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

[Andrew Fountain]

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> 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%).
>
>
> -=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-
> 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
> web: http://goosefflab.weebly.com
> phone: 303.735.5333
>
>
> _______________________________________________
> Long Term Ecological Research Network
> mcm-pi mailing list
> mcm-pi at lternet.edu
>
>


-- 
Andrew G. Fountain

Department of Geology
Department of Geography

Address:                            FedEx/Shipping Address:
------------------------                 --------------------------
Department of Geology        Department of Geology
Portland State University      17 Cramer Hall
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                                          Portland, OR 97201
Email:  andrew at pdx.edu      USA
http://www.glaciers.pdx.edu
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