By David Wartinbee, for the Redoubt Reporter
The weather is a common topic of casual conversation, and many of us have commented that this summer has already been warmer than anything we saw last year. Not only have we been experiencing warmer temperatures, but we have also received a lot less rain than last summer.
Even though many of us are forced to water our gardens frequently because the soil is so dry, that doesn’t mean the Kenai River is drying out, too. Even with the lack of rainfall, the river level is still fairly high, about where we usually see it in July.
The reason the Kenai River is able to maintain its discharge levels is probably due to the fact that the Kenai has about as many different sources of water as any river can have.
A primary water source for just about all rivers is surface runoff. This water arrives as rain or snow and constitutes water the ground cannot absorb. If there is a large rainfall and soils can no longer absorb more water, we get sudden bursts of runoff and possible flash flooding. In desert rivers with very little runoff, we tend to see dry creek beds and rarely do we actually see water flowing.
However, desert dwellers often dig down into the dry streambed until they find groundwater or springs. Springs are simply places where underground aquifers flow to the surface from porous rock or gravel layers. Groundwater from adjoining aquifers is a major source for many streams and rivers. When the Kenai River is frozen over and snow is piling up, it is the groundwater that keeps the river flowing under the ice. During summer months when higher stream levels occur, our streams can recharge the underground aquifers.
The underground water source is an almost constant supply, and we put that to our own use when we drill water wells. Wells reach deep enough to enter an underground aquifer that has water flowing all year long. We simply pump out water from a deep cavity in the aquifer when we need it.
There are a number of lakes within the Kenai River watershed that supply an important portion of the river discharge. We often say that Kenai Lake is the start of the Kenai River, but there are many other lakes that release water destined for the river, including Trail Lake, Upper Russian Lake, Juneau Lake, Cooper Lake and Mackey Lake. If you get out a topographical map and look carefully, you’ll need both your hands and toes to count all of them.
Another water source for the Kenai River comes from melting glaciers. The expansive Harding Ice Field in the Kenai Mountains forms a variety of glaciers, such as the Snow Glacier and Skilak Glacier. These glaciers and ice fields release water primarily during summer months, when the air temperatures rise.
However, water can become dammed up near the terminus of the glacier. Sometimes, glacier-lake releases can come in spurts and have a big impact on overall discharge. Skilak Glacier’s terminus lake released a couple winters ago and caused a very destructive ice jam to move downstream along the Kenai River.
The Snow Glacier often dams water behind an ice mass, and periodically it can release large amounts of water that feed into the Kenai River. Additionally, these glacial meltwater sources often carry fine, suspended material into the water, called glacial flour, and can give it a distinctive, milky or pearlescent coloration.
The last water source for the Kenai River is melting snow. It might be easy to assume that snowmelt is only important in the spring, since that’s when we see the snow disappear from our driveways and lawns. But snowmelt is a major contributor to our feeder lakes and the Kenai River throughout spring and summer.
As air masses warm during the summer, they rise up the mountain slopes and melt higher and higher snow deposits. We sometimes notice the snow levels rising up the mountains as the summer progresses. Obviously, snowmelt continues until the temperatures drop once again in the fall.
Each of these water sources will play a role in determining the river discharge. The exact portion or importance of each of these water sources will vary throughout the seasons. As we currently experience warm, dry conditions, surface runoff is less important while snowmelt, glacial melt, lake outflow and groundwater become more important.
In the winter months, surface runoff, glacier melt and snowmelt will diminish to next to nothing, and groundwater and lake discharge will be the major sources. Perhaps you have noticed that the Kenai River is fairly clear in the winter but becomes distinctively cloudy in the summer. It all depends on where the water comes from.
David Wartinbee, Ph.D, J.D., is a biology professor at Kenai Peninsula College’s Kenai River Campus. He is writing a series of columns on the ecology of the Kenai River and Cook Inlet watershed.