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Q.
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Who contributes to Alberta River Basins Web/site?
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A.
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There are several groups that contribute to different parts of Alberta'
s River Basins section:
- Flow Forecasting team of Environmental Monitoring and Evaluation Branch - Responsible for:
- Basin maps and graph plots of near real-time hydrometeorological data
- Advisories and Warnings
- Forecaster's Comments
- Water Supply Outlook
- Precipitation Maps and Data Summaries
- Frequently Asked Questions
- Wabamun Lake Report.
- Data Management of the Environmental Monitoring and Evaluation Branch - Responsible for the
operation in both the assembly and processing of near real-time data and the posting of this hourly data
in tabular format to the Web/site.
- Regional Services - Responsible for portions of the Web/site that are regional
in nature such as:
- Water Operations Reports
- Water Management Plans
- Operational Flow Data
- Operational Flow Forecasts
- Licence and Monitoring Flows
- Water Act Notices
- Highwood River Weekly Streamflow Report
- Regional reports such as the Environmental Assessment Committee's
recommendations for the management of water and the environmental mitigation program
associated with the Oldman Dam.
- Webmaster - Responsible for overall technical aspects of the Web/site.
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Q.
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Who can I contact if my question is not on the FAQs?
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A.
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Contacts are:
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 Back to top
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Q.
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What are the functions of the Flow Forecasting Team?
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A.
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Flow Forecasting's primary functions are:
- Forecast floods and high flows in rivers and streams:
- Issue advisories and warnings
- High Streamflow Advisories
- Flood Watches
- Flood Warnings
- Assist Regional Services in issuing advisories related to ice and ice jams.
- Forecast water supply
- Support Water Management by providing information as required for:
- Determining Instream flow needs
- i.e. fish, water intakes, ferry crossings etc.
- Tracking Apportionment (sharing) compliance
- 1909 Boundary Water Treaty with U.S.
- 1969 Master Agreement on Apportionment with Prairie Provinces
- Water Mastering
- Managing Water Quality
- Support management of Alberta's water management infrastructure by:
- Developing flood operating procedures for provincially owned dams
and provide operational advice to dam operators
- Providing forecasts of;
- Floods
- Water quality
- Water Supply
- Inflows
- Natural flows
- Report current conditions for:
- Stream levels and flows
- Lake and reservoir levels
- Precipitation
- Snowpack
- Temperature, wind, humidity and other miscellaneous meteorological parameters.
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Definitions/Terminology
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Q.
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What is a drainage basin?
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A.
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A drainage basin, also often referred to as a catchment area or
watershed, is the surface area which drains to a lake or contributes to the flow
at a particular point in a stream or river.
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Q.
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What are quartiles and how are they related to flows, water storage and snow
water equivalent?
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A.
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Quartiles are three values which divide sorted data
sets into four (approximately) equal parts. The lower quartile
(1st quartile) is the value that separates the bottom ¼ of a dataset
from the remaining top ¾ of the dataset. The second quartile (median) is
that value that divides the dataset into two equal parts such that
50% of the values are lower and 50% of the values are higher than the median
(2nd quartile). The upper quartile (3rd quartile) is that value that separates the upper ¼
of a dataset from the bottom ¾ of a dataset.
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Quartiles are used to show the "normal range" of data (band between the lower
and upper quartiles) for flows, water storage and snow water equivalent (pillow data).
See also Water Supply Outlook and how normal
is applied in the Water Supply Outlook.
Note that the median for our flow and pillow datasets is termed the average. The median
and average for most of our datasets are very close given the large numbers of data points
within our datasets.
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Q.
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What is snow water equivalent? How is this different from snow depth?
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A.
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Snow depth is the measurement from the top of the snow to ground level.
The amount of water produced by a snowpack of a given depth varies depending
on the density (water content) of the snowpack. Snow water equivalent is the
amount of water that would be obtained by melting a depth of snow.
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Q.
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What is a snow pillow?
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A.
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A
snow pillow is an a automated set of apparatus that measures, records and transmits snow water equivalent.
from a remote site to an office or laboratory equipped to receive such information.
Precipitation and temperature gauges are usually part of the total installation.
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Q.
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What is a snow course?
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A.
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A snow course is a series of approximately 10 snow sampled points spaced at approximately 30 metre intervals. At
each sample point the snow water equivalent is determined manually on site. All manually determined
snow water equivalents from each sample point are then averaged to arrive at one snow water equivalent value
for the whole snow course.
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Q.
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What is the difference between snow pillow and snow course data?
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A.
