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Discussion Starter #1 (Edited)
Below is a hydrograph of the proposed March 2021 release schedule out of Glen Canyon Dam.

A friend launching in March contacted me concerning rapids at 4k flows, specifically Horn, Crystal and Bedrock.

Do words of wisdom exist for these and other rapids at 4k flows?

How about other words of wisdom such as watch your step on muddy landings?

61956
 

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Likewise, I’m interested in what happens at 25k; I’ll be launching right at the beginning of the flood.
 

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The Bureau of Reclamation is proposing maintenance and repair for one week in mid-March at the bottom of Glen Canyon Dam, approximately 15 miles above Lees Ferry. If this happens water flow coming out of the dam into Grand Canyon would be reduced to 4,000 cfs from March 15-20. Then, to make for the scheduled monthly water release from the dam in March, the flow would be increased over the next three days to near 25,000 cfs from March 23-26. After that it will drop again, back to the normal monthly flow range of 10-15,000 cfs.

GCPBA has been in contact with a representative of Glen Canyon dam. Discussions regarding the work schedule are underway. The increase to the 25,000 cfs power plant capacity following the maintenance repair would need approval from the Secretary of Interior, or acting Secretary, prior to its implementation after the scheduled maintenance and repair work. The final authorizations are being prepared, but no official signatures have approved the increased flow plan. Final decisions are anticipated mid-February.

These flows will be quite exciting and important for Grand Canyon boaters. A lot of attention will need to be paid to boats tied up overnight at beaches during the drop from 10-15,000 cfs to 4,000 and then the subsequent rise to 25,000. During the drop boats can quickly be left very high & dry in just a couple of hours, and with the rise boats can come loose from sand stakes and float away. Camping gear left low on the beach can also be washed away or become deeply submerged.

Many rapids will change dramatically at low & high flow. Among the rapids more difficult and/or rocky at 4,000 cfs will particularly be House Rock, the Roaring 20's, Hance, Horn Creek, Crystal, Bedrock, and Deubendorff. Many rapids will have much bigger wave trains and other features at 25,000 cfs.

It will be interesting to see how much, if any, beach building comes from the increase to 25,000 cfs flow. When there was a 40,000 cfs high flow experiment in past years some beaches were very nicely expanded from the stirred up sediment on the river bottom. In some cases the larger beaches lasted for six months or so.

GCPBA will update you on this situation when we receive additional information.

This was first reported in the Boatman's Quarterly Review, vol. 33, #4.

GCPBA RiverNews is a service of Grand Canyon Private Boaters Association.

Join and Support GCPBA. Visit our website www.gcpba.org.
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I ran Horn in the mid 80's at around 4000 or so when they were working in the dam. The only run I could see was down the far right side punching a series of big holes. It was very steep and the momentum carried me through. I just missed the rock shelf on the right by a couple of feet. Some of the other small drops had sneaker holes like 83 mile. Badger was pretty rocky and hard to see a line. I don't remember anything else being that hard, Crystal was just a class three boulder garden. We had some long days due to the low water.
25,000 back them was a pretty routine daily high flow and a lot of the drops start to wash out especially the 20's. Left run at Lava is open and pretty easy. Been a while but can't remember any other rapids being that tough at 25,000. In my opinion the best (toughest)? level is around 17 to 18 thousand.
 

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I ran down there in the 90's, the lowest I saw was just under 6k. At that level, Horn was a right to left move, ducking behind the right horn. It is really fast. The way the move was described to me was when you think it's time to start pulling you should have been pulling when you had that thought - meaning a fraction of a second can make a big difference. Crystal was straight forward, but the penalty of the rock garden was magnified. Things have shifted/filled in at Bedrock since then so I don't think anyone really knows how narrow the right slot will be.

25k is the sweet spot for most rapids in my opinion.
 
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