Upper Trinity River Watershed Monitoring Plan
The Upper Trinity River Watershed mostly has been ignored in terms of analyzing sediment sources that would impact beneficial uses of these waters, including water supply, recreation and salmon habitat downstream of the dams. However, at least three big storms in the past 30 years (Dec 1964, Jan 1974, and Jan 1997) have resulted in high levels of turbid (muddy) water being released into, and from, Trinity Lake with potentially significant impacts on fish, recreation and water supplies. This part of the Trinity River can no longer be dismissed. It seems likely that watershed restoration activities also need to be implemented in the upper watershed where opportunities present themselves.
A monitoring plan for looking at the Upper Trinity River watershed recently has been developed. It cannot tell us everything about the streams that flow into Trinity Lake, but it can give us some idea of what happens when we get heavy rains or those more spectacular “rain on snow” events like 1997. Collecting information from some of the streams will give us a snapshot of the amount of water, and the amount and types of sediment that travel down these streams into Trinity Lake. This information will help provide a baseline to evaluate long-term trends throughout the watershed. The District has worked closely with land mangers, especially the USFS and BLM, in other parts of the Trinity River watershed, like Grass Valley Creek and the South Fork of the Trinity River, to take these kinds of “snapshots” and use them to design and implement projects that reduce the movement of soils (erosion) into streams during heavy rains.
Some of the types of information that will be gathered over the next year will be stream flow; the amount of water in streams related to the amount of rainfall during a storm, sediment loads; the amount of finer soils that get carried downstream during those same storms, changes in the shapes of stream channels and the deltas that form at the mouths of streams, and reviewing recent aerial photographs to map landslides.
This type of monitoring only provides a piece of the picture, though. The first-hand knowledge of people living and working in the watershed is very important, too. That is why the District sent out a landowner survey in January. We want to tap your observations and mine your understanding of the streams and forests that you live with, whether it is all year long or just for a week or two in the summer. Later this year, we’ll also invite folks to sit down and share their thoughts. So keep an eye out for details on these up-coming workshops.
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