Tuesday, April 10, 2012

3297.txt

date: Thu, 10 Apr 2008 06:52:00 -0600
from: "Joel Smith" <JSmithatXYZxyzatusconsulting.com>
subject: RE: longterm river flow (2)
to: "Phil Jones" <p.jonesatXYZxyz.ac.uk>, "Tom Wigley" <wigleyatXYZxyzr.edu>

HI Phil

Thanks and that's very interesting. We did something similar in Boulder, Colorado. A few
years ago the city looked at its vulnerability to a 300 year reconstruction by Connie
Woodhouse (then of NOAA, now at the University of Arizona). We combined a new 400+ year
reconstruction with GCM output. We derived proxy temperature and precipitation in the
reconstruction by matching reconstructed flow years with "nearest neighbors" in the part of
the reconstructed flow record that overlaps with observations. We then applied the monthly
changes in precipitation and temperature from a wide range of GCM output.

In this case the combination is very interesting. Boulder has low vulnerability to the
reconstructed flows (with regard to drought). It also has low vulnerability to the
imposition of climate change on the historic observed climate record. But, the combination
of GCM output and the reconstruction can cause more frequent violations of drought criteria

yours,

Joel

Joel B. Smith
Stratus Consulting Inc.
P.O. Box 4059
Boulder, CO 80306-4059 USA
Tel: 1-303-381-8218
Fax: 1-303-381-8200
jsmithatXYZxyzatusconsulting.com
www.stratusconsulting.com
______________________________________________________________________________________

From: Phil Jones [mailto:p.jones@uea.ac.uk]
Sent: Thu 4/10/2008 2:38 AM
To: Tom Wigley
Cc: Joel Smith
Subject: Re: longterm river flow (2)

Tom,
The EA work in 2006/7 resulted in 3 EA reports and 3 summaries.
I can't find the first referred to in Jones et al 2006 as Cole and
Marsh (2005).
This one that I don't have is mainly placing recent droughts in a
longer context
with EWP and other long rainfall and groundwater level series.
In this report we took the riverflow reconstructions from the 2006 paper
in IJC (for the River Eden nr Carlisle and the River Ouse to Denver Sluice).
We used these reconstructions to approximate inflows to reservoirs on
the Ouse catchment and in the Lake District (Eden).
The relevant Water Authorities then used their resource models with
daily inflows to see how their systems responded to flows over the last 200
years. To get daily flows, we had some modern records, so we took monthly
daily sequences with roughly the same mean flows as reconstructed at the
two gauging stations. As there was between 20-50 years of daily flows, there
was some repetition of sequences to cover the 200 years.
We then rerun the whole process with several futures from 3 RCM
simulations
(chosen to be from 3 different driving GCMs (HadCM3, ECHAM4 and Arpege).
These changes to rainfall and T were applied to the whole sequence
for 200 years,
so combining a 'future' with the long historic record which
encompassed natural
variability.
The 'future' precip changes were applied directly to the historic rainfall
sequences, For future actual evapotranspiration (required by the statistical
rainfall/runoff model) I developed a simple water balance model, based
in rainfall and temperature. Modified temperature produced monthly sequences
of Thornethwaite PET, which then produced modified AET from the simple
water balance model.
The Wade et al reports then look at implications for the two
Water Authorities.
The historic droughts in the 19th century (with modern
abstractions) were sometimes
worse (particularly on the Ouse) than recent droughts. These didn't
get much worse in the future as winter rainfall went up in the RCMs, and the
catchment has a long memory. Future droughts got worse in the Lake District
as summers got drier and here the river memory was shorter.
Should all be described in the reports. We didn't ever write this
up - except for the
these EA reports which are on the EA web site.
No idea how these have been applied in the two Authorities or by the EA.
Cheers
Phil
At 03:46 10/04/2008, Tom Wigley wrote:
>Phil,
>
>Can you send me any reports or papers on the latest
>long term riverflow reconstructions you've done.
>
>Has any of this been used in the context of future change?
>In other words, if one just added future projections
>to present (say the last 50 years), then the results
>would be different from the case if one added the future
>to a wider range of "present" based on observed variability
>over a number of centuries.
>
>More specifically, if the change in flow were a reduction
>of X units, and if there were a time a few hundred years
>ago when the natural flow was Y less than today, then
>a combination of an anthropogenic reduction of X and a
>natural reduction of Y would be doubly bad.
>
>So -- big question -- has the UK looked at the combined
>effect of X *and* Y?
>
>Thanks for your help,
>Tom.
Prof. Phil Jones
Climatic Research Unit Telephone +44 (0) 1603 592090
School of Environmental Sciences Fax +44 (0) 1603 507784
University of East Anglia
Norwich Email p.jonesatXYZxyz.ac.uk
NR4 7TJ
UK
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