Quantifying fragmentation
of freshwater systems using
a measure of discharge
modification (and other
applications)
David Theobald, John Norman,
David Merritt (USFS)
Natural Resource Ecology Lab, Dept of Recreation
& Tourism, Colorado State University
Fort Collins, CO 80523 USA
26 July 2005
Freshwater fragmentation
Southern Rockies Ecosystem Project.
2000.
Fragmentation and flow modification
Deynesius and Nilsson (1994) –
77% of upper 1/3 of northern
hemisphere rivers are strongly
or moderately affected
- F = regulated/total channel length
- R = % of VMAD (cumulative
reservoir live, gross capacity)
Regulated
Channel
Length
(RCL)
Total
Channel
Length
(TCL)
Network-based
flow
modification
Degree of modification (F) is ratio of unmodified discharge as a proportion
of total annual discharge
F = ( Q-S ) / Q
- Q is cumulative annual discharge
- S is cumulative dam “normal” storage
Predicted discharge
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Average annual precipitation &
temperature, basin area
Vogel et al. 1999
Vogel
Discharge map of US
National Inventory of Dams


~80,000; >4 m height
Map of dams
Thanks!

Comments? Questions?

Funding/Disclaimer: The work reported here was
developed under the STAR Research Assistance
Agreement CR-829095 awarded by the U.S.
Environmental Protection Agency (EPA) to
Colorado State University. This presentation has not
been formally reviewed by EPA. The views
expressed here are solely those of the presenter and
STARMAP, the Program (s)he represents. EPA does
not endorse any products or commercial services
mentioned in this presentation.


FLoWS:
www.nrel.colostate.edu/projects/
starmap
davet@nrel.colostate.edu
CR - 829095