Trouble with Temperature
Elevated water temperature in local waterways is due primarily to lack of adequate streamside shading. Depending on the waterway, elevated temperatures can be hazardous or fatal for cold water fish such as salmon and trout. Water above established parameters can hamper the survival of juvenile salmon, prevent natural fish migration and much more.
Tree lined riparian corridors are a thing of the past in most communities. Development has not been prevented along waterways and many cities do not have tree protection ordinances in place. Trees shade water which blocks incoming solar radiation. The larger the surface area of the waterbody, the more heat can be absorbed by the water. It’s important to note that shade does not cool the water, but foliage blocks the incoming radiation. Elevated water temperature can impact the health of cold water fish such as salmon and trout.
In large bodies of water such as the Willamette River, streamside shading does little to help cool the water. In these cases we look toward shading in the smaller streams in the watershed. The health of clean, cool streams that discharge to the main stem of the stream play a crucial role in keeping the larger waterbody healthy.
Temperature is not a stormwater pollutant as it isn’t washed directly or indirectly into receiving waters. However, urbanization has resulted in cities that have acres of impervious surface that does absorb solar heat. It is reasonable to assume that direct runoff is warmer as is the stormwater from point sources. Large areas of impervious surface are sometimes referred to as urban heat islands.
What can I do to help reduce temperature in local streams?
Did you ever notice that the vegetation along waterways often includes tall trees, smaller shrubs, and sometimes grasses or vines? These plants all play an important role in providing a healthy habitat for wildlife and everything that lives there – even us.
Tall trees are especially important to stream health for a number of reasons such as bank stabilization, large woody debris for fish, and more. But trees also play a major role in blocking incoming solar radiation from warming the water in our waterways. Trout and Salmon are more sensitive to warm water than some other fish. While some adult fish may be more able to withstand increasing water temperature, for spawning and hatching of eggs, much lower temperatures are required. Many species spawn only above or below certain temperatures.
What can you do to help?
- Contact your local watershed council and volunteer for a restoration project;
- Plant a tree and care for it properly. Whether near a stream or far away, trees do a remarkable job of removing pollutants from the air and soil. They also cool the environment in general;
- Explore the use of native plants in your yard or in a neighbors yard;
- Support green infrastructure projects in your community such as rain gardens or vegetated swales.
- Build your own rain garden;
- Educate yourself and spread the word. Green is good!
Polk County native plant resource: Native Plants - POLK SOIL AND WATER CONSERVATION DISTRICT (polkswcd.com)
