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| Winter - Spring 2009 |
Vol. XVIII, No. 1
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Trinity River Flow Releases -
Frequently Asked Questions
- Q: WHAT CONTROLS THE WATER LEVEL IN TRINITY LAKE?
- A: The level of the Trinity Lake works just like your checking account, it is controlled by how much water comes in and how much water is released. The inflow to Trinity Lake is based on how much rain and snow nature provides. Releases from Trinity Lake either go down the Trinity River or are diverted into the Sacramento River through the big pipes you can see coming down the mountain into upper Whiskeytown Lake. The Bureau of Reclamation controls how much water is released from Trinity Lake. This is a difficult task because they have to balance the competing needs for the water (on both the Trinity River and Sacramento River) while trying to maintain adequate lake levels. Releases from Trinity Lake are also cold and are used to meet regulatory criteria for water temperature on both the Trinity and Sacramento Rivers. These water temperature criteria benefit fish and are one of the main drivers of how much water is released in dry years. Current and forecast lake levels can be found on the Trinity River Restoration Program website.
- Q: WHAT IS THE WATER IN TRINITY LAKE USED FOR?
- A: Water in the lake provides excellent recreational opportunities for boating and fishing. Water released down the Trinity River supports the fish and wildlife populations, provides recreational opportunities for rafting and fishing, and also supplies water to local communities in Trinity and Humboldt Counties. Diversions to the Central Valley are made for a variety of purposes including municipal water supply, irrigation, and hydropower.
- Q: WILL FLOWS TO THE TRINITY RIVER BE REDUCED THIS YEAR DUE TO THE LOW LAKE LEVELS?
- A: The answer is both yes and no. The amount of water released down the Trinity River is tied to the climate (i.e. how much rain and snow we get) and ranges from 815,000 acre-feet in “extremely wet” years to 369,000 acre-feet in “critically dry” years. So, yes the river flows are reduced in dry years. However, these legally mandated amounts are fixed, regardless of the lake level.
- Q: WHY IS TRINITY LAKE LOW BUT WHISKEYTOWN LAKE IS HIGH?
- A: The main purpose of Trinity Lake is for water storage. Lake levels have dropped over the last several years in response to a high demand for water. Whiskeytown Lake acts as a pass through for the water diverted from Trinity Lake into the Sacramento River. Whiskeytown lake is kept full in order to keep the water going to the Sacramento River as cold as possible. Whiskeytown lake is drawn down by approximately 10 feet in the winter as a flood protection measure. Keeping the lake full provides excellent year round recreational opportunities and forms the heart of the Whiskeytown National Recreation Area.
- Q: WHAT ARE THE SCHEDULED FLOW RELEASES FROM LEWISTON DAM INTO THE TRINITY RIVER?
- A: Flows are kept at 300 cubic feet per second (cfs) through the winter months and then come up at the end of April. The actual flow schedule for the rest of the year is set in mid-April, after the water year is classified and we know how much water is available for release. The final release schedule is then posted at the Trinity River Restoration Program website. The website also has information on current and forecast river conditions and lake levels, and lets you sign up for automated announcements of flow releases changes via email or phone. Feel free to call the Trinity River Restoration Program (530-623-1800), or better yet, stop by the office at 1313 S. Main St. in Weaverville (next to TOPS supermarket) if you can’t find the information you want on the website.
- Q: HOW DOES THE BUREAU OF RECLAMATION DECIDE TO MAKE HIGHER FLOW RELEASES TO THE TRINITY RIVER DURING THE WINTER?
- A: During the winter, the Bureau of Reclamation maintains lower levels in Trinity Reservoir to provide a buffer in the event of an extremely large winter storm. The quantity of that buffer is based on several factors, and primarily references many years of hydrologic record for the basin. Maintaining storage space is a very important aspect of flood control operations, and is fundamental in protecting areas downstream of Trinity Dam, as well as the dam itself. As winter storms fill Trinity Reservoir, the Bureau of Reclamation may need to increase releases to the Trinity River to maintain the lower lake levels. Because these elevated winter releases help protect the dam, they are commonly called "Safety of Dams releases" and may or may not occur in conjunction with actual winter storms. Safety of Dams releases are typically no greater than 6,000 cfs, but may go higher if conditions warrant.
- Q: WINTER STORMS CAUSED TREES AND OTHER WOODY DEBRIS TO FALL INTO THE RIVER NEAR MY HOUSE. DOES THE TRINITY RIVER RESTORATION PROGRAM PLAN TO REMOVE THE DEBRIS FROM THE RIVER?
- A: The Trinity River Restoration Program has no authority, and is not responsible, for removing woody debris from the river. Private landowners and public land management agencies make decisions about removing debris that might impair public safety, threaten the integrity of bridges or other structures, or increase the likelihood of local flooding. If landowners elect to remove debris, we urge that landowners are cautious and follow safe work practices. If left within the watercourse, fallen trees and bushes do play an important role in the juvenile life stages of fish in the river. Large woody debris provides cover, shade, and structure for fish. It also causes local scour that refreshes gravel, and increases the number and size of pools or holes for fish to utilize during low flow periods. Large woody debris contributes to the geomorphic processes, resulting in the creation and maintenance of the complex river habitats required by Chinook and Coho salmon and steelhead.
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