Transcript The PFRA Watershed Project

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Gross and Effective Drainage Area
Delineation in the Prairie Provinces
Presentation at PPWB Prairie Hydrology Workshop
January 29, 2013
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Overview
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Concepts
Why is this of concern to the PPWB?
Background
Manual Process
Migration to GIS Environment
Recent Changes
What Does the Future Hold?
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Concepts
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Stichling and Blackwell (1957) presented a
paper proposing the concept of fluctuating
drainage area by year, by season, by event
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Godwin and Martin (1975) presented a paper
refining the concept of gross, effective and
dead drainage areas
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Gross Drainage Area
“The gross drainage area of a stream at a
specified location is that plane area,
enclosed by its drainage divide, which
might be expected to entirely contribute
runoff to that specified location under
extremely wet conditions. The gross
drainage boundary is the drainage divide
(i.e. the height of land between adjoining
watersheds).”
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Effective Drainage Area
“The effective drainage area is that
portion of a drainage basin which might
be expected to entirely contribute runoff
to the main stream during a flood with a
return period of two years. This area
excludes marsh and slough areas and
other natural storage areas which would
prevent runoff from reaching the main
stream in a year of ‘average runoff’.”
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Dead Drainage Area
“Drainage is considered dead if there is no
outflow from an area even under very
wet conditions. This situation is
common on the Canadian Prairies where
major depressions having sloughs and
shallow lakes with no outlets are usually
associated with dead drainage. A dead
drainage basin includes all of the area
tributary to such a depression.”
Why is this of concern to the PPWB?
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Need drainage areas that are acceptable to all
member agencies
For purposes of apportionable flow
determination, only projects within the
effective drainage area are considered as
depletions to the natural flow
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Background
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1970 - PFRA, as part of an IHD Study, undertook
task of delineating drainage areas (543 stations)
Early 1970s - Need for standardization
1975 - at PPWB’s request, PFRA accepted
responsibility for delineating areas on streams;
covered by Master Agreement on Apportionment;
commitment reaffirmed in June 2003
1978 - Hydrology Memorandum #25 (1191 stations)
and 3 subsequent addendums
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1983 - Hydrology Report #104 (1687 stations)
with 8 subsequent addendums (Addendum #8
published in 2001 included 2689 stations)
1994 - Decision made to migrate data base and
process to a GIS environment
Late 1990s - digitizing lines and developing a
GIS process
2001 - Completed migration from manual to
GIS environment
2008 - Current GIS version (8) includes entire
Prairie Provinces area (3312 stations)
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Manual Process
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Time consuming and resource intensive
Difficult to update data base
Limited product usability
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Index Cards
and Summary Reports
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Migration to GIS Environment
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Process
- digitize delineated boundaries
- develop gross & effective polygons
- develop linkage network
- compare manual & GIS tabulations
to check/confirm linkages
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Migration to GIS Environment
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Benefits
- data base easy to update/maintain
- quick automated revision of areas
- easy access of data base by users
- unlimited application potential
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Recent Changes
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Association of all dead drainage areas
with a drainage basin
Addition of “artificial” stations to give
complete coverage of Prairies
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Ongoing Enhancements
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Continue to refine delineations
- use 1:20,000 scale coverage where available
- check delineations using digital NTS maps
(DEMs)
Incorporate local information provided by users
Current (Version 8, 2008) Product
http://www.agr.gc.ca/nlwissnite/index_e.cfm?s1=data_donnees&s2=details
&s3=lc-ct&page=wb-bv_plus
What Does the Future Hold?
?????? – PFRA no longer exists, and there is no mandate
in the current organization to continue drainage area
delineation activities
International Harmonization of Watershed Boundaries and
Hydrographic Features (IJC)
Development of Watershed Delineation Tool – for
specific projects, not for drainage area database
maintenance
Features of the Watershed Delineation Tool
http://www.agr.gc.ca/watersheddelineation
Delineate watershed boundaries anywhere within the
Canadian Prairies
Produce maps and hydrology reports containing standard
watershed information
Delineated watershed boundary and area
Contributing and non-contributing areas
Longest flow path, stream length and slope, draiange density
Location of WSC gauging stations
Download watershed boundaries to standard geographic
formats (KML or shape file)
Easy to use and interactive
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QUESTIONS???