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Streams and Watersheds - Importance of a Watershed Perspective

Figure 1-2
The sinuous pattern of this valley bottom illustrates how stream channels shift over time.

Even though the watershed may cover a large area, what happens in one part of the watershed may have both direct and indirect effects on other portions. For example, installation of an irrigation diversion in the upper portion of the watershed may result in a reduction in the amount of water which moves through the channel further downstream. This could change the type of vegetation that can grow in riparian areas in lower portions of the watershed.

Another example: a timber harvest in the upper part of the watershed may result in more water flowing into the channel over a shorter period of time because less is being used by large, deep-rooted woody vegetation. The result could be higher overbank flooding in some years or increased lateral or vertical cutting because the increased volume of flow places additional pressure on streambanks and the channel bottom.

On the other hand, what happens along the stream can affect the uplands. Suppose you wished to improve the vegetation on streambanks in a riparian area. One way to do this would be to manage livestock use of the riparian portions of the pasture. Pushing stock out of the riparian area means they will spend more time in the uplands.

One important result will be better use of all forage resources in that pasture. At the same time, this increased use of upland forage may affect other management considerations. For example, if these upland areas are providing winter range for elk and maintaining this herd is one of your objectives, your stocking rate considerations should also include elk use levels.

Riparian areas are the link between the uplands and the stream. Different types of streams affect riparian areas differently, just as the presence of different riparian vegetation influences the nature of its related stream.

Understanding the different types of streams you may encounter and being able to recognize how they interact with their riparian areas will enable you to make more effective management decisions.