If you’ve been on Lake Minnetonka lately, you’ve probably noticed a change on the Jake as the water level continues to drop due lo lack of rainfall and daily evaporation loss. How unusual it is for Lake Minnetonka water levels to fall, and what does the lack of rain have to do with it?
At the same time, anyone who has walked, run, or biked past Minnchaha Creek this summer must be wondering what has happened to this beautiful urban stream? Who turned off the faucet on the majestic Minnehaha Falls that people like to show off to their family and friends from out of town? What will happen lo the wildlife mat relies on the creek as their home? When can people canoe the Creek again?
These are just some of the questions the Minnehaha Creek Watershed District (MCWD) has been receiving on a regular basis over the summer.
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| A completely-dry Minnehaha Falls on July 16 2009 |
The Minnehaha Creek headwaters at Grays Bay Dam closed early on June 2 due to low lake levels on Lake Minnetonka. And visitors to the historic Minnehaha Falls in Minneapolis last month were surprised to see it actually had rim dry.
The main reason for the lack of water is, well … lack of water.
The Twin Cities metro area is in dire need of rain. This region of the state is considered to be in a moderate to severe drought. According to the Minnesota State Climate the Twin Cities is in a long term precipitation deficit of 14.16 inches thai began over a year ago in May of 2008. The 30 year average normal rainfall amount from January through July is 17.62 inches of precipitation. The Twin Cities area has only received 10.13 inches of rain from Jan. 1 to July 31, 2009. That is 7.49 inches below normal amounts.
Grays Bay dam is the outlet of Lake Minnetonka. It is an adjustable structure that controls Lake Minnetonka levels and discharge to Minnehaha Creek. According to the dam operating procedure, the Grays Bay dam closes when the lake level is at or below 928.6 feet above mean sea level. This water level was mandated by the DNR back in 1979 as this was the lowest point on the original structure that was in place before construction of the current darn.
On July 30, 2009, the lake level was at 927.86 feet or 8.88 inches below the required value. Even more shocking is the fact lhat Lake Minnetonka is more than 18 inches below the typical ordinary high water level of 929.4 feet. The dam was closed on June 2, 2009, when the lake dropped to 928.56 feet above mean sea level. In order for the MCWD to open the dam at Grays Bay, bringing water back to Minnehaha Creek, the water level in Lake Minnetonka has to rise 8.88 inches. On the hot, breezy dog days of summer, evaporation alone lakes away approximately 70 million gallons of water per day on Lake Minnetonka, which translates to almost 2 tenths of an inch of water.
The Grays Bay dam is opened after ice out on Lake Minnetonka in mid to late April. The dam usually remains open with adjustments in the amount of water released or discharged lo the creek depending on the lake level and stream capacity throughout open water season. Since 1997, the closure of the dam has most often occurred in laic August to early September or even sometimes as late as December. There have been a couple of exceptions. In 20011, the dam “was closed for the entire open waler season because lake levels never rose above 928.6 feet. The lake levels .that year were as low as 927.37 feet or almost 15 inches below required darn opening level. In 2007 the dam was closed on July 23 and remained closed unlil a large amount of rain during the late summer and early fall provided enough rain to reopen the dam on Oct. 8, 2007. It remained open for A couple of weeks before closing again in November.
It’s going to take a lot of rain to bring Lake Minnetonka water levels up again. The first week of August has brought some needed rain to the Twin Cities. The rain events of Aug. 2, 7 and 8 have produced a total of 3.48 Inches of rain that has resulted in an increase of 3.24 inches in the lake level of Lake Minnetonka. The lake level was 928.07. Comparing past rain events in relationship to increasing water levels in Lake Minnetonka for previous years, it would take approximately 10 to 11 inches of a good slow soaking rain stretched over many days to help with ihe current condition.
When the Minnehaha Creek Watershed District gets calls from the public, the best they can do is to reassure them that the creek will flow again. The wildlife will survive and return to their homes, and, yes, you will be able to canoe the creek and bring your family and friends down to the beautiful historic Minnehaha Falls. If asked when, the only thing that can be said is that it’s entirely up to “Mother Nature” to decide.
For more information about the Minnehaha-Creek Watershed District visit the website at: www.MinnehahaCreek.org.
Yvelte Christianson, M.5., is a Water Quality Technician for Minnehaha Creek Watershed District. Udai B. Singh, Ph.D., PX is the Senior HydroSogist/Water Quality Specialist for the Minnehahu Creek Watershed District.
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