This photo needs editing.
Difficulty III-V
Length 9.8 Miles
Flow Range 700 - 6000 CFS
Flow Rate as of: 2 hours ago 42 [CFS]
Reach Info Last Updated 04/05/2020 11:24 pm

River Description

Patterson Bend has a reputation as a hard run because of the old write up in the Holbeck & Stanley guidebook.    By modern standards it is a pretty moderate run.  Unfortunately, dependable flows are rare enough that boaters don't get a chance to see what it is really like. The scenery is outstanding and most of the rapids are in the class 3 range.  There are a number of wonderful class 4 rapids along the run, but only three class 5 rapids in Patterson Bend, plus two more down in the K1 to K2 section.   At moderate flows, all rapids are pool drop with long catch pools below.  

The first big caveat is that it requires work to do this run.   It requires work to paddle two miles across Kerchoff reservoir, then carry around the dam.   It is work to hike up to your car at the end.   It requires lots of work to get around Binocular Rapid if you choose not to run it.   It is easy to spend an hour or more if you portage.   It can take quite awhile just to scout. 

The second big caveat is that when this run does get spill, the flows are much more often high than moderate.  Also flows can fluctuate from moderate to high, quickly and frequently.  Most of the run is probably really good at high flows, but the big rapids pose serious issues for scouting, running or portaging. 

Prior to 1982 and the construction of the big Kerchoff #2 powerhouse, this section had dependable flows through the summer.   The old timers got to boat it a lot.   After 1982 flows became rare and it was nearly impossible to know when they occurred.   Since 1998 real time flow information has been available on the internet.   Now boaters can at least see when there is flow and how weird the patterns are.    If you want to boat this section it is best to go with the willingness to boat at whatever flow you get.   Fortunately the run is excellent over a wide flow range.  

Getting there: From Fresno, take highway 168 into the foothills. Turn left on Auberry Road to the town of Auberry. In Auberry, veer left onto Powerhouse Road at a fork next to the school. BLM Map of Patterson Bend area

Put-in: Follow Powerhouse Rd. to Kerchoff reservoir. Cross the bridge at the reservoir and go past the powerhouse. Launch at a nice beach.  Smalley Cove Campground has toilets and tables, but requires a fee to launch there. Paddle 2 miles across the lake to the dam. At the dam, take out at a small dock on the left and carry past buildings around the left side of the dam. A trail and stairways lead down to the river below the dam.   PG&E does not want the public passing through their facilities and may take steps to prevent access.  In this case, boaters will have to portage the dam on river right.   It is a shorter distance, but how difficult it may be is unknown at this time.

Take-out: From Auberry, follow Powerhouse Rd. just a few miles to a left turn onto Smalley Rd. There should be signs for the "San Joaquin River Gorge Recreation Area" which is owned by the BLM.   There are two options for the take-out at the recreation area.   You can take out at Kerchoff #1 powerhouse or 1.5 miles downstream at Kerchoff #2 powerhouse.   For either one you have to park on the road and carry your boats up a few hundred feet from the river.  For the #1 powerhouse park near the obvious junction.   Kerchoff #2 is further downstream so follow Smalley Rd. to the very end. A gate and some parking areas indicate that you are on top of the underground Kerchoff #2 powerhouse. From the right side (northwest) parking area look for a trail leading down to the river. It ends at the river a short ways upstream of the powerhouse discharge. You can also follow the gated road up from the river at the powerhouse outlet, but it will be less direct than the trail.

General Description: The first half of the run contains many long class 2, 3 and 4ish rapids seperated by long scenic pools. The scenery and geology are very interesting with types of rock not seen on other sections of the main San Joaquin. With decent access and dependable flows these few miles would be a classic and popular class 3 commercial float trip. Typical rapids through out the run tend to have distinct horizon lines that hide any view of the rapid until you you are speeding into it. At the halfway point, the gradient increases and the rapids get much bigger. Pools remain long, so rapids tend to be steep. There is a particularly ugly rapid near the halfway point that will be a portage for some and for most boaters at lower flows. It will be pretty obvious. Just past that, a beautiful section has 100 foot smooth, vertical cliffs on both sides of the river.

