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Keoka Water Quality

The average Secchi disk reading for 2022 was 6.8 meters, which falls into the moderately clear range. The
average total phosphorus reading of 6.1 ppb falls into the moderate range. The average deep water phosphorus value was not significantly above surface water phosphorus values, which suggests phosphorus recycling is not problematic. The chlorophyll average of 3.5 ppb falls into the moderate range. Long-term trend analysis indicates chlorophyll concentrations in Keoka Lake are stable, total phosphorus concentrations are decreasing, and clarity readings are increasing. The average color reading for 2022 was 23.4 SPU, indicating that water in Keoka Lake is moderately colored.

2022 Water-testing Summary

Keoka Lake’s surface water chlorophyll (ppb), phosphorus (ppb), and Secchi depth (meters) data comparison. Colored areas represent the long-term range of values, from minimum to maximum. Area thickness indicates frequency of measurements at that value. Area thickness increases as more measurements are reported at that value. The vertical black line represents the long-term average value. The large red dot represents 2022’s average value. The small red dots represent individual readings taken in 2022.

2022 average vs. long-term average

  • Clarity: Keoka Lake’s 2022 average water clarity was within the ‘moderately clear’ range. Keoka Lake’s long-term clarity trend is increasing, indicating deeper clarity readings over time.
  • Chlorophyll: Keoka Lake’s 2022 average chlorophyll concentration was within the ‘moderate’ range. Keoka Lake’s long-term chlorophyll trend is stable, indicating that chlorophyll concentrations in the water are neither higher nor lower over time.
  • Phosphorous: Keoka Lake’s 2022 average phosphorous concentration was within the ‘moderate’ range. Deep water phosphorus values were not significantly above surface water phosphorus values indicating that phosphorus recycling was not an issue for Keoka Lake in 2022. Keoka Lake’s long-term total phosphorus trend is decreasing, indicating less phosphorus in the water over time.

Gloeotrichia echinulata (a type of cyanobacteria (blue-green algae) commonly found in low-nutrient waters) can be seen with the naked eye. Gloeo density is reported as a value ranging from 0 – 6, based on the number of Gloeo colonies seen through a Secchi scope. Higher values indicate more Gloeo colonies. On the density chart below, Keoka Lake reached a density of 1; peaking in the month of July.

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