southforkboise.org blog

The above illustration is from the report Genetic evaluation of...

Mon, 16 Nov 2009 02:27:52 -0500

The above illustration is from the report Genetic evaluation of population structure and individual movement of rainbow trout in the lower South Fork Boise River and associated tributaries and the report (pdf) is available by clicking on it.

November 12th Meeting to Highlight South Fork Boise Genetics Study

Sun, 08 Nov 2009 00:31:00 -0500

Make plans to attend an open joint meeting of TU and Boise Valley Fly Fishermen on Thursday, November 12, 2009 at the Boise Public Library to see a presentation on the genetic profile of the South Fork Boise River (SFB) fishery as well as hear a panel discussion of agency and angling community perspectives on Southwest Idaho’s greatest fishing water. Doors open at 6:30 p.m. and the program will begin at 7:00 p.m. Enter in the doors on the 8th Street side at the southwest end of the building.

Helen Neville with the TU national science team based in Boise will present her findings based on the laboratory analysis of the genetic information sampled from more than 300 rainbow trout, and compare that information with dozens of wild trout populations in the North and Middle Fork Boise Rivers.

Idaho Fish & Game, the Boise National Forest, Bureau of Reclamation, TU and BVFF worked together in 2008 to sample the SFB fishery and adjacent tributaries to gather genetic information on redband or rainbow trout. The information presented November 12 will provide a foundation by which a conservation strategy for the SFB fishery could be developed.

Contraindications in the Upper Watershed The first month of the...

Sun, 01 Nov 2009 17:07:00 -0500

Contraindications in the Upper Watershed

The first month of the 2010 water year is done and there is one interesting development in the South Fork Boise River. During October the flows upstream of Anderson Ranch Reservoir were higher than last year (see alternating graph above). The blue line (it’s hard to see) was higher through the month owing to the big storm that blew across the northern Rockies in early October. Trinity Mountain supposedly has 25 inches of snow. So, as that snow melted the meter at Featherville recorded a higher flow than October 2008.

A cooler and wetter October actually helped fill Anderson Ranch Reservoir. The amount it trivial compared to a normal spring run-off of snowpack, but today Anderson Ranch has 268,000 acre feet stored about 5,000 acre feet more than at the beginning of the month. Usually October is a month where the 300 cfs flows from Anderson Ranch Reseer starts to pull on the storage. This year it was different.

SFB electrofishing discussed on westfly.com board

Sun, 25 Oct 2009 00:43:29 -0400

SFB electrofishing discussed on westfly.com board

IDFG Electrofishing South Fork Boise

Thu, 15 Oct 2009 17:32:08 -0400

IDFG crews are on their marking run this week on the South Fork Boise River. They were to complete the first phase during Tuesday and Wednesday, and then come back next week for the recapture run.

See the little blue tick mark, just below the red line? ...

Tue, 06 Oct 2009 20:09:57 -0400

See the little blue tick mark, just below the red line? That’s where we are as far as water in Anderson Ranch Reservoir so far this water year (water years start October 1st, just like the Federal Fiscal Year).

We start this water year near the average and pretty well ahead of last year. And the Snotel site at Trinity Mtn. had 25 inches of snow this morning. Much of that should melt this month, and soak the ground pretty well. Good start to the fish and float opportunities in 2010.

Flows drop to 300 cfs

Fri, 18 Sep 2009 00:44:45 -0400

Flows drop to 300 cfs

Flows from Anderson Ranch Dam are now at the wadeable 600 cfs.

Sun, 06 Sep 2009 00:59:41 -0400

Flows from Anderson Ranch Dam are now at the wadeable 600 cfs.

Anderson Reservoir is draining at the same rate as last...

Sat, 22 Aug 2009 00:49:27 -0400

Anderson Reservoir is draining at the same rate as last year.

Flows should step down at about the same time as last year in the coming weeks. Look for 600 cfs soon.

The Boise River reservoir system overall is carrying more water than at this time last year.

Flows from Anderson Ranch Reservoir are now at the...

Sun, 28 Jun 2009 12:52:35 -0400

Flows from Anderson Ranch Reservoir are now at the “normal” summer discharge. Anderson Reservoir will now slowly begin to empty, and the drawdown will increase through the summer.

Flows at the Featherville gage fell below last year’s...

Sun, 28 Jun 2009 12:49:49 -0400

Flows at the Featherville gage fell below last year’s flows for the 2nd half of June. So much for the earlier post and predictions.

Snow is melted from the Trinity Mtn. station. 2009 was below...

Sun, 28 Jun 2009 12:45:00 -0400

Snow is melted from the Trinity Mtn. station. 2009 was below the average of the 1971-2000 period, but total precipitation was slightly higher.