Binocular Rapid is the biggest rapid in the section and is visable from a few spots along the take-out road. On the river, it is difficult to get a good view of the whole rapid, so boaters must climb high above the rapid to get a good overview. One excellent overview is available by climbing high on river right. Some boaters have reported getting a good overview by climbing high on the left. Scouting near river level on the left means scrambling amongst monster boulders to get views of small sections at a time. At some medium flows the rapid is relatively straight forward, but at lower flows you may have to portage a portion or all of the rapid.  At flows around 7,000 cfs there appears be a river wide hole at the bottom.  Portage on left: through boulders (uhg!) to portage sections, or high on the hillside to portage the whole thing (uhg! uhg! uhg!). Scout it thoroughly and paddle as much as possible.

The first two rapids past Binocular are big and steep class 4 rapids.   Approaching the old powerhouse, the river enters a gorge of low, but vertical cliffs. There are a bunch of rapids in this section but they tend to be short, steep, pool drops.   The most busy and fun boating is probably from below Binocular Rapid to the powerhouse. The powerhouse can add up to 1735 cfs or so if it is running (much lower in recent years).  Three more rapids lead to the K1 to K2 Upper & Lower Falls, which are actually two separate class 5 drops.  The first is scouted and/or portaged on river right with high flows (on the left with flows of 1800 or less). A huge boulder blocks the channel forming huge holes on both sides. Ski jump the boulder to miss the holes at some flows. (At lower Autumn release of 1700 cfs one can run the very tight right side.) The next rapid is scouted on the right at all flows, but is very difficult to scout at spring spill flows because it is very hard to get out of your boat. Portage is extremely difficult at high spring flows and very difficult at low fall release flows. At high flows, run the left wall all the way down. (At fall release flows of 1700 cfs, ski jump or run the center falls, then get to the left channel and charge. A big hole at the bottom occupies 3/4's of the left chute. Punch it or swim.)

The final rapids ease off to the new powerhouse or into Millerton Lake.

Other Information Sources:
Kerchoff Project Relicensing Website
For more information about the SJRGRA see: SJGRA
Education program
The San Joaquin River Trail:  Effort to complete a 73 mile trail from Fresno to the Pacific Crest.
Information about Millerton Reservoir State Rec Area is available at Millerton SRA      

Temperance Flat Dam Proposal:

March 2014:  Bureu of Reclamation has issued a Draft Feasibility Report for a Temperance Flat Dam.   Please read and comment by October 27, 2014.

November 2014 Water Bond:  The California senate and legislatures have approved a bill which includes 3 billion dollars in bonds for construction of new water storage facilities.  Voters must approve the bond in the November 4 election. Temperance Flat is not named in the bond measure, but it is one of several potential projects that will compete for the bond funding.  Other potential projects include Sites Reservoir and groundwater storage projects.

Concurrently the Upper San Joaquin Basin Storage Investigation is now settling on the mile 274 dam proposal as being the most beneficial and feasible.    This dam site is slightly upstream of Sky Harbor and Finegold Creek.   The reservoir could hold 1.26 million acre feet of water and would extend back to the top of Kerchoff dam. 

Background:  This area of the San Joaquin is under study for several potential large dam and reservoir sites. See: Upper San Joaquin Basin Storage Investigation Three sites are under serious investigation. One site is about one mile upstream of the confluence with Finegold Creek and could have a maximum size of around 2.1 million ac/ft. One site is downstream of Temperance flat and could be as big as 2.7 million ac/ft. The third site is upstream of K1 to K2 about halfway through the Patterson Bend section. This would only contain 1.4 million ac/ft. Despite their huge sizes, the maximum annual yield from the biggest of these reservoirs is only 200,000 ac/ft. All of these reservoirs will bury the Patterson Bend section and depending on size, might also bury some or all of the Horseshoe Bend section. Maps from the study showing the sizes of the proposed reservoirs are available at the study website. A speech by Gary Bobker of the Bay Institute, gives some arguements against building new dams at these locations. Further information and links are at:

Friends of the River where you can write a letter to the governor.
California Water Myths: Virtual Tour  by UC Davis Center for Watershed Sciences.  

This research paper describes and discusses the astounding California flood of 1862. This flood was so big that the entire central valley was flooded and became a lake/river 300 miles long by 40 to 60 miles wide. Part of the problem was caused by hydraulic mining which released so much debri that the river beds in the valley were raised abnormally high. But the main cause was simply the incredible amount of rain and snow; such as 72 inches of rain in two months at Sonora. It seems possible that such volumes of water could  exceed the capacity of any additional reservoirs that we could reasonably build.

