December 2021

I have archived the December 2021 Water Level Chart (at left), bringing 2021 to a close. Our general goal in December is to get the lake down to about 18 inches by the time it freezes over, without overshooting the mark. We have after all only 24 inches to play with. As it turns out, the lake froze over on December 20th with the lake level down just 1 foot. Precipitation for the month was 3.44 inches, average for December, bringing us to 46.18 inches for the year, 2.12 inches more than average. It is only because of the excessive rainfall we received in July (9 inches) and September (8.5 inches) that we ended the year a bit ahead of average precipitation because for most of the rest of the year, we fell short of monthly averages. And that’s about all I’m going to say about December. It’s a New Year.

One big difference between 2020 and 2021 turned out to be the flushing rates and retention times. In 2020 we had a flushing rate of about 2.3x with a retention time of 140 days. In 2021 the flushing rate was 1.8x (the same as the published rate for Clary Lake) with a retention time of 240 days. This is in effect a measure of the amount of water that passed through Clary Lake: in 2020, a total of 16,632 acre feet of water passed through the lake, in 2021 that figure was  significantly less, only 13,274 acre feet. The lower flushing rate in 2021 very likely had a beneficial effect on water quality.

[UPDATE]: I was so intrigued with the difference in flushing rate and retention time for 2020 and 2021 that I decided to graph them to make the differences more evident. Here’s the result:

I’ll add data for 2022 as it becomes available.

I can’t end 2021 without highlighting an interesting but ultimately useless bit of data analysis I wasted time on this year. Everyone knows that I love charts. If you don’t know that by now, then you simply haven’t been paying attention! I’d like to show you two fascinating but useless charts I made this year. First a bit of explanation. I have long thought it would be cool if I could somehow correlate the flows from Clary Lake with the flows in the Sheepscot River as measured at the Sheepscot River Gaging Station which is located at the foot of Grand Army Hill. It turns out you really can’t correlate the two flows in any reasonable fashion for two primary reasons. First, because the hydrological characteristics of the Clary Lake watershed (9.9 square miles) and that of the larger Sheepscot River watershed (142 square miles) are quite different. Clary should contribute 6.9% of the water measured at the gaging station but that figure actually varied from a low of around 1% to a high of 60% with an average of around 12.4%. Sheesh. Second, nobody actually controls the flows on the river, but we do in fact do control the outflows from Clary Lake so it is largely our own management activities that make correlating the two flows almost impossible. It would be nice if Clary outflows were always 6.9% of Sheepscot River flows, but I guess that would be too easy! Anyways, here are two charts I made while investigating whether a correlation between lake and river flows exists. One shows Clary Flows as a percentage of the Sheepscot River flows. The average turned out to be 12.43%. The other is a simple visual comparison of the two flow amounts which I did to see if anything jumped out at me. Nothing did:

Here’s the 2021 Water Level Chart gallery:

[Show slideshow]

Happy New Year everyone 🙂

Clary Lake has been trying to freeze over for about 3 weeks now, first at one end, then at the other. Each time it’s melted off. A good section out in front of my place has been ice free all along thanks to the ducks that come to our bird feeding station, they splash around and keep the ice from forming. Clary has just been waiting for a good cold night to freeze over, and last night was it. This morning the temperature was a paltry 9.9° F and from all appearances, the lake is now solidly frozen over. There is no sign of ducks today! Historically, A review of our Ice In and Ice Out Dates page shows that 12/20 is on the late side for the lake to freeze over. With the exception of the freak year in 2016 when the lake actually didn’t freeze over completely until January 15th, this is the latest ice-in date since the lake froze over on December 30, 2006. Continue reading →

November 2021

I have archived the November 2021 Water Level Chart (at left). The lake level in November was like a roller coaster ride. Our general plan for a dam operations in November is to get the lake level down a foot or so below the HWM in preparation for the lake freezing over sometime in December. A large rain event on the last day of October however brought the lake up to +0.25 ABOVE the high water mark, the highest the lake has been all year! On the first day of November we pulled one of the three remaining stop logs and opened the gate 1.05 feet to drain off some water which resulted in the lake level dropping 1.18 feet over over the next 12 days. Over the rest of the month we had numerous rain storms including one of 1.22 inches on the 12th and a 1.10 inch storm on the 22nd. This rainfall kept the lake level up higher than we would have liked. We ended the month with the lake level down 1.13 feet. Continue reading →