PROVINCIAL LOW WATER LEVELS CONDITIONS REPORT

Update for September 1-21 2003

Region

Precipitation (monthly) 1

Flows (monthly)2

MNR Southcentral
  • To date (Sept 25, 2003), watersheds in 12 Conservation Authorities (CA) are in a confirmed Low Water condition – 10 CA’s have watersheds in Level I3 only: (Kettle Creek, Quinte, Ausable Bayfield, Kawartha Region, Lower Thames Valley, Nottawasaga Valley, Upper Thames Region, Long Point Region, Hamilton Region, Otonabee Region); and 2 CAs have watersheds in Level II: (Catfish Creek, Grand River)
  • Precipitation amounts have improved since the last Conditions Report was issued. However, all but 4 stations reported precipitation below 70% of the average precipitation by the third week of September1(By the end of the third week, 70% of the average precipitation for August would indicate a trend toward the average for the month). Precipitation amounts expected to accompany Hurricane Isabel were much less then initially forecast. With the bulk of precipitation falling in the southwestern portion of the province. Since the 21st, approximately 20-30 mm of precipitation has fallen across most of southcentral Ontario.

The Provincial Response Centre is forecasting 15-30 mm of rain over the next 5 days for southwestern Ontario.

  • September 1-14: Most stations reported flows below 70% of average using the criterion2 for streamflow.

 

Flood Potential:

  • Immediate flood threat is currently low. Long term flood threat would be from widespread and significant rainfall.
 

Average Historical Precipitation

  • Overall average September precipitation ranges from 50mm to 100mm
  • Most stations range from 75mm to 90mm

Environment Canada Fall Outlook (September-October-November)5

  • Above normal precipitation for the eastern most portion of S. Ontario, normal elsewhere.
  • Near normal temperatures for all of southern Ontario.

MNR Northeast

  • Most stations reported below 70% of the average precipitation expected by the third week of September1 (By the end of the third week, 70% of the average precipitation for August would indicate a trend toward the average for the month). Since the 21st, approximately 35-50 mm of precipitation has been recorded at most stations across the northeastern portion of the Province.

Northeastern Ontario is forecast to receive 10 to 25 mm of rain over the next 5 days, with potential additional amounts falling locally.

  • Most stations reported flows below 70% of average using the criterion2 for streamflow

Flood Potential:

  • Immediate flood threat is currently low. Long term flood threat would be from widespread and significant rainfall.
 

Average Historical Precipitation

  • Ranges from 85mm to 115 mm for September for most stations

Environment Canada Fall Outlook (September-October-November) 5
  • Above normal precipitation
  • Below normal temperatures

MNR Northwest

  • One MNR District is in a confirmed Level I low water condition: Dryden
  • Approximately two thirds of the stations reported below 70% of the average precipitation expected by the third week of September1 (By the end of the third week, 70% of the average precipitation for August would indicate a trend toward the average for the month). Since the 21st, approximately 20-30 mm of precipitation has fallen across most of northwestern Ontario.

Northwestern Ontario is forecast to receive 30 to 50 mm of rain over the next 5 days, with potential additional amounts falling locally.
  • September 1-14: Most stations reported flows above 70% of average using the criterion2 for streamflow

 

 

Flood Potential:

  • Immediate flood threat is currently low. Long term flood threat would be from widespread and significant rainfall. Short term flood threat would be from heavy localized precipitation in repeated thunderstorms.
 

Average Historical Precipitation

  • Ranges from 85 mm to 90 mm for September for most stations.

Environment Canada Fall Outlook (September-October-November) 5

  • Above normal precipitation
  • Below normal temperatures

1Environment Canada’s synoptic stations are equipped to measure snow. Precipitation gauges from dataloggers often are not set up to measure snow adequately. The resulting errors plus the elimination of many of the readings for these gauges means our precipitation coverage is poor during months with snow.
2For each gauge used in the analysis the average flow is calculated for July, and August and September from the historical record. The minimum of these three values is compared to the past month’s average flow. During the winter months most streams are partially filled or covered over with ice. This ice reduces the cross-section of the stream resulting in flow readings that are higher than actual. This error is corrected in the historical record. Thus the observed, relative to the historical minimum, is also higher than the actual in streams with significant ice conditions.
3 Level I conditions initiate the formation of a Water Response Team (WRT) which encourages a voluntary 10% reduction in water use. At Level II the WRT encourages a further 10% reduction by restricting non-essential water use; level III represents the condition where there is insufficient supply of water to meet all needs which July result in regulation of water use.

4Great Lakes summary includes information from Environment Canada, Great Lakes - St. Lawrence Regulation Office and the Detroit District U.S. Army Corps of Engineers.

5Outlook provided by Environment Canada. Environment Canada has assigned very low confidence to this season’s precipitation Outlook across the province and medium confidence to the temperature Outlook.

Brent Smith

Surface Water Monitoring Intern
September 25, 2003