September 2017 Water Level Chart Archived

9 waterlevelchart_September2017I have archived the September 2017 Water Level Chart (at left). The most notable feature of the September chart is how little the lake level changed over the course of the month: the lake level dropped only 1.56″ from the first day to the last. This didn’t appear to have much if anything to do with the 2.4″ of precipitation received since the lake barely rose after receiving that rainfall. With effectively no water leaving the lake through the channel for the past several months, likely all of the drop (an average of less than 1/10th of an inch per day) was due to evaporation. The lake reached -58.68″ below the normal high water mark on the last day of the month, the lowest level reached so far this year.

We received only 2.37″ of rain in September (average is 3.74″ for the month) bringing us to 23.65″ for the year which is fully 6.28″ shy of where we should be at this time. According to the National Integrated Drought Information System we’re in MODERATE drought, not as dry as we were last year at this time, but still pretty dry.

Looking at September in light of the lake level trend for the year, the lack of rainfall in 2017 has resulted in a slow but steady decline in water level without any of the ups and downs usually present due to normal precipitation. This lack of “volatility” over the spring and summer is especially noticeable on the Water Level Chart covering the period December 2011 through the current date (above). From December 2011 until the spring of 2015, the lake level during the summer fluctuated up and down considerable whereas since the spring of 2015, after reaching a high in April, the lake level has pretty much steadily fallen to it’s low in October. In 2015, 2016, and so far in 2o17, precipitation has been significantly below average.

This year, the lake reached a high of -8.76″ below the normal high water mark on April 13th, thanks in part to the effort of some beavers who managed to at least partially plug up the dam outlet. This was the highest water level we’ve seen in SEVEN YEARS, since 2010. On a marginally bright note, the lake level effectively bottomed out this year about a foot higher than it did last year. I attribute this to profuse vegetation in the channel which has hampered lake outflow.

While the lack of rainfall has been hard on people’s gardens and wells, the lack of rainfall and resulting runoff has been generally good for Clary Lake’s water quality which has maintained better than average transparency throughout the summer in spite of the drastically low-water conditions. Secchi disk readings this summer never once fell below 3 meters (see our Clary Lake Water Monitoring Data page). David Hodsdon and I are heading out later this morning to collect more water quality data and I expect transparency to have improved even further.

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