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

Mon Aug 17 05:16:28 MDT 2015

I seem to recall a difference in the pre and post flood year variability in upper lake temperatures in the analysis we did a few years ago as well. I will check.

Andrew, we can include any met variability analysis to the group in our presentation of the summaries in Boulder. Mike has now created a slot for met which was missing. I'll talk to Maciek when he's in BR this week

-Peter 

> On Aug 16, 2015, at 6:58 PM, Andrew Fountain <andrew at pdx.edu> wrote:
> 
> Mike,
> 
> Is the variance higher because the flow is higher after the flood year?  Did you do a coefficient of variation analysis?
> 
> Maciek is working on air temp and soil temp.
> 
> Andrew
> 
> On Sun, Aug 16, 2015 at 1:55 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%).
> [cid:A5029176-02CE-4C56-8D60-60E7C7B196AD]
> 
> 
> -=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-
> Michael Gooseff, Associate Professor
> Institute of Arctic and Alpine Research
> Civil, Architectural, and Environmental Engineering
> University of Colorado
> Boulder, CO 80309-0450
> 
> 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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> 
> --
> Andrew G. Fountain
> 
> Department of Geology
> Department of Geography
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