In preparation for the navigation season, the district’s Fountain City, Wis., survey crew began annual Lake Pepin ice measurements Feb. 15.
The first ice measurements the crew recorded were eight to 10 inches thinner than last year, said Mark Upward, operations. He added that there were only two measurements taken this year compared to the five last year. Annual ice measurements on Lake Pepin are used to predict the navigational outlook on the Mississippi River. This year’s measurements indicate the navigation season starting sooner than previous years.
Since the district began taking measurements in 1998, the crew has used the same techniques. Three people are typically needed for each survey, two people on the ice and one on land to record data and follow the crew. The surveying crew uses an airboat, a portable global positioning system to identify the exact location for taking measurements and a tape measure to determine the ice thickness. The general ice condition is also recorded.
Despite the mild winter weather, the season could not open until maintenance repairs were completed at Lock and Dam 7, near La Crosse, Wis. The district completed the repairs March 12, and the lock welcomed the first tow soon after, said Delene Moser, Lock and Dam 7 lockmaster.
The navigation season officially began last year on when the first tow, Motor Vessel John M. Rivers, broke through Lake Pepin on March 31, 2011 on its way to Pool 2, near Hastings, Minn. The average opening date of the navigation season in St. Paul for the last 10 years is March 20. For many of those who live in the Midwest, the first tow of the season is the unofficial start of spring, said Upward.
Ice measurements are dependent upon weather conditions, but are normally collected weekly until navigation season begins. The information is posted on the district’s website. Click here for figures on past and present Lake Pepin ice measurements.