Turbidity FAQ – Fall 2025
What is the current climate like in the Henry’s Fork Watershed? We have seen warmer temperatures and less water as a whole in water year 2025. *2025 is currently tied with 2016 for the 4th warmest water year in the 37-year record and the 5th warmest spring and summer in that record. *The total precipitation so far for water year 2025 is 15% less than average. *Precipitation since April 1, 2025, is the 3rd lowest in the 37-year record. *Natural streamflow is 30% less than average. *Island Park Reservoir is 33% full, compared with 47% full on average. What was turbidity like August-September 2025? August Conditions A turbidity event caused by multiple factors occurred in mid-August. Turbidity peaked at 21 turbidity units during this time. September Conditions Turbidity has recently (September 8) fallen back below 10 turbidity units — the lowest level in weeks. This welcome improvement is due to stable weather and reduced outflow, which have allowed sediments and algae to settle. While conditions are still slightly above the ideal turbidity level of 5 turbidity units for dry-fly fishing, it’s a notable step in the right direction. Where is the turbidity coming from? The root of