FERC information:
Federal Energy Regulatory Commission (FERC) links related to the Kerchoff Project, FERC project No. 96 This project was relicensed on Nov. 8, 1979. The license expires on Nov. 30, 2022.   The relicensing process typically starts about 6 to 8 years before the license expires.   To develop scheduled releases for this reach will require coordination with the upstream SCE Big Creek #4 project.  Scheduled releases could potentially occur in the fall during scheduled maintanence as well as in spring or summer.     

The generators at the two powerhouses have a rated maximum capacity of 174,075 KiloWatts.
Search for FERC documents related to Kerchoff at
In the Docket Number box, write P-96-* to do a wild card search for any documents related to Project 0096.

Minimum Instream Flows: are 25 cfs year round, but somewhat higher flows must be released in order to keep water temperature below 27 degrees.

Paul Martzen, 2003



Rapid Descriptions

Smalley Cove

Class - Mile - 0
Rapid Thumbnail Missing
Campground at Kerchoff Reservoir. Picnic tables and pit toilets. No potable water. It is about a mile and three quarters down the reservoir to the dam. The scenery is nice and makes one wonder what the river canyon was like underneath the reservoir.

Kerchoff dam

Class - N/A Mile - 1.77

There is a dock on the left, that provides an easy take out.   Carry around the left side of the dam on walkways and stairs. The stairs end before reaching the pool at the base of the dam.  The last bit is scrambling down over steep boulders.   There is also a bit of poison oak and some berry bushes guarding the scramble.  The total portage distance is about 330 yards. 


Launch point

Class - III+ Mile - 1.9

Launch wherever is convenient below the dam.   The eddy current in the pool at the base of the dam will be very strong.  Class 3 rapids start immediately and extend for 2/10 of a mile.   Though moderate these rapids will probably wake you up and give you a good sense of what is below.  

640 feet elevation approximately


Class - II Mile - 2.8

A long island divides the channel. Silt from the reservoir spills into the river and settles in the flat stretches of the first half of the run.  The silt provides footing for trees and brush.   Here the trees and brush grow completely across the river, though in a long, right to left diagonal.   The river has small openings at each end of the island.  The upstream opening is bigger and leads to a more gradual drop.   The downstream opening is very small and has a steeper more junky drop. 



Class - III Mile - 3.7

This is probably a class 3 to 3+ rapid.   Trees block the view at the top, but scouting is easy from either side.    There is a wide easy entrance through the trees then a couple of strong laterals slap you around.   There is a hole or pour over to avoid at the bottom


Mike Walker Canyon

Class - Mile - 3.9
Rapid Thumbnail Missing
A private dirt road is visible on river right.

No Name

Class - N/A Mile - 4.12
Rapid Thumbnail Missing

River starts bending to the south.

Grapevine Canyon & Rapid

Class - III Mile - 4.44
Rapid Thumbnail Missing

The river is gradually bending straight south.   I can't remember how big the rapid is, maybe class 3.


Class - Mile - 5.4
Rapid Thumbnail Missing
River heads slightly southwest.


Class - IV Mile - 6.3

This is the biggest rapid in the easy half of the run.   A wide horizon line makes it hard to decide where to enter.  Scout  river left.  In the middle of the rapid, rocks clutter the middle and right side.   A steep and powerful but clean chute remains on the left.   Deal with the hydraulics then decide where to exit.   At 1200 cfs the exit (pictured) was particularly congested with ledges and rocks.   At higher flows they will be impressive holes. 

No Name

Class - Mile - 6.34
Rapid Thumbnail Missing
River heads East. Numerous rapids.

First Five

Class - V Mile - 7.9
Rapid Thumbnail Missing

First Five should be obvious by the steeper wall on the right and the huge boulders on the left.   The safest route is down the right, but it can get too junky as flows drop.   Portage around the boulders on the left.     There is a decent pool between here and El Limpo.

El Limpo

Class - V Mile - 8

Big rapids start around this point. The second one is junky at lower flows and will be a portage for many boaters.   The rapid has several steep drops  with some constrictions in the first or second drop.    There is a low water portage route against the right wall that probably also serves as a high flow sneak route. 



