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Estuarine Turbidity Maxima Watch
This ETM Watch provides images useful for predicting the timing of the ETM today and provides historical context for understanding the patterns of ETM timing and intensity at SATURN-01 and SATURN-03.
ETM here is defined as periods during which turbidity exceeds the 80th percentile of observed turbidity for that tidal day, with periods of lower turbidity of less than 15 minutes in between periods of high turbidity counted as part of the ETM period.The ETM is predicted to occur at the SATURN-01 and SATURN-03 station locations at roughly the same time each day (time relative to the high water before the lower low water (LLW)).
Over the history of these stations, this prediction is accurate approximately 80% of the time. If the ETM is observed in the ebb before or flood after the LLW, the chance that it will occur again at the same time of the tide on the following day is >90%. If the ETM is observed in the ebb and flood surrounding the higher low water (HLW) the pattern of recurrence is less reliable. For each station, there are two different ways of viewing the turbidity data, each with two options :
- Timeseries of recent data with predicted and observed ETM periods. (8 Hours or Tidal Day)
- Observations for turbidity and salinity plotted over observed (solid pink) and predicted (hashed blue) periods of ETM. The timeseries can be viewed either for a full tidal day (today, yesterday, or the day before yesterday), or zoomed in on the last 6 hours and the next 2 hours (with the equivalent 8 hour periods available for yesterday and the day before yesterday). Time series image for today will only show the predicted ETM timing (hashed blue) because the calculation to determine the observed ETM period requires a full tidal day of turbidity data.
- Tide phase plots of turbidity over a 3 month period. (Last 90 days or 3 Month Period)
- (Top plot) The y-axis is hours since the HW before the LLW and the color is determined by the observed turbidity. The displayed SATURN-01 turbidity data is the maximum turbidity observed below 15m. (Bottom plot) A plot of tide elevation data from the NOAA-COOPS station at Tongue Point in Astoria. The tide phase plots can be viewed either over a fixed calendar of 3 month periods, or for the last 90 days.