In 2014 the USGS released a report on turbidity in the upper Esopus, both above and below the Portal, in light of the ongoing controversy between the city's DEP and local communities over it.
The study took in data both from in situ instruments on the creek and the analysis of samples in the laboratory over the three years prior, the former of which it found better at measuring suspended sediment concentrations (SSC) in the water.
Instruments were placed both on the Esopus and several tributaries above the reservoir.

The study sought to determine if it was possible to discern what the sources of turbidity in the Esopus might be, and if possible what those sources were.
It found that Stony Clove Creek was the largest source of turbidity and suspended-sediment concentration, accounting for more turbidity than the rest of the upper Esopus watershed combined, with those two quantities varying directly with each other and also correlating with discharge.
Those loads were markedly higher in 2012, which the authors attributed to the work done to channelize that stream near its mouth in Phoenicia that year in the wake of the flooding caused by Irene.
Woodland Creek, which also empties into the Esopus at Phoenicia, was the second-largest source.

Another USGS study, in 2015, considered what effect the turbidity might be having on fish populations in the upper Esopus.
The authors collected data from 18 100-metre (330 ft) reaches, 10 on tributaries from the Birch to the Little Beaver Kill, and the others on the main stem from Oliverea to Boiceville annually between 2009 and 2011, primarily counting the brown trout, rainbow trout, slimy sculpin and cutlips minnow.
They found some effects downstream of the portal, such as lowered density and biomass, but none significant and none that they considered negative.
Another 2015 study, that took in the effect of the Irene-induced floods found that rainbow trout were the only species in the stream to have been negatively affected by them, for at least two years after the storm, although populations had been trending down for two years before; A fourth study that year which also considered that species population found that that species' density and biomass were higher in the upper Esopus than they had been since before 2010.

The USGS station along the creek near Mount Marion, between Kingston and Saugerties, collects turbidity data every 15 minutes.
The maximum daily SSC mean was 439 mg/L in July 2014, and the minimum was 1 mg/L over four days seven months later.
In September 2015 the maximum and minimum daily suspended sediment discharge was recorded: 6,200 tons (5,600 t) on September 30, and 0.23 tons (0.21 t) on September 8–9, respectively.
Since 2013 the Lomontville station, above Kingston along the lower stream, has also been collecting turbidity data.
Its maximum daily mean for SSC was 210 mg/L in March 2014, and the minimum was less than 1 mg/L on many days from 2014 to 2015.
Maximum daily suspended sediment discharge was 770 tons (700,000 kg) on September 30, 2015, and the minimum was .01 ton (9.1 kg) in October 2014 and May 2015, respectively.

In 2011 a study of the lower Esopus found no significant effect on benthic macroinvertebrates (BMI) at several points in the stream over the previous four years, the period when complaints about the turbidity caused by the reservoir releases began.
Samples were taken both under normal flow conditions and storm discharges.
In addition to BMI, they showed no effect on other metrics such as turbidity, total dissolved solids or dissolved oxygen that correlated to distance from the reservoir.
A 2019 study of the BMI population in the upper Esopus found that although it had declined severely after the floods from Irene and Lee, it had mostly recovered within a year.
In 2014 the USGS released a report on turbidity in the upper Esopus, both above and below the Portal, in light of the ongoing controversy between the city's DEP and local communities over it. The study took in data both from in situ instruments on the creek and the analysis of samples in the laboratory over the three years prior, the former of which it found better at measuring suspended sediment concentrations (SSC) in the water. Instruments were placed both on the Esopus and several tributaries above the reservoir.
The study sought to determine if it was possible to discern what the sources of turbidity in the Esopus might be, and if possible what those sources were. It found that Stony Clove Creek was the largest source of turbidity and suspended-sediment concentration, accounting for more turbidity than the rest of the upper Esopus watershed combined, with those two quantities varying directly with each other and also correlating with discharge. Those loads were markedly higher in 2012, which the authors attributed to the work done to channelize that stream near its mouth in Phoenicia that year in the wake of the flooding caused by Irene. Woodland Creek, which also empties into the Esopus at Phoenicia, was the second-largest source.
Another USGS study, in 2015, considered what effect the turbidity might be having on fish populations in the upper Esopus. The authors collected data from 18 100-metre (330 ft) reaches, 10 on tributaries from the Birch to the Little Beaver Kill, and the others on the main stem from Oliverea to Boiceville annually between 2009 and 2011, primarily counting the brown trout, rainbow trout, slimy sculpin and cutlips minnow. They found some effects downstream of the portal, such as lowered density and biomass, but none significant and none that they considered negative. Another 2015 study, that took in the effect of the Irene-induced floods found that rainbow trout were the only species in the stream to have been negatively affected by them, for at least two years after the storm, although populations had been trending down for two years before; A fourth study that year which also considered that species population found that that species' density and biomass were higher in the upper Esopus than they had been since before 2010.
The USGS station along the creek near Mount Marion, between Kingston and Saugerties, collects turbidity data every 15 minutes. The maximum daily SSC mean was 439 mg/L in July 2014, and the minimum was 1 mg/L over four days seven months later. In September 2015 the maximum and minimum daily suspended sediment discharge was recorded: 6,200 tons (5,600 t) on September 30, and 0.23 tons (0.21 t) on September 8–9, respectively. Since 2013 the Lomontville station, above Kingston along the lower stream, has also been collecting turbidity data. Its maximum daily mean for SSC was 210 mg/L in March 2014, and the minimum was less than 1 mg/L on many days from 2014 to 2015. Maximum daily suspended sediment discharge was 770 tons (700,000 kg) on September 30, 2015, and the minimum was .01 ton (9.1 kg) in October 2014 and May 2015, respectively.
In 2011 a study of the lower Esopus found no significant effect on benthic macroinvertebrates (BMI) at several points in the stream over the previous four years, the period when complaints about the turbidity caused by the reservoir releases began. Samples were taken both under normal flow conditions and storm discharges. In addition to BMI, they showed no effect on other metrics such as turbidity, total dissolved solids or dissolved oxygen that correlated to distance from the reservoir. A 2019 study of the BMI population in the upper Esopus found that although it had declined severely after the floods from Irene and Lee, it had mostly recovered within a year.
Esopus Creek