The Boundary is a Slippery Slope: What is a Watershed?

The Boundary is a Slippery Slope: What is a Watershed?

So, what is a watershed? It is defined as an area of land that drains all streams and rainfall to a common outflow point like a main river, reservoir or bay. The water runs downhill in streams and creeks from higher elevation to lower elevation. The term is often used interchangeably with drainage basin or catchment. A watershed includes surface water like lakes, streams, reservoirs, and wetlands, as well as groundwater. Groundwater is the water that percolates into an aquifer instead of running downhill. The size of a watershed can change depending on the scale of observation.  For example, a watershed can be a single lake or can encompass thousands of square miles and can contain lakes, streams, rivers, reservoirs and groundwater. Often a watershed is made up of multiple drainage basins that all drain to the larger watershed. Hills and ridges separate drainage basins from each other.   

Diagram models a watershed, with all the water flowing to a single body of water

 In the high mountains of the Sawtooth’s, there are many ridges and valleys that result in water draining in different directions, thus contributing to many different drainage basins. These basins all drain into the Salmon River, which continues to be one of the most pristine watersheds in Idaho. This watershed is located in Custer, Lemhi, Valley, and Idaho counties. The eastern side of the Sawtooth Mountains is drained by the South Fork of the Payette River.

Warbonnet Peak and ridgeline divides two different drainage basins Photo: Sawtooth Mountain Guides

Hikers often travel to the backs of valleys or follow ridgelines that separate two drainage basins. For example, one drainage basin that flows to the Salmon River watershed is the Iron Creek Drainage which collects all the melt from peaks surrounding the popular hike to Sawtooth Lake and Alpine Lake. 

Snowmelt drains in Sawtooth Lake which flows into Iron Creek drainage basin

Other major drainages that flow into the Salmon River watershed include the Redfish basin, and the Pettit Lake basin which includes the smaller Twin and Alice lakes. All of these waters will join the Salmon river which then flows downstream 425 miles eventually draining into the Snake River.

Map of the upper Salmon River watershed located in the Sawtooth Valley

It is important to be aware of these different drainage basins for a better understanding of the usage of the SNRA. Groups larger than 12 who are planning to hike into the wilderness must be separated by a drainage basin or by a day. Thus big groups must either split into different drainage basins or travel on two different days. Large groups have bigger impacts on wilderness, and it is important to limit our impact as we continue to support its preservation. These impacts include more human waste and trash left behind, littering the forest. Furthermore, a large group might unintentionally disturb surrounding plants by using more tents than the site can accommodate. 

In an effort to preserve our Wilderness, understanding the flow of water and where it leads can lead to a greater understanding and respect for the area. Water continually flows downhill into more bodies of water, so the less impact we can have on water upstream, the healthier the habitats and ecosystems will be downstream. Let’s continue to protect our precious waterways so many more generations can experience them.

CeAnna Schwartz is a 2021 Naturalist at the Redfish Visitor Center. She enjoys hiking, exploring different alpine lakes and observing the change in vegetation as the elevation changes.


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