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Snow water equivalent values on the snow pillow may or may not match the snow course
value at a particular location. While snow pillow data is very valuable information,
the quantity of snow on the pillow is only representative of the accumulation at that
specific spot. A snow course survey is measured at numerous spots and provides a more
representative value of snow in the area. In some locations, there can be considerable
difference between the snow pillow and snow course values. Factors such as wind and
exposure of the site can cause the snow pillow values to be significantly different from
the snow course survey. The snow pillow graphs on our Web/site show the daily average
snow water equivalent. The monthly snow survey is the average of all measurements conducted
within five days of the end of the month. Also, where snow pillow and snow course measurements
are available for the same site, snow pillow records tend to be much shorter (10-15 years) in
length compared to the snow course sites. As a result, the difference in the average
value between the snow pillow and the snow course can be attributed to snow water equivalent
being derived two different ways (physically measured compared to an instrument reading),
site location and length of data record. In some cases, the values can deviate by 10-20%.
Therefore, while snow pillows are excellent for analyzing trends and for monitoring accumulation
between snow surveys, snow course values should always be used when considering the quantity of
snow at a particular location as they best represent that area.
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Q.
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What is meant by water year?
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A.
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Water year is the time period from November 1 of one year through October 31
of the following year. The water year number comes from the calendar year for the January 1
to October 31 period. For example, Water Year 2000 would begin on
November 1, 1999 and continue through to October 31, 2000.
The water year instead of the calendar year is used in the Water Supply Outlook since Alberta's
hydrologic cycle essentially begins November 1 with winter snow accumulation and
precipitation followed by spring runoff which replenishes the water supply.
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Q.
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What is meant by Water Mastering?
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A.
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Water Mastering is the monitoring and enforcement of the Water Act's "first in time, first in right"
priority allocation system undertaken by Regional staff (most notably staff responsible for
water management in the southern region) to limit water withdrawals when diversions exceed the
water supply during low water periods. Depending on the availability of water,
water licencees with low (most recent) priority numbers (date at which a water
licence is issued) are requested to either limit their water withdrawals to a certain
fraction of their licenced allocation or refrain from withdrawals of any amount.
Regional staff base their water allocation decisions on information such as the Monthly
Water Supply Report, natural flow reports, current flow information, etc.
Water management orders may be issued to selected licencees and withdrawals are monitored
by the Water Master.
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Q.
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What is meant by near real-time data?
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A.
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Near real-time data is data that is available for viewing after a relatively short time span between
the time of data sampling from a remote location and the viewing of that same data within the comfort
of an office or laboratory. The remote location may be as far away as a distant mountain location or
as close as a point on a river in the city where the viewing facilities are located. Alberta Environment
personnel view the majority of near real-time data within as little as 1 hour from the time of sampling.
Public viewing of the same data presented in graphical and table format on the Web/site is later and largely
dependent on frequency of updates to the Web/site.
Alberta Environment's near real-time data gathering process takes advantange of recent advances in satellite,
telephone and computer communication technology.
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Q.
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Is the near real-time data checked?
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A.
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The near real-time hydrometeorological data is quality assessed and quality controlled (QA/QC'd)
daily in the morning to ensure accuracy and completeness. During flood events
hydrometeorological data are "QA/QC'd" more frequently.
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Q.
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Why has today's flow value changed from yesterday's value?
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A.
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Water levels and flow values are adjusted as required to compensate for
either natural river environment changes (vertical or horizontal channel shifts,
beaver dams, aquatic vegetation, etc.) or instrumentation errors (staff gauge movement,
instrumentation drift, power fluctuations etc.).
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Q.
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When are the near real-time data and associated figures updated on the Internet?
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A.
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Update frequencies are generally as follows:
- River data figures are updated four times daily
- Precipitation data figures are updated four times daily
- Lake and Reservoir level figures are updated four times daily
- Snow data figures are updated twice daily
- All data tables are updated on an hourly basis however due to transmission
times or failed connections the data will be older than the time of update.
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Q.
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How are stream levels/stages acquired?
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A.
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Stream levels/stages are acquired at a specific location for a stream or river by referencing
the water level to a known vertical point (elevation). That vertical point may be some structural
element on a structure on/by the river, a spike in a tree, a Geological Survey of Canada (GSC) survey benchmark, etc.
The reference point may be an assumed elevation or a known geodetic elevation (reference to sea-level), however
what is important is that all subsequent water levels be referenced to that initial elevation in order
to have a continuous record of water levels. For ease in determining that distance between subsequent
water levels and that initial elevation, a gauge (can be as simple as a long ruler) is placed in a strategic location so that: water levels
contact the gauge over a wide vertical range of water levels, and, those levels can be easily determined either
by manual observance or automation. A point on the gauge is referenced to the initial elevation to establish the elevational relationship
between the gauge and that initial elevation. For a more detailed description of gauges and recording methods we
refer you to Water Survey of Canada's gauging stations section of their
Hydrometric Technician Career Development Program.
