Lake of the Woods Control Board Historical Graph Revisions

June 15, 2009 - Statistical Level/Flow Data Updated

 
The water level and flow statistical percentile data on the historical graphs have been updated to the 30 year period 1976 to 2005. Previously the reference period was 1970-1999. As with the previous period, some percentile data have been based on simulation model results to account for the impacts of the new rule curves on Rainy and Namakan lakes, which were implemented by the International Joint Commission on January 6, 2000. The data affected are the percentile data for Namakan Lake outflows and Rainy Lake inflows & outflows. Lake of the Woods inflows are not affected, although they were in the 1970-1999 period.

In addition, Namakan Lake inflow and outflow data now starts in 1941. Previously it was only available back to 1956.

 

October 1, 2000 - Statistical Level/Flow Data Updated

 
The water level and flow statistical percentile data on the historical graphs have been updated to the 30 year period 1970 to 1999. Previously the reference period was 1963-1992. In addition, some percentile data have been based on simulation model results to account for the impacts of the new rule curves on Rainy and Namakan lakes, which were implemented by the International Joint Commission on January 6, 2000. The data affected are the percentile data for Namakan Lake outflows, Rainy Lake inflows & outflows, and Lake of the Woods inflows. Lastly, the percentile data shown on the graphs are now computed and plotted on a ¼-month basis rather than ½-month.

The change from ½-month to ¼-month percentiles and reporting periods should more accurately reflect variability and trends in levels and flows. While there may be more volatility in inflows, especially for the larger lakes, changing trends in current inflows should be identified sooner. The actual elevation data are 3-day mean water levels plotted every ¼-month and are now compared to the new ¼-monthly percentiles for historical comparison. The actual inflows used for comparison to historic are now ¼-month averages instead of ½-month averages, and are plotted in the centre of each ¼-month period. Outflow data are still daily average values plotted daily; the outflow %iles are ¼-monthly outflow average values plotted ¼-monthly.
 

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