[LTER-mcm-pi] wait... there IS more variability in streamflow since 2002!

Mon Aug 17 02:10:24 MDT 2015

Hi Mike - we have a paper in review right now on freeze-thaw cycles and soil moisture.  If I recall correctly, we showed that soil moisture has been increasing (not sure about variance around the mean), but we do show an increase in magnitude and variance of freeze-thaw cycles in soils.  Matt’s on vacation now but Diana will have him send those data when he gets back next week.
-b

On Aug 17, 2015, at 9:17 AM, Michael Gooseff <Michael.Gooseff at Colorado.EDU<mailto:Michael.Gooseff at Colorado.EDU>> wrote:

Hi Jeb,

Attached is a short ppt with figures I showed at the 2013 MCM science mtg in Boulder with a title slide that has some explanation.  Bottom line (analyzed through maybe 2011 at the time) is that high flows on individual streams (e.g., the 90th percentile for a given season) are higher than in the past.  That makes sense if flows are increasing overall.  BUT, we haven’t looked at the frequency of flows in each season (I.e., an analysis of the flow magnitudes in a season) to see if those are changing much.  That might be fairly easy.  Let me pose that analysis to Adam and Chris and see what happens…

Cheers
-Mike

From: John Barrett
Date: Sunday, August 16, 2015 at 2:56 PM
To: Michael Gooseff
Cc: "mcm-pi at lternet.edu<mailto:mcm-pi at lternet.edu>", Berry Lyons
Subject: Re: [LTER-mcm-pi] wait... there IS more variability in streamflow since 2002!

OK, so as a total block of time. What about the variance within a flow year. Has that changed over time too? Basically the distinction is between seasonal and inferannual variability.
On Aug 16, 2015 6:17 PM, "Michael Gooseff" <michael.gooseff at colorado.edu<mailto:michael.gooseff at colorado.edu>> wrote:
It’s the annual variance of the total flows.  So, we grouped the total annual flow volumes from 1990-2001 and from 2003-2013 then calculated variance on both groups.

Mike

From: John Barrett
Date: Sunday, August 16, 2015 at 2:08 PM
To: Michael Gooseff
Cc: Berry Lyons, "mcm-pi at lternet.edu<mailto:mcm-pi at lternet.edu>"
Subject: Re: [LTER-mcm-pi] wait... there IS more variability in streamflow since 2002!

Really cool mike. That's certainly the general impression.
Is the increase in variance a within year phenomena or interannual?
On Aug 16, 2015 4:56 PM, "Michael Gooseff" <michael.gooseff at colorado.edu<mailto:michael.gooseff at colorado.edu>> wrote:
Hi all,  (greetings from Toolik)

I wanted to follow up on a conversation we had a few months ago about the variability in the MDVs since 2002.  Recall that Chris shared with us a spreadsheet of annual flow volumes from the Fryxell basin streams, and that the analyses suggested that variance had gone down in the 2003-2013 period (compared to 1990-2001).  My recollection is that this sort of took the wind out of our sails on that discussion.

I revisited these analyses in the past week in trying to get some writing and a figure together for the Bioscience paper that Andrew is leading and Chris and I revised the analyses -

  1.  We fixed an error we found in the calculation of % change of variance from pre- to post-flood.
  2.  We took out the 2001-02 flood year (to look at ‘before’ and ‘after’, we argue that we shouldn’t lump the flood year in either if we postulate that it is a turning point)  —> doing these 2 steps alone resulted in an increase of variance of 185% in the post-flood vs pre-flood period…
  3.  However, we had several seasons in each period of poor or no flow estimates because of technical problems with gauges or controls (3 in the pre-flood period (~4%), 7 in the post-flood period (~7%)).  Chris came up with some nice correlations to fill in these gaps (no relationship has an R2 < 0.70), and the result is an increase in variance of 48% in the post-flood period vs. the pre-flood period.  This is (I think) our best analysis of the flow records and indicates increased variance in the recent decade.  (most updated figure inserted below with snip of text)

So, I’d like to suggest that we revisit the notion that our system is becoming more variable as we emerge from the cooling trend as a potential theme for the renewal.  What are some of the other ecosystem parameters we might evaluate for similar changes?
—> JP showed us UW PAR data last week that looks like it could be more variable, but will be hard to evaluate with the gaps
—> Soil or Air temperature analyses?
—> Soil moisture analyses from a long-term plot?
—> chl-a in lake photic zone?

If we can demonstrate change in ecosystem temporal trends (the synthesis paper mega plot) and increased variance of some drivers, I think we have an easy sell on the motivation for the proposal…

Talk to you all on Thursday.

Cheers
-Mike

Snip of text:  [in the pre-flood period] mean annual streamflow was 0.85 x 106 m3 with a standard deviation of 0.93 x 106 m3 and a variance over this period of 0.86 x 109 m3.  The highest annual flows on record were observed in the 2001-02 flow season (total streamflow over 5 x 106 m3).  Since this ‘flood year’, mean annual discharge has increased (2003-2013; 1.59 x 106 m3), as has the standard deviation (1.13 x 106 m3) and the variance (1.28 x 109 m3, an increase of 49%).
<A5029176-02CE-4C56-8D60-60E7C7B196AD.png>

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Michael Gooseff, Associate Professor
Institute of Arctic and Alpine Research
Civil, Architectural, and Environmental Engineering
University of Colorado
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email: michael.gooseff at colorado.edu<mailto:michael.gooseff at colorado.edu>
web: http://goosefflab.weebly.com<http://goosefflab.weebly.com/>
phone: 303.735.5333<tel:303.735.5333>

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