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Q.
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How do you get flows(discharges) from stream levels?
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A.
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By measuring flow (a costly and time consuming task) for a range of water stages, a stage-discharge relationship
is established for a specific location on a stream or river. When the stage-discharge
relationship is fully established a corresponding flow/discharge can be derived from a given water level (stage).
Water levels can be acquired quickly and remotely therefore providing near real-time flows.
Water Survey Canada has an excellent Web/site that describes in detail
the relationship between stage and discharge
See also the next FAQ for flows under ice conditions.
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Q.
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Why are flows not updated during the winter months?
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A.
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All real-time hydrometric flows are derived by measuring the water level/stage, and
applying that level to a relationship which relates stage to flow. Since ice cover
introduces a number of uncertainties, such as additional friction losses and back water
effects, the stage versus flow relationship, and, consequently the flow estimate is not
reliable under ice conditions.
However some flows can be estimated using deterministic and/or statistical methods such
as the
Athabasca River below Fort McMurray. The Athabasca River below Fort McMurray is the
only winter flow estimate available online as of November 2002.
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Q.
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Is there any real-time Water Quality and Private Reservoir data available?
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A.
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Near real-time Water Quality data (water temperature, dissolved oxygen, water pH, etc.),
and Private Reservoir hydrometeorological data (reservoir water level, outflows,
air temperature, etc.) can be viewed under the category "Miscellaneous and Water Quality Data".
Willow Creek
at Oxly Ranch is a good example of water quality data.
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Q.
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Why are there two categories of meteorological data, i.e. "precipitation" and "meteorological"?
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A.
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The "precipitation" category contains the three and six hour accumulated
totals which in many cases is graphed. The "meteorological" data
(table format only) contains not only hourly accumulated
precipitation but other meteorological parameters such as air temperature,
humidity, wind direction, wind speed, etc.
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Q.
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Where can I get historical data since the data only goes back two or three days?
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A.
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There are two sources of historical data related to the near-real-time data:
- For Alberta Environment historical hydrometeorological data contact
Data Management of the Environmental
Monitoring and Evaluation Branch.
- For national historical hydrometeorlogical data visit Environment Canada's
self-serve Web/site
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Q.
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Is near real-time hydrological data for Alberta available elsewhere on the Internet?
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A.
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Yes, Water Survey of Canada provides
near real-time water levels
from 1200 stations across Canada including alberta.
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Q.
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How do I interpret a streamflow graph?
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A.
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Here's how to
interpret a stream flow graph.....
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Q.
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How do I interpret a precipitation graph?
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A.
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Here's how to
interpret a precipitation graph...
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Q.
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How do I interpret a snow pillow graph?
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A.
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Here's how to
interpret a snow pillow graph...
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Back to top
Advisories and Warnings
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Q.
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What causes flooding in Alberta?
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A.
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There are three causes of flooding in Alberta
- Snowmelt for plains and mountains: Snow on the plains usually melts and runs off during
the March to April period. Excessive, rapid melting may flood smaller streams and rivers
having their headwaters in the plains areas. Mountain snowmelt usually occurs
during the May to July period. While mountain snowmelt may result in localized flooding, snowmelt
by itself is generally not sufficient to cause flooding in major mountain fed streams unless
accompanied by rainfall.
- Rainfall: Rainfall affects big and small watercourses in Alberta.
Flooding along major mountain-fed rivers (such as the Oldman and Bow Rivers)
is caused by heavy rainfall, or heavy rainfall during mountain snowmelt.
- Ice Jams: Ice Jams can occur anytime during the winter, although freeze-up or break-up are the
most usual times. They can be initiated when the ice cover breaks up into floes and moves
downstream. A jam occurs when the ice floes accumulate at a location and partially or completely
block the channel. The ice blockage restricts the flow in the river, causing water levels to increase.
In some cases the water levels can increase enough to cause flooding along the jam. Ice jams tend to
form repeatedly at certain locations.
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Q.
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What does the phrase "advisories and warnings" mean?
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A.
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The phrase "advisories and warnings" refers to the types of notices
that advise, watch for, or warn of future (hours to days) abnormally high water levels.
The following advisories and warnings issued by the
Flow Forecasting Team are ranked from lowest to highest in terms of risk to life and severity
of property damage:
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The following advisories are issued by
River Engineering and Water Monitoring of Regional Services Northern Region when streams and
rivers are ice covered:
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Advisories only are issued during ice conditions due to the
unpredictability of
water levels when streams and rivers are ice covered.
