Water Column Clarity
Water clarity was measured at seven locations in the Providence and Seekonk Rivers on July 15, 2020. On the day prior to the survey, 0.82 inches of precipitation was recorded. Average Secchi depth decreased by 0.23 m since the last survey, from 1.77 m to 1.54 m. Water clarity increased at Edgewood Yacht Club (0.13 m); decreases in water clarity were observed at all other sites. The greatest decrease in clarity was observed at Phillipsdale Landing (-0.73 m). The greatest water clarity was observed at Pawtuxet Cove, which had an average Secchi depth of 1.90 m. Lowest water clarity was observed at Phillipsdale Landing, with a measured Secchi depth of 0.83 m. In the Providence River, water clarity generally decreased along a north-to-south gradient.
R/V Monitor's Blog
On Wednesday, July 15th, the crew of the R/V Monitor was out on the upper Bay collecting nutrients samples, taking Secchi Disk water clarity measurements, conducting water column profiles using a profiler sonde, and conducting real-time surface mapping of water quality parameters, including dissolved oxygen, chlorophyll, water temperature, salinity, and pH, all in an effort to document water quality improvements associated with NBC construction projects. Sara captained the boat while monitoring professionals Mike and Amanda collected the samples and data. It was a cloudy day with a northeast wind. There was no chop on the water. The photo below featuring sailors enjoying the day was taken at Edgewood Yacht Club.
Data were collected on July 15, 2020 while the R/V Monitor was underway collecting nutrient samples in the Providence and Seekonk River estuaries. The chlorophyll concentrations were variable and mostly good to fair with poor concentrations in the Seekonk River. From north to south, average chlorophyll concentrations were as follows: Seekonk River (62.09 µg/L), Upper Providence River (8.10 µg/L), Edgewood Shoals area (8.43 µg/L), Pawtuxet River area (6.86 µg/L ), and Lower Providence River area (10.37 µg/L ). Overall, chlorophyll ranged between 1.80 and 203.50 µg/L with an overall average of 22.74 µg/L. The chlorophyll data from this date are presented in the map below:
The geometric mean of fecal coliform results for all sites was 30 MPN/100 mL; counts were higher at the Seekonk River sites than the Providence River sites (geometric means of 153 MPN/100 mL and 14 MPN/100 mL, respectively). The maximum count (2,300 MPN/100 mL) was measured at Point St. Bridge. Results from the Providence River were within the state standards for primary contact, however, results from the Seekonk River exceeded these state standards. Results from both rivers exceeded state shellfishing criteria.
The enterococci results increased slightly from the previous sampling event on June 24, from an overall geomean of 10 MPN/100 mL to 16 MPN/100 mL. Enterococci results ranged from <10 MPN/100 mL measured at four sites (Phillipsdale Landing, South FP East, Gaspee Point, and Conimicut Point) to 323 MPN/100 mL at Point St. Bridge. These enterococci results were within the primary contact geometric mean criterion of 35 MPN/100 mL for the Seekonk and Providence Rivers, however the single sample maximum criterion of 104 MPN/100 mL was exceeded.
Please note: the results of NBC's fecal coliform and enterococci monitoring are for informational/research purposes only and are not intended to suggest official state compliance with bathing or shellfishing standards.
Water Column Clarity
Water clarity was measured at six locations in the Providence and Seekonk Rivers on July 8, 2020. Conditions were relatively dry in the few days leading up to the survey, with only 0.03 inches of precipitation recorded on the day of sampling. Average Secchi depth increased by 0.08 m since the previous survey, from 1.69 m to 1.77 m. Bullock Reach was the only site that exhibited decreased clarity (-0.20 m) since the last survey. The greatest increase in clarity was observed at India Point Park, where clarity increased by 0.33 m, from 1.57 m to 1.90 m. India Point Park and Point Street Bridge had the greatest water clarity, at 1.90 m, while Phillipsdale Landing had the lowest water clarity, at 1.57 m. Water clarity was variable throughout the Bay, with no clear north-to-south gradient, but overall, water clarity demonstrated an improvement from the last survey.