Tonka falling fast, no wake rules lifted next week?

Our drier weather pattern is finally causing area lakes and rivers to recede.

With several dry, sunny days in the forecast, the pace of falling lake and river levels will pick up in the next few days. If the dry forecast holds, that could mean Lake Minnetonka will reach a level where "no wake" rules could be removed as early as next week.

Data from the Minnehaha Creek Watershed District shows the level of Lake Minnetonka has dropped over 6 inches from the record high of 931.11 feet above sea level reached on June 23.

According to the Lake Minnetonka Conservation District, the high water emergency, and some wake restrictions, on Lake  Minnetonka will be lifted when the lake level reaches 930.30 feet above sea level for 3 consecutive days. That means the popular west metro lake must fall another 3 inches for LMCD to pull the trigger on removing the high water emergency.

Forecast: falling lake levels

Little or no rain, abundant sunshine and high evaporation rates are likely the next 5 days in the Lake Minnetonka watershed. Hydrologists use complex models to estimate lake and river levels. All factors going into the lake level equation through Sunday right now favor rapidly falling lake levels.

On warm sunny days with a breeze and low dew points in the 50s, evaporation rates are high. We can easily evaporate about a quarter of an inch of moisture from soils each day through Sunday.

Evaporation alone should cause lake levels to drop about an inch by Sunday. Combine the rapid discharge from Lake Minnetonka into Minnehaha Creek of over 300 cubic feet per second, and this forecaster thinks Tonka's lake level could fall to the magic 930.30 foot level by late this weekend or early next week.

Barring any unexpected major downpours, that may mean some of the no wake restrictions could be lifted as early as next week.

There is a chance that some rain will return early next week.

Long range outlook

Given "average" rainfall over the next few weeks, the watershed district's engineering firm estimates lake levels would return to the "ordinary high water" mark around mid- to late August.

Water Level Projections

Water levels are expected to remain high for some time. The District’s engineer, Wenck Associates, has developed a report estimating how long it may take to lower the Lake Minnetonka level to the Ordinary High Water Level (OHW) of 929.40 given normal precipitation events. Assuming normal weather conditions for the rest of the season, the District’s engineer now estimates Lake Minnetonka would not reach a normal goal elevation until mid-to-late August. See attached graph for details.

If the drier forecast for the next few days manages to hold through next week, our area lakes and rivers may continue to fall faster than expected.

Stay tuned.