News – Page 16 – Narrabay

December 10-16, 2023

Water clarity was measured at eight locations in the Providence River and Seekonk River estuaries on December 13th, 2023. Rainfall totaling 2.29 inches was recorded at TF Green in the five days prior to the survey. Secchi depth averaged 1.3 meters, compared to 4.5 meters on the previous survey (November 30th). The lowest clarity this week (0.7 meters) was measured at Phillipsdale Landing, while the greatest clarity (1.9 meters) was measured at Conimicut Point. There was a general north-to-south gradient of increasing water clarity among the sites this week.

Week of December 11 – 17, 2023

Nutrient samples were collected from 11 river stations and 8 bay stations on December 13th. Edgewood Shoal was sampled at the surface and bottom; all other bay stations were sampled at the surface only. In the five days prior to sampling, there were 0.64 inches of precipitation on December 10th and 1.65 inches on December 11th recorded at T.F. Green.

Among the river stations sampled, the highest total nitrogen (TN) and total dissolved nitrogen (TDN) concentrations were observed at Warren Reservoir/Kickemuit River (TN = 849 ppb, TDN = 825 ppb); the highest dissolved inorganic nitrogen (DIN) was at Moshassuck River @ Footbridge at Mill St. (439 ppb). The lowest TN was at Pawtuxet River @ Broad St. (551 ppb), the lowest TDN was at Coles River @ Milford Rd (505 ppb), and the lowest DIN was at Palmer River @ Rt. 6 (115 ppb).

Among the bay stations sampled, the highest surface TN and TDN were observed at India Point Park (TN = 920 ppb, TDN = 742 ppb); the highest surface DIN was observed at Pomham Rocks (596 ppb). The lowest surface TN and DIN were observed at Pawtuxet Cove (TN = 614 ppb, DIN = 380 ppb), while the lowest surface TDN was at Conimicut Point (524 ppb). Chlorophyll a concentrations at the surface bay stations were low this week; concentrations averaged 0.311 μg/L overall with a maximum of 0.589 μg/L at Phillipsdale Landing.

The next scheduled sampling date is December 27, 2023.

December 3 – 9, 2023

On the morning of December 4th, the Phillipsdale Landing sondes were successfully removed for the 2023 season! For the one day of data available this week, water quality remained good, with similar conditions to last week.

The sondes at Bullock Reach were retrieved on November 14th for the 2023 season.

November 26 – December 2, 2023

Phillipsdale Landing

Overall, water quality was good at Phillipsdale Landing this week. There were 0.74 inches of precipitation recorded at T.F. Green this week, and Blackstone flows continued to be higher than normal for this time of year. Surface salinity averaged 8.0 ppt and ranged from 3.2 ppt to 20.4 ppt. Bottom salinity averaged 19.8 ppt and ranged from 6.2 ppt to 27.2 ppt. Temperatures continued to decline, averaging 6.4°C at the surface and ranging from 3.6°C to 8.8°C. At the bottom, temperatures averaged 8.5°C and ranged from 5.5°C to 10.1°C.

Dissolved oxygen (DO) at Phillipsdale Landing remained above the hypoxia threshold of 2.9 mg/L at both the surface and bottom all week. Surface DO was similar to last week, averaging 10.9 mg/L and ranging from 8.8 to 12.4 mg/L. Bottom DO averaged 8.7 mg/L and ranged from 7.3 mg/L to 11.0 mg/L. Chlorophyll readings remained mostly low with a few slightly elevated readings at the bottom. Chlorophyll averaged 0.6 ug/L at the surface and 1.9 ug/L at the bottom. Please note that tidal fluctuations and Blackstone River flows greatly influence water column salinity, temperature, and DO at this location.

Bullock Reach

The sondes at Bullock Reach have been retrieved for the 2023 season.

Week of November 27 – December 3, 2023

Nutrient samples were collected from 7 river stations on November 29th and 7 bay stations on November 30th. All bay stations were sampled at the surface and bottom. In the five days prior to sampling, there were 0.69 inches of precipitation recorded at T.F. Green.

Among the river stations sampled, the highest total nitrogen (TN), total dissolved nitrogen (TDN), and dissolved inorganic nitrogen (DIN) concentrations were observed at Blackstone River @ Bikepath Bridge (TN = 972 ppb, TDN = 965 ppb, DIN = 782 ppb, average of duplicates). The lowest TN, TDN, and DIN were observed at Moshassuck River @ Higginsin Ave (TN = 519 ppb, TDN = 503 ppb, DIN = 362 ppb).

