As the Stillwaters Stream Monitors ventured out on a raining Sunday ready to take measurements of dissolved oxygen, nutrients, water and air temperature, bacteria, flow velocity and other physical measurements, they were only scratching the surface of measuring waterway health. Just like the human body, we take measurements to try to understand our condition but there are so many unknowns. Our streams, rivers, and estuaries are just the same.
When ecologists try to understand the health of a waterway they look at three basic qualities or building blocks — process, structure, and function. Let’s explore these three qualities.
First there are processes. Many chemical processes go on simultaneously in a stream every minute. Oxygen is a good example. The amount of oxygen that will dissolve in Carpenter Creek is dependent on the temperature. Low temperatures will allow more oxygen to be dissolved. That’s good for stream critters. There are also biological processes that affect the oxygen. If you have lots of aquatic plants in the water, big (seaweed or grasses) or small (phytoplankton), you have little oxygen generators. However, as those plants die, bacteria breaks down their molecules and uses up oxygen in the process.
Other kinds of processes like photolysis, chemical reactions caused by exposure to light, transform chemicals in the water. Sediments on the bottom also release sulfur (that rotten egg smell) and nutrients into the water column. To differing degrees, all these processes are happening all the time, some mediating others.
The second quality of a waterway is its structure. Any stream or river we walk near exhibits many different aspects of structure. It will have a variety of shallow and deep areas. It will have wider and narrower areas, and may meander. Each physical feature determines how fast the water can move through that portion. It will also determine the grain size of particles that settle on the bottom. Faster-moving water means larger particles. Slower-moving water leads to silt and mud buildup. What substrate you have on the bottom will determine what lives on the bottom, and thus food that is provided for fish or birds.
We humans are pretty good at changing the structure of our waterways. Just look at Lake Washington and the Ship Canal in Seattle. The ship canal was created on paper by the Corps of Engineers and built. It did not exist naturally. Many of our waterways have been straightened, deepened, or “tidied up” by removing big logs or other debris. Unfortunately that debris structure has many important jobs. It physically scours out deep pools for fish to rest and hide in, and provides habitat for insects to nest on, and more.
Finally, function is another important quality. As mentioned earlier, streams can only support spawning fish if they have the right gravels where fish eggs can be protected by still receive oxygen. Streams can only successfully support insects (fish food) if they have the rocks for them to live on or under and with enough bacterial and plant growth for the insects themselves to fed. Streams can control flood waters as their shape allows water to rise and spill into adjacent floodplains, if not impeded by alteration by man. We have certainly been aware of this important stormwater management function recently.
Just like our bodies, we will never fully understand how they work or stay healthy equilibrium. They are marvelous, miraculous systems, and they need our help to survive.
Betsy Cooper is a volunteer Stream Monitor for Stillwaters Environmental Education Center.