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Q.
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What does a Spring Runoff Advisory mean?
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A.
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A Spring Runoff Advisory means that stream levels are rising or expected to rise due to snowmelt
and no major flooding is expected. Minor flooding in low-lying areas is possible. Anyone
situated close to the streams affected (property owners and the general public) is advised
to be cautious of rising levels.
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Q.
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What does a High Streamflow Advisory mean?
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A.
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A High Streamflow Advisory means that stream levels are rising or expected to rise rapidly and no major
flooding is expected. Minor flooding in low-lying areas is possible. Anyone situated close
to the streams affected (campers, fishermen, boaters and the general public) is advised to
be cautious of the rising levels.
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Q.
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What does a Flood Watch mean?
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A.
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A Flood Watch means that stream levels are rising and will approach or may exceed bankfull.
Flooding of areas adjacent to these streams may occur. Anyone situated close to the
streams is advised to take appropriate precautionary measures.
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Q.
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What does a Flood Warning mean?
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A.
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A Flood Warning means that rising river levels will result in flooding of areas adjacent
to the streams affected. Anyone situated close to the river should take appropriate
measures to avoid flood damage.
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Q.
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What does an Ice Jam Advisory mean?
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A.
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An Ice Jam Advisory means that ice jams have been reported in a river or stream.
The potential exists for sudden increases in river levels both upstream and downstream
of the ice jam. Changes in water levels can occur upstream of the jam as water collects
behind the jam. If the jam releases suddenly, a surge of water could be sent downstream.
Local authorities and residents are advised to monitor the ice covers and water levels in the rivers
in their communities particularly in areas where ice jams have been a problem in the past.
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Q.
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What is the significance of a River Breakup Advisory?
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A.
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A River Breakup Advisory is usually issued with the onset of warmer Spring temperatures
and implies that ice breakup may result in the formation of
ice jams. The location and occurrence of ice jams, and possible associated
flooding, are very unpredictable. Local authorities and residents are advised to monitor the
ice covers and water levels in the rivers in their communities particularly in areas where
spring ice jams have been a problem in the past.
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Forecaster's Comments
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Q.
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What is Forecaster's Comments?
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A.
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Forecaster's Comments summarize weather and stream conditions for relatively short
term periods and provide additional information on current issues affecting streams
in the province. During high water/flood situations, the Forecaster's Comments
are very important for learning more about an event.
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Back to top
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Q.
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When are Forecaster's Comments updated?
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A.
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During "normal" weather and stream conditions the Forecaster's Comments are usually updated
every two to five days. However during a high water, flooding, or ice jam event, the Forecaster's Comments are
updated as often as needed - perhaps numerous times during a 24 hour period.
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Water Supply Outlook
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Q.
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What is the Water Supply Outlook?
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A.
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The Water Supply Outlook is a current conditions report that contains a summary of current snowpack, precipitation,
river flows, reservoir storage and soil moisture and their impacts on potential runoff in
two areas, the plains and the mountains. Plains area runoff is important for replenishing
soil moisture and water storage in local storage facilities, such as dugouts. Runoff from
the mountains is important for the major rivers in the province where reservoirs store
water supplies for irrigation, hydroelectricity and community & municipal purposes.
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Q.
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When is the Water Supply Outlook issued?
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A.
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The report is usually issued within the first 10 days of the month after:
- all data values are compiled and analyzed from the previous
month,
- additional information from second party datasets are received by the Flow Forecasting group
-some information/datasets are not received until well into the second
week of the month.
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Q.
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How are water supply forecasts produced? Why do forecasts change from
month to month, sometimes dramatically?
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A.
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Forecasts are produced by assuming normal weather (precipitation, temperature) in the
future. Forecast runoff is modelled using the current antecedent conditions and
future scenarios. The further the departure from normal weather, the larger the change.
Monthly updates usually result in more accurate forecasts as the year progresses since the period
of known data increases and the period of unknown (forecasted) data decreases.
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In dealing with future scenarios, assumptions are made to how/when weather patterns occur.
If the weather does not follow its "normal" pattern, forecasts can change dramatically.
For example, a major storm will create much greater runoff than normal.
Similarily, a major hot spell will create much-above-average runoff from snowmelt.
The forecast based on normal weather weather is the probable forecast. Other
forecasts are produced using lower quartile, upper quartile, and lower decile (10% chance
of precipitation, being lower) precipitation. These forecasts provide a reasonable
range of (lower to upper quartile) volume and a reasonable minimum (lower decile).
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Q.
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What information can I expect within the monthly Water Supply Outlooks?
