June 20, 2019
I am pleased by the weather the past few days since it is going to be good for the lake to cool down a bit since the 100 degrees we saw on June 12. I was getting concerned we were going to have a spring like last year after several days above 80 degrees in May and the lake temperature increased from 60 degrees to 67 degrees by mid-month. Fortunately the second half of May cooled a bit, which cooled the lake as well.

Temperature has been above normal and precipitation below normal for the second quarter of the year (see images below) which was concerning leading into summer. Both images below represent departures from normal. In the temperature map on the left red and yellow is above normal and green and below below normal. In the precipitation map at right the colors are switched with red and yellow below normal and green and blue above normal. Essentially red and yelow is bad and green and blue is good (if you like rain and cool weather).


However, the climate forecast is for normal or cooler than average summer according to the Oregon Department of Agriculture modeling, which is summarized below by Pete Parsons from ODA:

“Bottom Line: Slightly-below-average temperatures and precipitation are indicated for the 3-month period, but the temperatures forecast has lower confidence than usual. Late July appears to have the best chance for warm weather, relative to average, with August and September having the best chance of relatively cool conditions.”

Cooler weather helps us in several ways; It reduces the amount of river water we have to use to make up for evaporation and irrigation. And cooler air temperature means a cooler lake, which reduces the advantage for cyanobacteria and makes it more likely we will see a more balanced algae population. If conditions are as forecast it will be a departure from the past few years where we have had very hot and dry summers with many days above 90 degrees.

So far though the lake currently is experiencing quite good water quality, with our algae community dominated by diatoms, specifically Stephanodiscus niagarae. The phosphorus level is also quite low, but that will change after opening the headgate on June 10. This is because phosphorus in the river is about 10 times the level in the lake right now. But so far we are experiencing relatively clear water, no cyanobacteria and temperature not too cold for swimming. If it could only stay this way all summer.