May 2016

I’ve archived the May 2016 Water Level Chart (at left). The most notable features of the May chart are the lack of rainfall for the month and the inexorable fall of the lake level despite the gate having been mostly closed on the afternoon of Thursday, May 19th. In fact, after the gate closure, there was almost no noticeable reduction in the rate at which the lake lost water during the month (0.025′ before vs. 0.019′ after). The lake level started out at -47.88″ below the top of the dam and fell an average of only 0.02′ per day (less than 1/4″) ending up at -55.68″ below the top of the dam, for a total loss of -7.8″. The lake fell 28 out of 31 days during the month while remaining unchanged on only 3 days. Not once during the month did the lake level rise. 

I wrote about the gate closure back on May 21st (see: “Clary Lake Dam’s Gate Almost But Not Quite Closed“). I presume the dam operator left the gate partly open to maintain minimum outlet flows as required by the Clary Lake water level order, but clearly the gate was left open too much: in my estimation, net outflows (including evaporation) have exceeded inflows by as much as 5 CFS (Cubic Feet per Second). Any way you look at it, the simple fact that the lake level continues to fall indicates the gate opening is too great: minimum flows are never supposed to exceed inflows. For more information about minimum flows and where they come from see Minimum Flows Explained.

Average rainfall for May is around 3.7″ but we received only 1.79″ of rain for the entire month, considerably less than 1/2 the normal amount. Less precipitation means less runoff obviously; it is likely that if we’d been receiving the normal amount of rain for the month that the lake level would have more or less stabilized once the gate was lowered.

April 2016

I’ve archived the April 2016 Water Level Chart (at left). The most notable feature of the April chart is that the lake level stayed pretty stable around -34″ below the top of the dam for the first 15 days of the month (despite the dam’s gate being wide open) after which point it began to fall steadily, ending the month at -47″ below the top of the dam. All in all we received only 3.33″ of rain in April which is less than the average monthly precipitation of 3.78″. This lack of rainfall has contributed to the dry conditions we’re seeing now. Most of the rainfall occurred in the first half of the month, with 2.68″ falling by April 15th which explains the relatively stable water level during that time. Only an additional 0.65″ fell during the second half of the month.

I’ve added a new statistic to the monthly water level chart, that being the volume of Clary Lake at its current level as a percentage of full. This new data has been added to the middle “narrative” portion of the Current Water Level Charts page. The figure comes from a volume analysis I’ve been working on this past winter based on the Clary Lake Depth Chart (at left) that I prepared from data collected by DEP during their September 2012 bathymetric survey and additional [the_tooltip text=”LIDAR” tooltip=”Lidar (also written LIDAR, LiDAR or LADAR) is a surveying technology that measures distance by illuminating a target with a laser light. Lidar exists as an acronym of Light Detection And Ranging. LIDAR data is typically collected from planes.”  url=”” background=”” color=””] data I obtained from the Maine Office of GIS. In theory calculating volumes from a contour map is pretty straight forward and is a task most land surveyors are familiar with, but the size of Clary Lake presented some challenges and there turned out to be a considerable learning curve to the GIS software I used to extract the information I needed for my calculations. I finally got it figured out.

Currently, at -47″ below the top of the dam, the lake is about 66% full and the area has shrunk to about 473 acres of about 62% of its size when full. Continue reading →

March 2016

I’ve archived the March 2016 Water Level Chart (at left). The most notable thing about the March water level chart is that while the lake level has been generally falling since the beginning of the month, it has still been significantly higher throughout the whole month- indeed, throughout the whole winter- than in any of the last 5 years. Part of this is due to a very early ice out (March 13th) and above average rainfall for the first 3 months of the year. The dam’s gate has been wide open since January 4th. As high as it has been, it has still been generally lower than the lower-limit (2′ below normal high water mark) specified in the Clary Lake water level order.

I spoke to David Hodsdon the other day about resuming our water quality monitoring activities. He’s going to send the Association’s YSI Pro20 digital dissolved oxygen meter off to be calibrated tomorrow (a yearly VLMP requirement) and as soon as we get it back we’ll set a date to hit the lake and start collecting data again. To that end, I launched my boat this morning- the earliest I’ve ever gotten it in the water. We try to collect data every 2 weeks during the recreational boating season, typically between mid-April through October. This will be David’s 40th year as a Volunteer Lake Monitor. Way to go David!