KNOW THE FLOW WHEN YOU GO

The evolution of the internet provides great information for paddlers. As well as surfing standing waves in our favorite rapids, we can now surf websites to investigate new boats and gear, different rivers and what’s up in the paddling scene. Perhaps the most useful new web resource is ‘real-time’ stream flow data. Around 1995, Alberta Environment (AE) introduced the ‘Flow Phone’, a digital dial-up where we could phone a toll-free number for flow information for selected river reaches. A couple of years ago, AE introduced an internet site that provided these data. With the new millenium, AE has upgraded their website to include ‘Near Real-Time Hydrometeorological Data’? It’s great. This new system has far more streams and gauging sites and provides hourly or half-hourly data for the past few days up to about six hours prior to your internet visit. We can now find out more current flow conditions and also determine the recent pattern. Is the river rising or falling and is it likely to be suitable for a Saturday splash? We can also access the data after a trip and keep track of the flow that provides ideal conditions in our favorite rapids or play-spots. In the style of Goldilocks we can find out what’s too low, what’s too high and what’s just right.
The Alberta flow data can be accessed through the ‘Near Real-Time Hydrometeorological Data’ of Alberta Environment’s website
http://www.gov.ab.ca/env/water/. Or you can go directly to those data through
http://www.gov.ab.ca/env/water/Hydrometeorological/Index.html

If you are going to the Kananaskis, you can access Trans Alta Utilities' website at http://www.transalta.com/Website/river.nsf. The American agency, U.S. Geological Survey, keeps track of their stream flow data and has had a friendly and comprehensive real time hydrometric site for a number of years. It can be reached at http://water.usgs.gov/realtime.html. Before you head south to Montana, Idaho, or points beyond, a stop at the USGS site can reveal what’s going on with the American rivers.
We’ve found it a bit harder to find flows for British Columbia rivers but there are some websites including B.C. Hydro’s site at http://eww.bchydro.bc.ca/powersupply/reservoir_hydromet/hydromet/colum.html.
and Environment Canada's http://www.weatheroffice.com/water/Map.asp.

HOW ARE STREAM FLOWS MEASURED?

Well, if anybody cares, they’re not. The actual measurement is of ‘stage’, or river height. A gauging station is typically located in an accessible location like a bridge and it usually consists of a metal culvert that is vertically buried near the stream edge. There’s a small shack on top of the culvert and this contains an instrument that measures the water surface in a well created by the culvert. That instrument often consists of a float assembly that rises and falls with the rise and fall of the river since there’s a pipe linking the culvert well to the stream. The gauging station shack also typically has some exterior features including an antenna to transmit the data to a Provincial database center and often a solar cell to power the unit. These gauging stations are often situated at our put-in or take-out bridges and once you start noticing them, you’ll find they’re very common in southern Alberta. After stage is measured, the data are converted to ‘discharge’, or rate of flow, using a ‘ratings’ or ‘stage-discharge’ curve. At different flows, someone will visit the gauging site with a device that measures stream velocity. That instrument looks like a small torpedo or metal fish with a propeller and is very heavy to permit its systematic suspension at different positions across the river. Thus, someone works across a bridge (or uses a cable car. This is why they’re common across our rivers) measuring water depths and velocities. These values are then accumulated across the river to calculate the overall flow. These calibrations are conducted at various flows and are plotted to produce the ratings curve that relates river flow to river height. The river height that is continuously measured in the gauging shack is thus converted to flow, which is reported.


A typical gauging station. This one is on the Elk river near the town of Fernie, BC.

The inside of the gauging station. Note the paper copy as well as the electronic recorder on the right.

A typical torpedo used to determine river velocity

In the last 20 years there have been many people, and many approaches that have contributed in the determination of what makes a good river level. Some of these methods include:

Professional Judgement, a single visit

Professional Judgement, multiple visits

Surveys of paddlers and paddling goups an clubs

Present Flow Surveys - take out interviews

Multiple Flow Comparison - Users who have used the site at different times

Controlled Flow Study - Deliberate flow regulation and assessment

Consistent proportions of mean annual flow

Single Transect Method - depth criteria at shallowest point and determine discharge

The LOW (minimum flow discharge that will still provide a reasonable quality paddling experience - a flow tht paddlers would return to) and IDEAL the lower end of the "ideal" flow range) flows on this website are based on an average of profesional Judgement, Multiple Flow Comparisons, surveys of over 4000 paddlers from the last 20 years, and a Depth Discharge Method (low (Minimal) means 0.6 cm and ideal (Sufficient) means 0.75cm).