Class - IV Mile - 8.2

The next rapid following El Limpo turns out to be an easier rapid.   Boulders on the right constrict the river to a narrow drop on the left.  Then paddle back to the right and punch two ledge drops.


A long beautiful pool follows this rapid, then 3 moderate rapids lead to Binocular Rapid.

Binocular rapid

Class - V Mile - 8.6

A big long rapid.  Scouting views can be had from both high on river right or left.  The right side gives a more unobstructed view.  Depending on flow and paddler, all or part may need to be portaged. Portage on river left with great effort. Sometimes only a portion needs to be portaged and that may be accomplished at river level.

Elevation approxitmately 720 feet.

Below Binoc

Class - IV Mile - 8.9

The first two rapids below Binocular are big and stompy, but only class 4ish.   They might deserve a scout on your first meeting, or you can drop in with faith and courage.   


There are a large number of rapids between here and the old powerhouse, so they come pretty quickly, seperated by short sections of flat water.  Several are short but vertical drops.  Most of them punch pretty good.   Class 3 to 4.

Kerchoff #1 powerhouse

Class - N/A Mile - 9.8
Rapid Thumbnail Missing

The powerhouse is on river left and presents an escape route if needed. It can add another 850 to 1700 cfs into the K1 to K2 section if it is running. See the pictures and descriptions on that page.   A PG&E road leads down to the powerhouse, but it is gated at the top.   From the river up to the road is steep and awkward but short.  From the powerhouse up to the gate on the road is almost a half mile with a couple hundred feet of elevation gain. 

640 feet elevation.

Upper Falls

Class - V Mile - 10.4

A huge boulder spans the river channel.   At flows below 2,000 cfs there is a river level scout and portage route on the left.  At higher flows scout from river right.   

Lower Falls

Class - V Mile - 10.5

At most high flows the usual route is down the left side.  Scouting is not easy here and portaging is very difficult.   It is safest to scout the Upper and Lower Falls by hiking directly down hill from the BLM area trailhead and campground.   It is a steep hike down to the river, but not a very long distance.

Kerchoff #2 Powerhouse

Class - N/A Mile - 11.54
Rapid Thumbnail Missing

This powerhouse is underground so you will only see the outlet on the left and a road coming down to the top of this outlet.   You can duck under the fence at the left side of the outlet and walk up the road to the parking area.   The walking distance is about 3000 feet.   Alternatively you can hike up a fisherman's trail about 30 or 40 yards to the left (upstream) of the outlet.  The hiking distance is only about 700 feet, but its steep.  During most seasons when Patterson Bend is runnable, Millerton Reservoir will be high and you will be paddling on this lake by the time you reach here.


default user thumbnail
Richard Penny
10 years ago

I remember joining Paul on Patterson Bend in the mid-1990's. Ours may have been one of the earliest trips after the first descent by the Holbeck and Stanley crew years prior. We attempted to portage Binocular through the boulders and poison oak on the left, wearing drysuits in the horrible heat. "Ugh" as Paul puts it in the river description. So we ran the second two-thirds or half of the rapid, not because we wanted to, but because the alternative was heat stroke. Richard

Gage Descriptions

San Joaquin - At Patterson Bend
Show 30 Days ------------- Show 3 Years


Patterson Bend is boatable at a pretty wide range of flows.  The rapids are probably the cleanest at higher flows of 3,000 or 4,000 cfs.   Some paddlers might like it at even higher flows.  At the low end, most of the run is still excellent at 700 cfs, though 3 rapids must be portaged.   

In the spring of wet years, Patterson Bend often gets spill flows, but they are usually very erratic.   Flows can be high one day and off the next, then back on.   If boaters are willing to accept whatever flow there is, then there are a fair number of paddling opportunities.   If one waits for an ideal moderate flow window it is almost impossible to catch this section.   In 2009 and 2010 there were flows for several weeks in the fall.  Flows were highly variable from hour to hour, but mostly within a moderate to low range.

Flows in this reach are diverted by Kerchoff dam. The minimum instream flow released from this dam is mandated to be 25 cfs all year round. Actual minimum flows tend to be a 10 or 20 cfs higher. Optimum boating flows are probably between 1000 and 5000 cfs. Boatable flows are generally only available during the peak runoff of wet years, but sometimes they also occur in late October or November related to powerhouse maintanence. Flows tend to vary dramatically from day to day when it does spill. This section has a much shorter and more erratic flow season than the upstream HorseShoe Bend reach.

