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Difficulty V
Length Miles
Gauge N/A
Flow Range
Reach Info Last Updated 10/31/2013 7:35 pm

River Description

This spectacular granite canyon has many class 4 and 5 rapids with some class 5+ rapids at around 800 cfs.   In addition there are 8 rapids that flow into boulder sieves and must be portaged.   At lower flows, such as 350 cfs, even more rapids may need to be portaged.

First Descent account:
On June 11th, 2002, a team of boaters assembled below the stunning 450-foot spillway of Donnells Dam on the Middle Fork of the Stanislaus River in California. This stellar group was invited to help American Whitewater chart the boating opportunities on the Middle Stanislaus for the relicensing of 6 dams and powerhouses on the Middle and South Forks of the Stanislaus River. The stairway of hydropower dams and diversions divert water around this eight-mile reach of the Middle Stanislaus as well as five other whitewater reaches.

As a result of the dewatering, this reach of the Middle Stanislaus, known as Hell's Half Acre, had eluded many elite boaters looking for a first descent. The river averages a gradient of 183 feet over the eight-mile length with individual miles ranging from 220 to 150 feet per mile. The team of boaters included Dustin Knapp, Alex Nicks, Jared Noceti, Scott Collins, Lars Holbeck and John Gangemi.

The utility, TriDam, and numerous stakeholders in the hydropower relicensing proceeding felt American Whitewater's interest in this reach was foolhardy. Afterall, the chosen name for this reach, Hell's Half Acre, they felt was symbolic of the terrain. In their opinion this reach would certainly not be navigable. American Whitewater persisted in the relicense process advocating for a feasibility study to determine the following: 1) the navigability of the reach; 2) the whitewater difficulty; 3) if possible, identify appropriate flows for whitewater recreation; and 4) determine if further study (i.e., controlled flow study) was warranted. Furthermore, the new license would be granted for 30 to 50 years. Who knows what boaters will be paddling in the year 2025? The study was scheduled for June 10-11, 2002.

To meet TriDam's liability concerns several of the boaters flew the reach by helicopter equipped with a video camera on June 10th. Back at TriDam's offices in Strawberry, the entire team of boaters viewed the video footage and poured over topographic maps and aerial photographs of the reach. The team of boaters collectively gave the green light to proceed with the feasibility study the next day. The stage was set for the adventure into unknown rapids of the Middle Fork Stanislaus below Donnells Dam.

So what mysteries did the team unravel? They found a classic sierra run on polished granite with continuous Class IV-V paddling opportunities. The rapids were almost overshadowed by the stunning granite walls and boulders throughout the run. My eyes kept tracing the countless unclimbed crack lines leading out of the water. A total of eight rapids were portaged due to boulder sieves. Several other Class V+ drops were portaged selectively by some team members. Don�t let the portages discourage you-- all of the them were relatively short on spectacular granite bedrock and boulders with several terminating in fun seal launches.

Next Steps: American Whitewater will now apply the results of this feasibility study in the negotiations with TriDam for a new hydropower license. Hell's Half Acre is not only navigable, it's a whitewater gem. The lack of reliable and timely flow information for the public is clearly a deterrent to whitewater use. American Whitewater will work to get real-time flow information for this reach, access improvements and evaluate the need for scheduled whitewater releases. The outcome of these negotiations will be posted on the American Whitewater website and in the journal.

Why Go? The put-in alone will blow your mind. Water spills 450 feet from a granite apron to the river below. If this isn't enough check out the continuous rapids and backdrop of this stellar gorge. There is dispersed camping at the take-out or along the road to the put-in.

Directions: From Sonora, California take highway 108 to the town of Strawberry. Several miles up the hill from Strawberry look for the Beardsley Reservoir road dropping off to the left. On the Beardsley Dam Road go 1.2 miles to the first dirt road on the right (5NO9?). Go two miles on this road to an intersection for road 5NO9X. Left at this fork takes you down to the take-out. Right on 5NO9X takes you to the put-in 8.2 miles upstream. This 8.2 miles takes approximately 40 minutes to drive due to the rough surface but you'll never be bored because the views are incredible during this shuttle. Two wheel drive cars with high clearance can make it fine.
John Gangemi, 2002

Rapid Descriptions


No Gage

Gage Descriptions

This section would only flow when Donnells reservoir spills.

Minimum flows range from about 25 cfs up to 50 cfs. 

Oakdale and South San Joaquin Irrigation district maintain a gauge on this section (USGS #11292700).  At present information from this gauge is publicly available in the USGS annual reports which come out after each water year is over.  Historical flow information is available from 1956 to the present.  
Stanislaus River Basin pdf schematic showing reservoirs, diversions and gauges.

Directions Description

We have no additional detail on this route. Use the map below to calculate how to arrive to the main town from your zipcode.

No Accident Reports




Paul Martzen


Matt Muir


Revision #Revision DateAuthorComment
1195835 08/18/09 Paul Martzen
1194734 06/02/07 n/a n/a
1195524 06/22/09 Paul Martzen
1195769 08/13/09 Paul Martzen
1195836 08/18/09 Paul Martzen
1202816 10/31/13 Paul Martzen Minor formatting changes