If anything was going to catch your attention, NASA' Earth Observatory did with a photo from their Landstat9 satellite showing a very green cast to Clear Lake. The story author's take away was that Clear Lake in Lake County California has so much nutrient in its water column that the lake has a runaway algae bloom and went on to describe potential negatives. Social media had so much to say about this, that visitors on the following holiday weekend were nil. They just stayed away.
Look at what they missed, people who did spend time on at the lake were enjoying a fantastic weekend in what was a low bloom, clear, lake. One airplane owner was so incensed by the NASA' slight on Clear Lake's condition that a photo was taken at 10 thousand feet to show the lake was clear. So what's up, was a mistake made or did NASA do a number on rural Lake County? Well, maybe a little of each.
Taking pictures of the earth from space is so common that tens of thousands have been taken from satellites in orbit for everything from weather prediction to pollution detection. By using specialized analysis of the long wave infrared radiation coming off earth from the sun's heating; algae, mineral deposits, fires, temperature variations such as urban heat islands and many other features can be tracked. These infrared images are not in a visible light spectrum so a color is assigned to each specific wavelength. Even Clear Lake was analyzed this way in a study using photos from the Landstat7 satellite back in 2015.
The Clear Lake project led by the Water Resources Department was commissioned by the County Board of Supervisors to track nutrients such as phosphorus that might be coming into the lake and creating algae blooms. Several images were selected from the satellite's photo files and with consultation with the image interpreting company Blue Water Satellite, the lake was analyzed for phosphorus, phytoplankton, cyanobacteria and other wavelengths. A color was assigned to the images to separate the target wavelengths from an otherwise clear condition.
Results were very revealing. Most of the phosphorus laden sediment came in from Middle Creek, but a significant amount also arrived via Big Valley creeks. The sediment containing phosphorus goes directly into the lake without the removed marshy wetlands acting as settling basins. The lower arms of the lake had little input. All of this data was available because of a county-wide storm with steady rainfall for 5 days and then a clear day photo was available on the 6th showing the results. Additional analysis from spring, summer and winter photos also showed windy days re-suspend nutrients from the bottom creating a bloom and drives it toward the East end of the lake. Hot summer days are definitely the best days for blooms and the only way to determine if there are harmful toxins is by directly testing the water. The local tribal testing have found that.
It's since also been found, that lakes can recycle old phosphorus from the bottom sediments during hot summer months adding to fresh material from the winter. Its little wonder algal blooms can be significant during certain summers. But for exceptional days, all this can go unnoticed on the surface of the lake. The satellite picks up the infrared wavelengths from looking into the water column several feet and this magnifies results, making every day look exceptional.
Yes, this is a very good tool to estimate the processes of a lake and its condition, even if it's not apparent from the surface. That fact was left out of the news story about the landstat9 photo which posted what they called a natural color image from May15, 2024 [I just wonder how much of NASA's photo was color enhanced for green] and then speculated about its negative meaning. The author made much of a single photo without a ground truth of the results. Like any lake, to determine harmful toxins the tests must be on the lake and not from a satellite photo.
Jim Steele's background includes; Former County Supervisor, retired State Freshwater Ecologist and Consultant. He managed and investigated fish restoration and protection projects in marine, freshwater streams and lakes of California for over four decades.
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