The gauging station is a short ways downstream of the dam. If you see this gauge, look at the numbers on the staff gauge and make a note of where the water level is. When you get back home you can translate that water level to cfs with this Rating Table
See also CDEC gauge info, CDEC, and Dreamflows.  Historical records are available at USGS #11246700.  

The PG&E powerhouse that dewaters this section is Kerchoff #2.  It can divert up to 5,000 cfs.  Historical daily flow records for this powerhouse are available from USGS #11247050.   Historical daily flow records for the old PG&E powerhouse, Kerchoff #1 are available from USGS #11246950.

The last few miles of this section often have dependable flows every Autumn. Millerton Reservoir drops low enough every fall to reveal as much as 3 miles of river below a big underground powerhouse, Kerchoff #2. This powerhouse can release up to 5,000 cfs into the Millerton Bottoms section.

Then, typically in late October and November, the big powerhouse turns off and an older, smaller powerhouse, Kerchoff #1, comes online releasing water into the 1.9 mile, class 5, K1 to K2 section. In the past, flows from this powerhouse were typically around 1700 cfs, but in recent years, flows have been lower, around 800 or 900 cfs.    Since 2010, outflows from the powerhouse have been in the 500 cfs range.   The lower capacity of the old powerhouse in recent years has allowed boatable flows in Patterson Bend in the fall. 

The Patterson Bend gauge, linked above varies wildly at times. Even more wildly than seems possible, but PG&E assures us that the gauge is correct.  The following flow information sources can provide some corroboration or correction, but only for looking at previous days flows. Millerton Average Daily inflows, Real Time Reservoir Levels, DailyReport - pdf      


Some of the highest flows in this reach in recent years were during the January 1997 floods.   CDEC has Hourly Inflow to Millerton records for this period.    According to the Friant office of Bureau of Reclamation there is some possibility that a new gauge will be installed at the upper end of Millerton to measure inflows.   It would be a few years off if this did happen (as of 2010). 

Directions Description


No Accident Reports



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Spill Cessation Horseshoe Bend - San Joaquin River (CA)

Theresa Simsiman

American Whitewater, San Joaquin Stakeholders and Agencies have negotiated with Southern California Edison to test better management of naturally occuring spill.  During the last spill of this season SCE will test slowing down the rate of reducing flows. This more natural flow regime benefits the native aquatic species while still providing whitewater boating opportuniites and is referred to as spill cessation.

While we had hoped to see this test in August, mother nature had other plans!  SCE has informed us that the last anticipated spill for the seasons is happening earlier than anticipated and they will start their test this week. So start making your boating plans now!

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American Whitewater Opposes Temperance Flat Dam (CA)

Megan Hooker

American Whitewater submitted comments this week to the Bureau of Reclamation in opposition of the proposed Temperance Flat Dam slated for the San Joaquin River in California. The proposed dam would inundate a reach of river that the Bureau of Land Management recognized as suitable for inclusion in the National Wild and Scenic Rivers System for its cultral and scenic values. Temperance Flat Dam will have steep economic and resource costs while yeilding little water, and is not the solution to California's extreme drought.


Paul Martzen


Theresa Simsiman


Revision #Revision DateAuthorComment
1203184 03/19/14 Paul Martzen Linked to Dam studies
1214584 04/05/20 Paul Martzen updated description
1209914 06/20/18 Theresa Simsiman Remove offensive name as requested by the tribe
1196857 12/10/09 Paul Martzen Added link to UC Davis water tour
1190082 08/23/08 Paul Martzen n/a
1196425 11/05/09 Paul Martzen Dam proposal update, minor corrections
1196265 10/16/09 Paul Martzen
1196269 10/16/09 Paul Martzen
1198407 10/17/10 Paul Martzen link to 97 flood, hourly records
1198565 11/05/10 Paul Martzen minor updates
1198567 11/05/10 Paul Martzen update rapids
1200348 07/03/11 Paul Martzen Added rapids, photos and minor corrections
1201870 02/26/13 Paul Martzen Added USGS links
1203727 10/14/14 Paul Martzen Temperance Flat Dam - update
1205891 03/03/16 Paul Martzen put in change
1211384 03/09/19 Paul Martzen updated description