Among the bay stations sampled, the highest surface TN, TDN, and DIN were observed at Phillipsdale Landing (TN = 1,200 ppb, TDN = 1,020 ppb, DIN = 850 ppb). The lowest surface TN, TDN, and DIN were observed at Bullock Reach Buoy (TN = 524 ppb, TDN = 413 ppb, DIN = 221 ppb). Chlorophyll a concentrations at the surface bay stations were low this week; concentrations averaged 0.63 μg/L overall with a maximum of 1.15 μg/L at Bullock Reach Buoy.

The next scheduled sampling date is December 13, 2023.

March 27, 2024

On March 27th, twenty stations were sampled for fecal coliform bacteria in the Providence and Seekonk Rivers; five of these stations were also sampled for enterococci bacteria. In the five days prior to sampling, precipitation totaled 3.12 inches as recorded at TF Green. Overall, bacteria counts were higher in both the Seekonk and Providence Rivers this week than during the previous sampling event on March 13th, likely because this event had less time in between the rainfall and sampling.

Fecal coliform counts were slightly lower in the Seekonk River sites than in the Providence River sites (geometric means of 51 MPN/100 mL and 66 MPN/100 mL, respectively). The maximum count (430 MPN/100 mL) was measured at both Collier Point Park and Off FP Outfall.

Enterococci results had an overall geometric mean of 26 MPN/100 mL. Enterococci counts ranged from 20 MPN/100 mL at South FP East to 41 MPN/100 mL at both Phillipsdale Landing and Gaspee Point.

The table below lists the Rhode Island bacteria standards for primary contact and shellfishing established by the Rhode Island Department of Environmental Management (RIDEM). RIDEM defines primary contact as any recreational activities in which there is prolonged and intimate contact with water, involving considerable risk of ingesting water (e.g., swimming, diving, water skiing and surfing). Please note that the RIDEM bacteria standards are provided here for informational purposes only and are not intended to indicate official state compliance with primary contact or shellfishing standards.

Summary of Rhode Island Bacteria Standards for Saltwater Primary Contact and Shellfishing

	Fecal Coliform	Enterococci
Primary Contact¹	Geometric mean ≤50 MPN/100 mL <10% of samples >400 MPN/100 mL	Geometric mean ≤35 colonies/100 mL All samples ≤104 colonies/100 mL²
Shellfishing	Geometric mean ≤14 MPN/100 mL <10% of samples >49 MPN/100 mL³	NO ENTEROCOCCI CRITERIA

¹Fecal coliform primary contact criteria applied only when adequate enterococci data are not available; ²Single sample maximum criterion for determining beach swimming advisories at designated beaches as evaluated by the Rhode Island Department of Health; ³For a three-tube decimal dilution

Table adapted from Rhode Island Water Quality Regulations (250-RICR-150-05-1); see regulations for complete details.

March 13, 2024

On March 13th, twenty stations were sampled for fecal coliform bacteria in the Providence River and Seekonk River; five of these stations were also sampled for enterococci bacteria. In the five days prior to sampling, precipitation totaled 2.32 inches as recorded at TF Green.

Fecal coliform counts were slightly lower in the Seekonk River sites than in the Providence River sites (geometric means of 29 MPN/100 mL and 33 MPN/100 mL, respectively). The maximum count (430 MPN/100 mL) was measured at Point Street Bridge.

Enterococci results had an overall geometric mean of 12 MPN/100 mL. Enterococci counts ranged from non-detect at most sites to a max of 31 MPN/100 mL at Point Street Bridge.

Summary of Rhode Island Bacteria Standards for Saltwater Primary Contact and Shellfishing

	Fecal Coliform	Enterococci
Primary Contact¹	Geometric mean ≤50 MPN/100 mL <10% of samples >400 MPN/100 mL	Geometric mean ≤35 colonies/100 mL All samples ≤104 colonies/100 mL²
Shellfishing	Geometric mean ≤14 MPN/100 mL <10% of samples >49 MPN/100 mL³	NO ENTEROCOCCI CRITERIA

Table adapted from Rhode Island Water Quality Regulations (250-RICR-150-05-1); see regulations for complete details.

November 19-25, 2023

Phillipsdale Landing

Overall, water quality was good at Phillipsdale Landing this week. There were 1.82 inches of precipitation recorded at T.F. Green this week, 1.71 of which occurred on 11/22. Blackstone flows were higher than historical averages all week, but particularly following the 11/22 rain event. Surface salinity averaged 8.8 ppt and ranged from 2.9 ppt to 20.7 ppt. Bottom salinity averaged 21.4 ppt and ranged from 6.5 ppt to 27.7 ppt. Temperatures continued to decline, averaging 8.1°C at the surface and ranging from 5.1°C to 10.5°C. At the bottom, temperatures averaged 10.4°C and ranged from 7.2°C to 12.4°C.

