Canadian Dam Association Bulletin - Winter 2018 - 13

with general middle and back loaded
accumulation patterns. These procedures are preferred because they capture
the spatial and temporal variability of
PMP rainfall as it would occur over the
complex terrain of the basin. Values
were derived for the all-season period,
extending from the middle of May
through the beginning of September.

2. PMP DEVELOPMENT
BACKGROUND
Definitions of PMP are found in most
of the Hydrometeorological Reports
(HMRs) issued by the National Weather
Service (NWS) and in the World
Meteorological Organization Manual for
PMP (WMO, 2009). The definition used
in the most recently published HMR
is "theoretically, the greatest depth
of precipitation for a given duration
that is physically possible over a given
storm area at a particular geographical
location at a certain time of the year."
(HMR 59, pg. 5, Corrigan, et al., 1999).
The Canadian Dam Association (CDA,
2007) defines PMP in a similar manner;
"the greatest depth of precipitation for
a given duration meteorologically possible for a given size storm area at a
particular location at a particular time
of the year, with no allowance made for
long-term climatic trends. The PMP is
an estimate of an upper physical bound
to the precipitation that the atmosphere
can produce."
Since the mid-1940s, several government agencies have been developing
methods to calculate PMP in various
regions of the United States. The NWS
(formerly the U.S. Weather Bureau) and
the Bureau of Reclamation have been
the primary agencies involved in this
activity. PMP values from their reports
are used to calculate the PMF, which,
in turn, is often used for the design
or safety evaluation of significant
hydraulic structures. Concurrently,
government and private consultants
have been deriving PMP values for various parts of Canada. There have been
several PMP studies conducted in the
region of western Alberta which are relevant to this study (e.g. Verschuren and
Wojtiw, 1980; Alberta Environment,
1985; Alberta Environment, 1988;
Alberta Environment, 1989; Northwest
Canadian Dam Association * Winter 2018

Figure 1: Locations of AWA PMP studies as of June 2016, Springbank is shown as number 83

Hydraulic Consultants, 1990). In addition, generalized PMP studies in the
contiguous United States relevant for
the location include HMRs (Tomlinson
and Kappel, 2009).
The Springbank basin is located
just north of the region covered by
HMR 55A. Although it provides generalized estimates of PMP values for a
large, climatologically and topographically diverse area, HMR 55A recognizes that studies addressing PMP
over specific regions can incorporate more site-specific considerations
and provide improved PMP estimates.
Additionally, by periodically updating
storm data and incorporating advances in meteorological concepts, PMP
estimates are improved significantly.
Previous site-specific and regional
PMP projects completed by AWA provide examples of PMP studies that
explicitly consider the topography of
the basins and characteristics of historic
extreme rainfall storms over climatologically similar regions (see Figure 1).
These PMP studies have received extensive review and the results have been
used in computing the PMF for the
watersheds and regions covered. This
study follows the same procedures
used in those studies to determine
PMP values for the Springbank basin.
This includes the use of the Orographic

Transposition Factor (OTF) procedure to
quantify the effect of terrain on the PMP
values and investigations of various spatial presentation of the PMP rainfall
that reflect the effect of the topography.
These procedures, together with Storm
Precipitation Analysis System (SPAS)
rainfall analyses are used to compute
PMP values using a .025°dd x .025°dd
grid for both in-place storm rainfall
analyses and PMP determination for
the basin. The grid based approach
provides improvements in the spatial
and temporal evaluation of the historic storm rainfall patterns and how
the PMP storm would occur over the
highly variable topography unique to
the basin.
2.1. Approach
The approach used in this study is
consistent with many of the procedures
that were used in the development of
the HMRs and as described in the WMO
documents, with updated procedures
implemented where appropriate. These
procedures were applied considering
the site-specific characteristics of the
basin and the unique effects of the topography both in the surrounding region
and in the basin. Terrain characteristics
are addressed as they specifically affect
rainfall patterns, both spatially and in
magnitude within the basin.
13



Table of Contents for the Digital Edition of Canadian Dam Association Bulletin - Winter 2018

