BY FORREST ADAMS [email protected]

It’s annually ranked among the best lakes in the entire Twin Cities for water quality, and this year's watershed district report card is no different.

Christmas Lake earned an A, though that’s nothing new. In the years 2000 and 2010 and each year in between, the Minnehaha Creek Watershed District gave Christmas Lake an A, rating it “exceptional.” The only decrease was from an A to an A- grade in the year 2004.

The grades are based on three factors the watershed district measures in lakes throughout the summer. One is the total phosphorus measure. High levels of phosphorus are closely related to increased algae, frequency of algae blooms and the increased quantity of blue-green algae. The second is the amount of chlorophyll-a, or the green pigment, in plants. A measure of its presence in water estimates algae abundance. The third is Secchi disk transparency. A black and white Secchi disk is lowered into the water, and the lower the Secchi disk is visible, the clearer the water.

Lower levels of algae and chlorophyll-a and higher Secchi disk visibility are good qualities in a lake.

Kelly Dooley, lakes water quality technician for the watershed district, said measurements that contribute to the final grade are taken twice each month in each the district’s 53 lakes beginning in mid-April and ending in late October/early-November.

She thinks a reason for the consistently high water quality in Christmas Lake is due to several factors. One is that it’s deep at 87 feet. The other is that it’s large and allows for water the water to disperse. Perhaps the most important is that it is not surrounded by dense residential housing. Dooley said other factors that contribute to lake condition include aquatic plants, fisheries, harmful chemicals and lake over-use. Not having the high-density housing near the lake is beneficial because it limits the likelihood of chemical runoff and lake over-use.

News of the good grade on Christmas Lake was welcomed by Joe Shneider, president of the Christmas Lake Association. Now beginning his first year in the position’s three-year term, Shneider confirmed that Christmas Lake has good water quality.

You might say it’s something lake residents are proud of.

The lake association contracts with Blue Water Science to monitor the lake’s water quality. The recent Blue Water report was prepared in March 2011 and contains multiple data points, some of them dating all the way back to 1887. Shneider brought out a data summary and trend analysis that quantifies just how good the water really is and said the challenge facing homeowners now is to keep their lake clean and free from any new invasive aquatic species while at the same time not aggravating what’s already in the lake.

“We’re trying to educate our lake homeowners,” Shneider said. “It’s our responsibility to maintain the lake and leave it better than when we got it. The question is, ‘Are you doing enough?’ It’s really hard to say, but we believe strongly that we are doing what we can.”

Christmas Lake is only partially in Chanhassen. Most of the 276-acre body of water is in Shorewood.

Lake Minnewashta, the other Minnehaha Creek Watershed District lake in Chanhassen, also received a high grade on its report card. The water in Minnewashta consistently grades as a B+, which is just below Christmas Lake, but is still higher than many other lakes, said Dooley.

For the past five years, the Christmas Lake Homeowners Association has recommended that nobody use chemicals on their lawn. Shneider said in an effort to prevent zebra mussels from coming into Christmas Lake, he hopes to somehow initiate more control over the public access. The lake association is participating this summer in a pilot project through the watershed district to introduce more native weevils into the lake that will eat the non-native Eurasian water milfoil, according to Shneider.