River Statistics

    The Oldman River is about  330 km in length and drains an area (drainage area) of about 17, 700 km2. To fully understand the importance of this river to Southern Alberta, one must note the basic hydrological statistics of this river. The statistics used in this web page are from 1990, and are taken from the Inland Water Directory of Environment Canada. Some river statistics are dependent on time and region, and thus this portion of the website will fully explore the implication of time and space on such statistics.

Mean Monthly Discharge- The volume of flow per unit area of time (seconds) through a given cross section, is the product of average velocity and crossectional area.

Q = discharge
w = width
d = depth
v = velocity

It is usually calculated with  Q = wdv (Easterbrook, 1993)

I have used Environment Canada data from four sources- the Three Rivers Gap (which has limited data), Brocket, Lethbridge, and near the mouth of the South Saskatchewan River.

Area 1: Three Rivers Gap. Mean discharge data computed from 1944-1989 (Some months unavailable)
 
Month Average Discharge (M3)
May 42.1
June 45.1
July 12.5
August 6.89
September 6.10
October 5.89

Area 2: Brocket, Alberta.  Mean discharge data computed from the years 1966-1990
 
 
Month Average Discharge (M3)
January 7.75
February 8.71
March 13.0
April 33.2
May 128
June 136
July 49.3
August 23.4
September 16.1
October 15.2
November 12.7
December 9.31
YEARLY MEAN 37.7

Maximum Daily Discharge for the year 1990:   418m3,    on May 26
Minimum Daily Discharge for the year 19904.08 m3  on December 23
 
 

Area 3: Lethbridge. Mean discharge data computed from the years 1910-1990.
 
Month  Average Discharge (M3)
January 21.6
February 23.5
March 40.9
April 78.8
May 235
June 320
July 117
August 39.1
September 37.4
October 41.6
November 37.3
December 23.7
YEARLY MEAN 83.7

Maximum Daily Discharge for the year 1990:   685m3,    on May 31
Minimum Daily Discharge for the year 1990:   7.23m3,   on December 28
 

Area 4: Near Mouth.  Mean data computed from the years 1964-1990
 
 

Month Average Discharge (M3)
January 18.3
February 24.0
March 38.2
April 58.4
May 156
June 272
July 88.0
August 30.3
September 37.7
October 42.9
November 42.2
December 23.3
YEARLY MEAN 67.7

Maximum Daily Discharge for the year 1990:   690m3,    on May 28
Minimum Daily Discharge for the year 1990:   8.08m3,   on September 28

Conclusions: As the above chart, and information shows, discharge- the amount of water flowing through the Oldman River, seems to have its peak flow in June, and has its ebb flow during December. It should also be noted for this data, that velocities are estimated, not measured (Environment Alberta) because of the the many variables which affect river velocity. These might include: channel depth, cross sectional area, and other factors, such as coefficient of friction and slope which widely influence river velocity over small areas.



Sediment Load- Streams continually wear down and the land and transport an transport immense amount of rock debris to the oceans annually. Fine graded, small particles, such as clay, silts and sands are constantly in suspension in river water. This measurement is referred to as sediment load and is measured as tonnes per day.  Measurements in winter months are not made by Environment Canada, because ice conditions yield unreliable data, and there is relatively no sediments in suspension.

I have chosen three tests sites to show rate of change (monthly change) of sediment load over the Oldman River. These sites include Brocket, Lethbridge, and near the mouth of the South Saskatchewan River.

Area 2: Brocket, Alberta:
Month Sediment Load (Tonnes/day)
March 55
April 228
May 1329
June 298
July 141
August 45
September 102
October 318
Maximum Daily Sediment Load for the year 1990:   on May 26

Area 2: Lethbridge, Alberta:
Month Sediment Load (Tonnes Day)
March 198
April 447
May 4928
June 2812
July 162
August 48
September 251
October 131
Maximum Daily Sediment Load for the year 1990:   on May 28

Area 3: Near Mouth of Oldman River
Month Sediment Load (Tonnes Day)
March  2
April 14
May 511
June 85
July 7
August 3
September 3
October 1
Maximum Daily Sediment Load for the year 1990:   on May 28
 

Conclusion:

Have a close look at peak discharge and peak sediment load. For this region, the peak sediment load occurs a whole month before before peak discharge. Does this perplex you? It shouldn't. Peak sediment load will occur before peak discharge- why? Well, as the early melt waters come into the Oldman River, in the early spring, around May, all the sediments deposited in the summer and fall of the previous year are easily picked up and put into suspension, well before peak discharge happens in June.