BOARD OF DIRECTORS
PRESIDENT’S MESSAGE
UPDATING PMP FOR THE ELBOW RIVER: COMPLEX TERRAIN, UNIQUE SOLUTIONS
KELOWNA 2017
CDA AWARDS
ANNUAL GENERAL MEETING 2017
YOUNG PROFESSIONALS UPDATE
DAMS AND DIKES, WIKI STYLE
2017 FINANCE REPORT
CDA 2018 CONFERENCE: THE MANAGEMENT OF AGING DAMS
CDA NEWS BRIEF
BUYERS’ GUIDE AND TRADE LIST
Canadian Dam Association Bulletin - Winter 2018 - Intro
Canadian Dam Association Bulletin - Winter 2018 - cover1
Canadian Dam Association Bulletin - Winter 2018 - cover2
Canadian Dam Association Bulletin - Winter 2018 - 3
Canadian Dam Association Bulletin - Winter 2018 - 4
Canadian Dam Association Bulletin - Winter 2018 - 5
Canadian Dam Association Bulletin - Winter 2018 - 6
Canadian Dam Association Bulletin - Winter 2018 - BOARD OF DIRECTORS
Canadian Dam Association Bulletin - Winter 2018 - PRESIDENT’S MESSAGE
Canadian Dam Association Bulletin - Winter 2018 - 9
Canadian Dam Association Bulletin - Winter 2018 - UPDATING PMP FOR THE ELBOW RIVER: COMPLEX TERRAIN, UNIQUE SOLUTIONS
Canadian Dam Association Bulletin - Winter 2018 - 11
Canadian Dam Association Bulletin - Winter 2018 - 12
Canadian Dam Association Bulletin - Winter 2018 - 13
Canadian Dam Association Bulletin - Winter 2018 - 14
Canadian Dam Association Bulletin - Winter 2018 - 15
Canadian Dam Association Bulletin - Winter 2018 - 16
Canadian Dam Association Bulletin - Winter 2018 - 17
Canadian Dam Association Bulletin - Winter 2018 - 18
Canadian Dam Association Bulletin - Winter 2018 - 19
Canadian Dam Association Bulletin - Winter 2018 - 20
Canadian Dam Association Bulletin - Winter 2018 - 21
Canadian Dam Association Bulletin - Winter 2018 - 22
Canadian Dam Association Bulletin - Winter 2018 - 23
Canadian Dam Association Bulletin - Winter 2018 - 24
Canadian Dam Association Bulletin - Winter 2018 - 25
Canadian Dam Association Bulletin - Winter 2018 - KELOWNA 2017
Canadian Dam Association Bulletin - Winter 2018 - 27
Canadian Dam Association Bulletin - Winter 2018 - CDA AWARDS
Canadian Dam Association Bulletin - Winter 2018 - 29
Canadian Dam Association Bulletin - Winter 2018 - ANNUAL GENERAL MEETING 2017
Canadian Dam Association Bulletin - Winter 2018 - 31
Canadian Dam Association Bulletin - Winter 2018 - YOUNG PROFESSIONALS UPDATE
Canadian Dam Association Bulletin - Winter 2018 - 33
Canadian Dam Association Bulletin - Winter 2018 - DAMS AND DIKES, WIKI STYLE
Canadian Dam Association Bulletin - Winter 2018 - 35
Canadian Dam Association Bulletin - Winter 2018 - 2017 FINANCE REPORT
Canadian Dam Association Bulletin - Winter 2018 - 37
Canadian Dam Association Bulletin - Winter 2018 - 38
Canadian Dam Association Bulletin - Winter 2018 - 39
Canadian Dam Association Bulletin - Winter 2018 - CDA 2018 CONFERENCE: THE MANAGEMENT OF AGING DAMS
Canadian Dam Association Bulletin - Winter 2018 - 41
Canadian Dam Association Bulletin - Winter 2018 - CDA NEWS BRIEF
Canadian Dam Association Bulletin - Winter 2018 - 43
Canadian Dam Association Bulletin - Winter 2018 - 44
Canadian Dam Association Bulletin - Winter 2018 - BUYERS’ GUIDE AND TRADE LIST
Canadian Dam Association Bulletin - Winter 2018 - 46
Canadian Dam Association Bulletin - Winter 2018 - cover3
Canadian Dam Association Bulletin - Winter 2018 - cover4
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