date: Thu, 10 Apr 2008 06:52:00 -0600
from: "Joel Smith" <JSmith@stratusconsulting.com>
subject: RE: longterm river flow (2)
to: "Phil Jones" <p.jones@uea.ac.uk>, "Tom Wigley" <wigley@ucar.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
   jsmith@stratusconsulting.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.jones@uea.ac.uk
   NR4 7TJ
   UK
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