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A.
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Beginning with the first two months of the water year,
information that you would likely find within the Water Supply Outlook from month to month is:
- The November and December Outlooks
both feature data and assessments on province-wide precipitation for previous months
and reservoir storage status.
- The January report provides comments on the previous month's precipitation
and reservoir status but also reports and comments on the previous fall
(September-October), and winter precipitation to date (November and
December). This is the first report of the water year to report and
comment on the status of snow conditions (such as snow water
equivalent in the mountains), and provides a water supply forecast for the
most southerly drainage basin, the Milk River Basin.
- The February to September Water Supply Outlooks:
- report and comment on:
- the fall, winter and summer precipitation that
accumulates for each successive month
- snow accumulations as reported from snow pillow and snow course
measurementsfor both the mountain and plains areas
(Snowpack conditions are usually not a significant
factor after the mountain runoff is substantially completed usually around the end of June)
- reservoir storages
- forecast mountain runoff volumes for the March to September
period for the major basins, and,
- forecast spring plains
runoff, or describes the spring runoff as it is occurring. Plains
spring runoff is usually complete by the end of April.
- The October Water Supply Outlook is unique in that it is not only the last Outlook in the water year
reporting September's precipitation and reservoir status, but also reviews recorded and forecasted
water supplies in the province for the water year.
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Q.
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If I know what the snowpack conditions are like, why do I need streamflow forecasts
to evaluate my future water supplies?
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A.
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Although snow water content is a major contributing factor to the runoff forecast,
other components such as rainfall and soil moisture conditions affect the amount
of spring and summer streamflows. Streamflow forecasts, which consider snowpack
plus other factors related to runoff, provide a better overall picture of streamflow
conditions than just using snowpack. This is true whether the user wants specific flow
values or an indication of general conditions.
(United States Dep't Agriculture, National Water and Climate Center, Publications)
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Q.
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What is meant by normal precipitation?
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A.
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Normal precipitation for a specific location is determined by computing
the average precipitation for a specific time period over the last 30 years.
Typically most normals are based on the 1971-2000 data. The
percent of normal precipitation is equal to: (the present precipitation total/
normal precipitation) x 100.
For most sites the following percentage ranges
are used for precipitation:
- much-above-normal : values 130% and greater
- above-normal : values between 110% and 130%
- normal : values 90% to 110%
- below-normal : values between 70% and 90%
- much-below-normal : values 70% and below
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Back to top
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Q.
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How is normal defined for runoff and snowpack conditions?
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A.
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Runoff and snowpack are compared to the average of the entire dataset. The following
ranges are used for comparing runoff and snowpack to historical values:
- much-above-average : ranked in the upper 15% of historically recorded values
- above-average : ranked between the upper 15% and 35% of historically recorded values
- average : ranked between the upper 35% and lower 35% of historically recorded values
- below-average : ranked between the lower 15% and 35% of historically recorded values
- much-below-average: ranked in the lower 15% of historically recorded values.
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Q.
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How is normal water storage defined?
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A.
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Normal water storage is based on the quartile system using
historically recorded values for the given time period.
Storage values that fall between the upper and lower quartiles of historically recorded levels
for the perod are considered normal.
Storage values that fall below the lower quartile are considered below-normal, similarily
storage values that are above the upper quartile are considered above-normal.
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Q.
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What is the difference between natural (adjusted) flows and observed flows?
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A.
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"Observed flows are the flows measured at a given point on a stream, regardless of the
effect of upstream water management on streamflows. Natural flows are the
flows that would have occurred without human influence. Natural
(adjusted) flow is calculated by adjusting observed flows for changes in storage and
gauged diversions that affect streamflow.
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Map and Data Summaries
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Q.
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When are the precipitation maps updated?
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A.
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Daily and weekly precipitation maps are usually updated before noon Monday to Friday.
Monthly precipitation is usually before noon every Monday.
Storm Event maps may be updated at any time during a significant precipitation event.
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Q.
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What is meant by "accumulated" precipitation?
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A.
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Accumulated precipitation is the total amount of precipitation
that falls within any given time period at a specific location.
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Q.
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When during the day is the Provincial Air Temperature Summary updated?
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A.
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The Provincial Air Temperature Summary is updated twice daily at approximately 9:00 AM.
and 5 p.m.
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Q.
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When during the day is the Provincial Reservoir Storage Summary updated?
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A.
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The Provincial Reservoir Storage Summary is usually updated daily before noon Monday to Friday.
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Related Web sites
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Q.
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Can you direct me to other other related Web sites?
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A.
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Please find below related links:
- Provincial;
- National;
- International;
- Canoeing;
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