The 2013 Weak Water Year

We grabbed a few charts at the end of Water Year 2013 to put some perspective on the water situation.

Flows from Anderson Ranch Dam:

Flow From Anderson Ranch Dam where blue line = 2013, green line = 2012, red line = long-term average

The summertime flows were 1,600 cfs instead of 1,800 cfs in 2012.  The 1,600 cfs flows extended well into August to provide irrigation water to users in the Treasure Valley.  The rest of the system was draining so more water was moved from Anderson Ranch pool.  And you can see what happened in the reservoir here:

Water stored in Anderson Ranch Dam blue line is 2013 and green line 2012 and long term average is the red line

Anderson Ranch reservoir started the water year (October 2012) very near the average for water in the pool.  The low snowpack in the winter meant less runoff into the pool in the spring and early summer.  The peak amount of water in May was nowhere near the average, let alone filling Anderson Ranch.  The the 1,600 cfs flows pulled the contents to an amount well below average and at a high rate until mid August.  The water year ends with 100,000 acre feet in the pool.

The reservoir drained very quickly because it was a year where much less water flowed into Anderson Ranch Reservoir as seen in the chart for the water gage at Featherville:

Water flows on South Fork at Featherville gage with 2013 in blue, 2012 in green and average in red

So the blue line in the chart above shows just how below average the flows were upstream of Anderson Ranch pool.  By the way, the spike in river flows in late April 2012 on the green line is a same time when a record flow was observed in the Middle Fork Boise River at Twin Springs gage.  Some readers may recall the late April heavy rains that  melted much of the lower to mid elevation snow into the South Fork Boise River.

One indication of the water year ending in a whimper is what happened with the flow gage on the South Fork Boise a mile or so downstream of Anderson Ranch Dam:

River flow data in late September 2013 was affected by the landslides into the South Fork Boise

The slides on September 12, 2013 knocked out the water gages for a few days.  They are back running now, but the chart above from September 24 shows only a brief period when it was working that day and no data was charted for previous days.  This situation is understandable given that much debris tumbled into the South Fork and it may have directly affected the functioning of the gage or perhaps changed the profile of the channel in the area of the gage making a clean reading of water flows a challenge and thus a need to recalibrate the equipment.  The automated system for this gage is working as shown on the USGS gage here.

Looking forward, there have been some inquiries and informal discussion whether it would be possible to shape flows from Anderson Ranch Dam in 2014 to deal with the debris and sediment in the South Fork Boise River to help transport the sediment and allow the river to carve a channel through the massive deposits in the river.  For any of this to happen it will require water in Anderson Ranch pool that is not yet there.  A winter with above average snow could be very important to developing some alternatives to shape the flow releases, their timing and magnitude, and it will have to happen without adverse effects on downstream water users.  But readers may be interested in knowing it is a topic of conversation, or at least was prior to the government shutdown.


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Flows drop after a long pull on Anderson Ranch Water


South Fork Boise River flows downstream of Anderson Ranch Dam

The Bureau of Reclamation began turning down the dial on the boating flows after the end of the Labor Day weekend.

By the end of Tuesday September 4th flows dropped from 1,850 cfs to 900 cfs.  On Wednesday the 5th the flows were at 600 cfs.

Summer boating flows lasted longer and were slightly higher than the typical 1,600 cfs.  In fact, the 1,800 cfs flow seems to be a “new normal.”

So why did flows stay higher through Labor Day?  Continue Reading…

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Flow management and stranding juvenile trout: what we know and don’t know, and what it means

If you are interested in helping study the effects of the South Fork Boise River flow changes on the wild trout fishery in September, read more below and contact us with your availability.

For several years the South Fork Boise River wild trout fishery has been getting significant attention from a number of sportsmen, state and Federal resource agencies.  You reading this website story is just one example.  River flow changes and effects on the aquatic system has gained attention with angler concerns about potential adverse effects on juvenile rainbow trout and macroinvertebrates (aquatic insects that provide a food base for trout), when Anderson Ranch Dam flows are routinely ramped down to 600 cfs and 300 cfs as irrigation storage releases are ended in September.

Whitefish Ed in his formal fishing dress on the banks of the Henry's Fork (photo from westfly message board)

Back in November 2009 interested anglers and agency staff met at the Boise Public Library to hear about a genetic study of the South Fork Boise River fishery.  During a panel discussion several topics came up, including flow management.

Could the Bureau of Reclamation do something to change their flow management?  There was no answer to that question, but the topic did stick with one local angler who goes by the handle “Whitefish Ed” on the westfly.com message board.

Ed initiated his own study and looked at the SFB on September 15, 2011, a few hours after the flow dropped from 600 to 300 cfs, and observed many stranded wild juvenile trout along the river’s shoreline in three locations.  You can find Ed’s story at this westfly.com message thread which is worth the read.  Ed’s writing style is as colorful as that shirt he is wearing in the photo

After some meeting this spring with state and Federal agency biologists a plan has Continue Reading…

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South Fork at 6,000 cfs: A Top Ten Rating

On Friday April 27, 2012, releases from Anderson Ranch Dam hit 6,000 cfs.  This is a flow quantity rarely seen on the South Fork Boise River.  Based on records dating back to 1943 (seven years before the dam’s completion) here’s the top years where peak flows got nearly to, or exceeded, 6,000 cfs.

Since 1943 here are the years where peak flows were 6,000 cfs or better

Continue Reading…


Waiting for 300 cfs

Word on the street, or should we say stream, is that the flow releases out of Anderson Ranch will drop to the minimum 300 cfs flows on or around September 15.  You can keep an eye on our handy Current Conditions page, or access the other websites with the flow graphs.  Specific date aside, we know for certain there is a lot of water in Anderson Ranch, and we it appears La Nina is Back – which could mean another year of favorable winter snowpack in the Pacific Northwest.