American River and Nimbus hatcheries to prevent die-offs over the summer.
However, not every California stream will turn perilous. In fact, some spring-fed streams are likely to become more hospitable during the dog days of summer.
Our on-going investigation of Big Springs Creek near Mount Shasta found that from May to August – when California streams generally warm up – maximum water temperatures cool by almost 3 degrees Fahrenheit. The cooling is all the more remarkable considering the creek is practically devoid of shade trees.
How could this be? The answer lies just below (and above) the water surface: aquatic plants.
Generally, the best way to maintain cold-water fish habitat is to keep cold water cool – because once water warms, it’s difficult to reverse the trend. In Big Springs Creek, plants known as macrophytes help to provide that benefit in the absence of shade trees. Just as streamside trees form a shady canopy over a creek, mature stands of these rooted vascular plants create a sun-blocking umbrella within the creek channel.
The plants typically grow in spring-fed streams with stable flows, open canopy and low gradient. Big Springs Creek nourishes an abundance of macrophytes because its waters are enriched with nitrogen and phosphorous from volcanic and sedimentary rock.
Retrieved July 1, 2015 from http://californiawaterblog.com/2015/06/30/creeks-that-cool-down-as-summer-heats-up/