Category Archives: Water Quality

WATER QUALITY

A section from the Lake Level Monitoring report contained in Staff Report from the December 13, 2012 board meeting material.  This section drafted by district staff.

A full water quality report was given in September 2012, so only a summary of that data are provided here. The key aspect of consideration was could the lake level be shown to have negatively or positively impacted the water quality. It had been said at the outset that the water quality question would be the most difficult to answer as it is much more variable and unpredictable especially when dealing with living organism, blue-green algae.

What was apparent from the data set was that while 2012 was a worse year bloom wise from the two previous it was better the 2008 and 2009 when the lake was higher and warmer.

A cursory review of past blooms indicate that 2012 was not the first year we have seen a lake wide bloom. These occurred in 2008 and 2009 certainly, but aerial photographs from the 1990’s show similar events occurring. Bloom constituency was different then, as the more toxic Anabaena and Microcystis dominated the lake compared to the significantly less toxic Gloeotrichia that was the major continuant of the recent bloom. Continue reading →

Adored in Fenway, Not in Lincoln City

Since we have now made it to the end of the 2012 recreational season it’s time to make a few observations. The season began with two public hearings; the first in May and a second in June where record numbers of the public provided comment on summertime lake levels.  At the conclusion of these sessions the board voted to change the target summertime lake level from 9.6 to 9.0 which began on June 15^th.  In the August board meeting the board established an ending summer lake level target of 8.8 to accommodate the terms of the Districts impoundment permit.  The current lake level is at the 8.8 target.  In a week the District will remove what remains of the impoundment structure.

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As a result of this decision we know by observation that the lake was much lower this year.  We know this lower level impacted people as we got many reports from lake uses on how this lower lake level negatively impacted their boating experience.  There was however a more significant, more noticeable contrast in the lake this year from previous years. What happened to our lake this year?

On July 26^th the District delivered the first Harmful Algal Bloom Surveillance (HABS) report by email as the season’s historic Blue-Green Algae bloom began.  This bloom quickly grew into large patches of thick green goo floating around the lake.  Early morning visitors to the lake this summer saw significant levels of floating algae over the entire surface of the lake.  Significant suspended algae can be found in the water column at almost any location on the lake on any day this summer.  Universally residents around the lake communicated their observations that they had never seen water that was in worse shape than this year.

Despite the terrible condition of the water, the lake was never posted beyond a moderate risk.  That is because the board changed their methodology for posting where one sample taken at Sand Point on August 28th exceeded cell count standards but did not exceed microcyctin parameters.  I support these new guidelines because they are now based on microcyctin levels, there is no real reason to scare the public if there are no toxins in the water threatening their health.  This year even though the lake looked terrible, the microcystin levels never topped .9ppb when over 8ppb is the health Department threshold.  The mess did however impact most people’s enjoyment of the lake, who would be covered with green dots as they exit the water.  So while not toxic the algae was very bothersome.

Another observation this year is related to the temperature of the lake.  According to the District’s own measurements the lake saw a 3% increase in the temperature this summer over last summer when levels were higher.  This spring, many predicted that lake temperatures would rise with lower water levels.  It appears that that this did occur.  With different weather this difference in lake temperature could have been more dramatic as average air temperature for Lincoln City were 2% lower this year when compared to the previous year. Lincoln City experienced similar amounts of rainfall during the period of impoundment with 1.6” in 2011 and 1.8” in 2012.  This is illustrated in the charts below, click for a larger version.

Devils Lake Temperature
Lincoln City Temp	Lincoln City Precip

There was a presentation given to the Board of Directors at the September meeting which characterized this summers results somewhat differently than we have here.  Let just say that we see the situation from a different viewpoint.  So in conclusion we cannot say with absolute certainty that the lower lake levels authorized by the DLWID board resulted in the observed higher temperatures and higher levels of summer green algae.  It can be said that the board decision on lake level did nothing to improve water quality this summer.