Salmon River

Basin Overview:

The Salmon River is located in Idaho and it is about 425 miles long. Its basin drains around 14,000 square miles of watershed with its main tributaries being the  Yankee Fork ,  Panther Creek ,  Middle Fork Salmon River ,  South Fork Salmon River ,  Little Salmon River ,  East Fork Salmon River ,  Pahsimeroi River ,  Lemhi River , and the  North Fork Salmon River . Additionally the Middle Fork of the Salmon River acts as a tributary watershed. Its bed is composed of dense quartzites and limestone deposits. The Salmon River drops more than 7,000 feet between its start near Galena Summit and its end in the Sawtooth Valley. The upper Salmon River Basin has a drainage area of around 4 million acres, and the river in total drains around 11,060 cubic feet per second of water into the Snake River. The Salmon River provides the time zone boundary for Idaho, with northern Idaho being on Pacific time and the rest of Idaho being on Mountain time. This river is also one of the largest rivers in the continental U.S. without a dam on its mainstream. The area around the Salmon River has a relatively diverse climate with peak rainfall happening in the early summer (around 1.5 inches). The Salmon river receives, annually, around 9.54 inches of rainfall and around 25 inches of snowfall. Its average high is 85 degrees fahrenheit in July, and its average low is around 11 degrees farenheit in January. Typically it is also very dry around the Salmon River. The exact location of the Salmon River would be at  43°47′48″N 114°46′36″W , which translates to it being near Norton Peak in Blaine County. It is located in the Pacific Northwest of the United States in the middle of Idaho.

River Regime Chart:

The discharge at the USGS Station in White Bird Idaho increases about six times its usual flow in the months April, May, June, July, and the first few weeks of August. This is because the main input into the Salmon is snowmelt. After the winter months, the snow begins to melt in March. The discharge increases drastically in these 5 or so months, and then returns back to its normal discharge rate.

System Components:

The Salmon river has year round precipitation that combined creates its total input. The main types of precipitation that the Salmon river Drainage Basin receives is Rain, Snow, and occasionally hail or sleet. In the Spring and Fall it rains on average 0.8 -0.9 inches per month, while in the summer it drops down to about 0.4. Then in the winter the snow averages anywhere from 1.2-1.5 equivalent inches of water per month. This averages out to about 12.3 inches of precipitation per year. There of course are variations to this year by year but the general trend remains the same. 

All of this precipitation is absorbed into multiple different kinds of stores and outputs. The main stores in the Salmon River drainage basin are vegetation, soil, and aquifers. Because of the challenging landscape, urbanization and most human development is very limited. This means there is still a large surface area of permeable soil and vegetation. The vegetation absorbs a large percent of the precipitation, mostly through interception and stem-flow, but the through-fall that is not collected infiltrates into the soil and is from there either percolates into the groundwater, interflows to channel storage, or is absorbed by the roots of vegetation. Another store that is seen in a couple areas of the Salmon River Drainage Basin is aquifers. Although most of the river is not above aquifers there are still a couple sections that are. 

Eventually the water leaves the stores and makes its way to the outputs of the drainage basin. Because the terrain does not support agriculture there are very few farms that source their water from the Salmon River. However, there are orchards and gardens from some of the first settlers. The land along the Salmon River is good for grazing, because cattle do not need perfectly flat and smooth areas. So in the early 1860’s cattle grazing was introduced along the Salmon river. This lasts well into the 1940’s, but sections of land were often overused and still scarred. Today there is permitted grazing allowed only in specific areas. 

Flooding:

Because the Salmon River and its drainage basin is not very developed it rarely experiences large floods. Of course there is the small overflowing of the banks just from large water level years, but there has only been two serious floods on the Salmon River. The first was in 1984 and it’s often called the Ice Jam Floods. In the winter of 1983-84, in the town of Salmon, Idaho the temperatures were consistently below 0 Fahrenheit. This lead to the creation of about 5 ice jams over the course of the winter months. These ice jams would block the flow of river and forced the water over the banks and into the town of Salmon.

The second notable Salmon river flood was the Panhandle Floods in 1996. Similar to the Ice Jam Floods freezing temperatures lead to the formation of ice, and then in February when the weather warmed slightly; it rained for days straight. This brought the river from its flood stage height of 43 feet to 52 feet; 9 feet higher. NOAA considers any flood stage higher than 50 a “major flood stage”. This caused flooding in parts of Moscow, Coordalane (specifically the “panhandle” of the town) , and other susceptible areas. On February 10th, President Clinton declared 10 counties a Federal Disaster Area. The total cost of the flood damage was around $28,030,398. The University of Idaho alone sustained $1.6 million in damage. 

Because there is so much permeable surfaces and vegetation, flooding from surface runoff isn’t a very big problem. However, there aren’t many flood mitigation strategies when it comes to preventing large quantities of water from freezing, but with weather forecasting we can watch out for weather patterns such as rain and then sub zero temps that would lead to ice jams, which then leads to floods. Because of the advanced technology we have, forecasting floods is not a very large problem. The Salmon river is not at risk for flooding 9 months out of the year, but even in the winter these floods can be prevented if they predicted in time. There are not many models for these unpredictable ice jam floods, because knowing were the ice is going to begin to form, and what will follow after is very situation based. 

Unlike other rivers there are not many human impacts on the Salmon River. As the Salmon River flows through the Frank Church-River of No Return, a protected wilderness area, a lot of the Salmon River cannot be accessed by land. As a result, the Salmon River is not used for agricultural purposes such as irrigation. Additionally there are no dams along the Salmon River, and because of this the river is able to contain “70% of the remaining spawning habitat for steelhead and salmon in the Columbia River basin.” (Oppenheimer, 2016).

 As of right now there are no industrial uses of the Salmon River, but there are many proposed projects. One proposed project comes from a Canadian mining company hoping to reopen and expand an open-pit mine that was closed a long time ago. This mining project would unearth arsenic, mercury, and antimony that would deposit directly or indirectly into the South Fork of the Salmon River through natural processes and potential accidents and spills. This would set back the $13 million spent in past decades on restoring the river. Since the restoration of the river levels of heavy metals such as arsenic, mercury, cyanide and antimony have been on the decline. Though there are no industrial uses of the Salmon River yet, there are plenty of recreational ones. The Salmon River plays host to those looking to fish, white water raft, kayak, camp, and so much more. The only detrimental uses of the Salmon River as of right now are overfishing and the use of jet boats. However, the issue presented by jet boats is decreasing as low water levels make sections of the river very dangerous to navigate. Since there are very little human impacts on the Salmon River, this has led to it being one of the most endangered rivers in America. Meaning that the river is host to endangered and threatened species such as Chinook Salmon and Bull Trout, and that the river is one of the clearest free flowing rivers.

In addition to the recreational uses of the Salmon River, it also provides an abundance of things to research. Currently the Idaho Department of Environmental Quality is studying the erosion of the Salmon River bank and the water quality of the Salmon River Basin. The United States Geological Survey is studying the discharge of the river. There is also a study being done my biologists from Biomark in collaboration with the Idaho Department of Fish and Game on baby Chinook. The baby Chinook are fitted with tiny radio tags that allow the scientists to track them. This data will allow for more effective restoration and conservation efforts by the Department of Fish and Game. Since there aren’t any industrial use of the Salmon River there isn’t a Drainage Basin Management Plan. A Drainage Basin Management Plan would help to maximize the economic and social benefits derived from water resources.