Group photo at the South Fork Boise River clean-up as part of...

Tue, 16 Jun 2009 02:32:40 -0400

Group photo at the South Fork Boise River clean-up as part of the Trout Unlimited national stream clean-up day.

Flows at Featherville on the upper South Fork Boise have settled...

Mon, 15 Jun 2009 01:17:09 -0400

Flows at Featherville on the upper South Fork Boise have settled to about 2,300 cfs and are slightly lower than at this time last year. However, with Anderson Ranch Reservoir at 99 percent full you can expect water managers to pass all inflows and keep the lower SFB at higher flows for quite some time.

The amount of snow remaining on Trinity Mountain can be a useful...

Tue, 09 Jun 2009 17:14:00 -0400

The amount of snow remaining on Trinity Mountain can be a useful indicator of how much water is expected to flow into the upper South Fork Boise River and thence American Falls Reservoir.

As the above chart indicates, there is less snow remaining on the mountain than last year. Anderson Ranch is full but it appears that future flows into the reservoir through the month of June will continue to drop.

NEVER MIND - Flows dropping like a rock. Saturday’s post...

Tue, 09 Jun 2009 15:20:07 -0400

NEVER MIND - Flows dropping like a rock.

Saturday’s post contains one error showing snowpack at Trinity Mtn. Snotel site and June flows: total snow depth was used instead of Snow Water Equivalency. The above chart shows flows dropping like a rock. We will post an updated chart of remaining snow as compared to last year.

HOW LONG WILL HIGH FLOWS LAST IN THE SOUTH FORK BOISE? Yesterday...

Sat, 06 Jun 2009 23:38:00 -0400

HOW LONG WILL HIGH FLOWS LAST IN THE SOUTH FORK BOISE?

Yesterday we displayed the above chart and noted the flow spike - discharge from Anderson Ranch Dam is at 3,500 cfs, nearly double last year’s summer flow of 1,800 cfs (old timers remember the normal summer flow at 1,600 cfs and in a future post we will report whether 1,800 cfs is the “new normal”).

Today we ask how long will these high flows persist in the South Fork Boise River? Anglers will no doubt want to know when safer, slower flows will return.

First, let’s examine the chart above. Take note that the flows throughout June 2008 were 600 cfs as Anderson Ranch Reservoir filled. What’s different this year?

One thing different than last year is Anderson Ranch Reservoir...

Sat, 06 Jun 2009 23:35:26 -0400

One thing different than last year is Anderson Ranch Reservoir is already filled to capacity. The chart above illustrates this year’s contents in the reservoir as compared to last year and to the long term average. Last June the reservoir was still filling and that’s why flows were at 600 cfs through the month.

So we know Anderson Reservoir is full and whatever will flow...

Sat, 06 Jun 2009 23:34:00 -0400

So we know Anderson Reservoir is full and whatever will flow into the pool from the upper South Fork Boise River and minor tributaries will have to leave the reservoir.

The above chart shows this year’s flow at Featherville compared to last year’s. For whatever reason no long-term average flow is shown, which is too bad because this year looks like an average year. Nonetheless we know this year’s flow is higher than last year, and for the coming weeks what comes in will have to go out of the reservoir.

So what’s a guess on flows for the next month? We will use the end of May level of snow at Trinity Mountain as a proxy.

The Snotel site indicates 46 inches of snow water at Trinity....

Sat, 06 Jun 2009 23:33:00 -0400

The Snotel site indicates 46 inches of snow water at Trinity. The chart above shows about 50 years of data on the amount of snow pack at the end of May at this site, correlated with average water flows in June in the South Fork Boise at Featherville. Trinity snow pack is not a perfect predictor, but the correlation values are respectable. The 46 inches is the red data point, and as shown the average flow for June projects to be around 2,600 cfs, assuming the regression line is an accurate estimate for this year. Last year’s snow pack/flow data point is green. The past five days the flows have been 3,500 cfs. Flows have probably peaked in the past few days and should begin to drop through the month, but flows will most likely easily exceed 2008 flows through June. All the snow that still has to melt will have to pass through the reservoir since it’s full.

Conclusion: Think you’ll be wading soon? Forget it. How about those “normal” flows of 1,600 cfs or 1,800 cfs? Probably not. ~~Best to expect flows in the South Fork Boise below Anderson Dame to remain above 2,000 cfs for the rest of the month.~~ Based on updated data we will see flow settle in the coming days in the range of 2,000 cfs. The above chart was based on snowpack but not water equivalent inches and there is less water than at first thought. See updated chart above that shows snow water trends at Trinity Mtn.