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Friday, Apr. 29, 2016

Lake gives clues to droughts past and future

Monday, November 26, 2001

A question that has been recently asked is "Are we currently in a drought pattern with respect to Storm Lake?"

In order to answer this question, I have studied lake elevation levels going back to 1931. These levels were taken by county engineers, and I want to thank Darel Burns for giving me copies of the lake elevation data.

The data indicates that the lake has been through three major periods of low water conditions where the water level at times was 36 inches or more below the top of the outlet dam. The 36 inch level is critical when going into the winter on a lake that has a normal 80 percent depth of eight feet. A two-foot ice cover would allow about three feet of water for the fish to swim.

Just before the beginning of the first drought, the water elevation on June 15, 1932, in respect to the top of the dam, was 0 inches or just at the top of the dam. On September 4, 1941, the water level was at a low of 56 inches below the top of the dam. On May 21, 1944, the water level had recovered, and was six inches above the top of the dam. During this drought, the water was below dam level for ten years. No water elevation reading was taken in 1933. Years that the water level was 36 inches or more below the top of the dam at the last reading taken for the year were 1936, 1937, 1939, 1940 and 1941. These water level readings resembled an "S" pattern as they fell above, on, or below the 36 inch water level.

Just before the beginning of the second drought, the water elevation on April 4, 1955, in respect to the top of the dam, was six inches above the top. On December 1, 1958, the water level was at an all time low of 76 inches below the top of the dam. On June 11, 1962, the water level had recovered, and was one inch above the top of the dam. During this drought, the water was below dam level for nearly seven years. Years that the water level was 36 inches or more below the top of the dam at the last reading taken for the year were 1956-1960. These water level readings resembled a "V" pattern as they fell above, on, or below the 36 inch water level.

Just before the beginning of the third drought, the water elevation on July 4, 1975, in respect to the top of the dam, was three inches above the top. On August 3, 1977 and October 4, 1977, the water level was at a low of 48 inches below the top of the dam. On March 27, 1979, the water level had recovered, and was six inches above the top of the dam. During this drought, the water was below dam level for nearly three and a half years. Years that the water level was 36 inches or more below the top of the dam at the last reading taken for the year were 1976 and 1977. These water level readings resembled a "V" pattern as they fell above, on, or below the 36 inch water level.

On July 6, 1999, video documentation shows water flowing over the top of the dam. The estimated elevation was about one inch above the top of the dam. The estimated elevation was about one inch above the top of the dam. On November 3, 2000, the water was at a low of 32 inches below the top of the dam. As of November 4, 2001, the water was 16 inches below the top of the dam.

The current dry spell has not reached the 36 inch level yet. The current projected pattern is downward, and it remains to be seen if it will again challenge the 36 inch level and establish an "S" or "V" shape drought pattern.

Mike Brecher is a Storm Lake lake watcher, and a contributor to the Pilot-Tribune.



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