Seattle Greenlaker September 12, 2017 6:07am

Photo by Garet Munger

Does Green Lake’s water level seem low? You aren’t imagining it, it really is. We received a tip from Greenlaker Garet Munger who has been monitoring the water level for the past four years. He shared his data and insights with us. 

Green Lake Water Level August 30, 2013 to August 30, 2017

CharlieChester (our mixed cocker and poodle) and I have been making regular, nearly daily visits to Green Lake since moving closer to the lake in 2012.  Most days we make a complete circuit around the lake.  To satisfy my own curiosity, I have been measuring and keeping a record of the water level in Green Lake since August 2013. I measure the level of the water at a fixed point on the dock by the boat rental at the north end of the lake.

As anybody who has visited the lake will have observed, the water level in the lake is currently at a very low level.  By my records, the level today (September 7, 2017) is near the lowest level it has been over the five Septembers for which I have recorded.  The lowest level came on August 28, 2015.  That lowest level was about ½” below today’s level.  In 2015, the water level came up after the 28^th with a storm event that produced about 1 ¾” of rain.

This summer has been an unusually almost record setting year for the lack of rain.  It has also been warmer than average.  The last significant storm event for Seattle was June 16.  Precipitation of almost ¾” fell on Green Lake during that storm.  Since then there was 0.03 inches recorded at Green Lake on July 28, and .11 inches of rain on August 31.

Rain fall is recorded at Green Lake by a weather station installed at the Small Craft Center at Green Lake.  Daily results are published and reported here.

The water level in Green Lake has gone down each day over the summer at a rate of about 1/8” per day.  We can expect the water level to continue receding until the first storm event of the fall.  With higher temperatures, the rate of decline has been closer to ¼” per day.

Over the five years for which I have measurements, the lowest level measured at the beginning of September has varied by almost three inches. To a large extent, these annual differences in summer water levels can be accounted for; by the variation in the amounts and pattern of precipitation over the summer, differences in temperatures, and differences in the water level at the beginning of the summer, and by slight differences in outflows from the lake during the summer months.

Thank you Garet for sharing your citizen scientist skills with us!