Dissolved oxygen (DO) at Phillipsdale Landing remained above the hypoxia threshold of 2.9 mg/L at both the surface and bottom all week. Surface DO was slightly higher than the previous week, averaging 10.2 mg/L and ranging from 8.3 to 11.8 mg/L. Bottom DO averaged 7.8 mg/L and ranged from 6.4 mg/L to 11.1 mg/L. Chlorophyll readings remained low, averaging 0.6 ug/L at the surface and 2.6 ug/L at the bottom. Please note that tidal fluctuations and Blackstone River flows greatly influence water column salinity, temperature, and DO at this location.

Bullock Reach

The sondes at Bullock Reach have been retrieved for the 2023 season.

November 19-25, 2023

On November 21, 2023, 15 stations were sampled for fecal coliform bacteria in the Providence and Seekonk Rivers; 3 of these stations were also sampled for enterococci bacteria. There was a smaller set of locations sampled than normal due to cold weather conditions and time constraints. In the five days prior to sampling, precipitation totaled 0.15 inches as recorded at TF Green.

Overall, bacteria levels were lower in both the Seekonk and Providence Rivers this week than during the previous sampling event on October 25th. Fecal coliform levels similar in the Seekonk River and Providence River sites (geometric means of 22 MPN/100 mL and 23 MPN/100 mL, respectively). The maximum concentration (230 MPN/100 mL) was measured at Point St Bridge.

Enterococci results had an overall geometric mean of 19 MPN/100 mL and ranged from <10 MPN/100 mL at Phillipsdale Landing and South FP East to 134 MPN/100 mL at Point St. Bridge.

Summary of Rhode Island Bacteria Standards for Saltwater Primary Contact and Shellfishing

	Fecal Coliform	Enterococci
Primary Contact¹	Geometric mean ≤50 MPN/100 mL <10% of samples >400 MPN/100 mL	Geometric mean ≤35 colonies/100 mL All samples ≤104 colonies/100 mL²
Shellfishing	Geometric mean ≤14 MPN/100 mL <10% of samples >49 MPN/100 mL³	NO ENTEROCOCCI CRITERIA

Table adapted from Rhode Island Water Quality Regulations (250-RICR-150-05-1); see regulations for complete details.

November 12-18, 2023

Phillipsdale Landing

Overall, water quality was good at Phillipsdale Landing this week. There were 0.16 inches of precipitation recorded at T.F. Green this week and Blackstone River flow was slightly higher than normal for this time of year. Surface salinity averaged 13.7 ppt and ranged from 3.7 ppt to 22.6 ppt. Bottom salinity averaged 22.9 ppt and ranged from 11.8 ppt to 28.3 ppt. Temperatures were slightly lower than last week, averaging 10.4°C at the surface and ranging from 7.9°C to 12.4°C. At the bottom, temperatures averaged 12.4°C and ranged from 10.5°C to 14.0°C.

Dissolved oxygen (DO) at Phillipsdale Landing remained above the hypoxia threshold of 2.9 mg/L at both the surface and bottom all week. Surface DO remained similar to the previous week, averaging 8.9 mg/L and ranging from 6.7 to 11.0 mg/L. Bottom DO averaged 6.8 mg/L and ranged from 5.4 mg/L to 8.8 mg/L. Chlorophyll readings remained low, averaging 0.6 ug/L at the surface and 1.3 ug/L at the bottom. Please note that tidal fluctuations and Blackstone River flows greatly influence water column salinity, temperature, and DO at this location.

Bullock Reach

The sondes at Bullock Reach were retrieved on the morning of November 14th for the 2023 season. For the two and half days of data this week before retrieval, water quality was good. Salinity averaged 25.7 ppt, 27.9 ppt, and 29.8 ppt at the surface, middle, and bottom sondes, respectively. Surface salinity ranged 23.5 – 27.9 ppt, mid salinity ranged 25.1 – 29.7 ppt, and bottom salinity ranged 29.0 – 30.4 ppt. Surface temperatures averaged 11.4°C and ranged from 10.2°C to 12.4°C. Mid temperatures averaged 12.4°C and ranged from 11.3°C to 13.2°C. Bottom temperatures averaged 13.2°C and ranged from 12.5°C to 13.7°C.

DO concentrations at Bullock Reach remained above the hypoxia threshold all week. Surface DO averaged 8.0 mg/L and ranged 7.4 – 8.8 mg/L. In the mid waters, DO averaged 7.5 mg/L and ranged 7.1 – 8.1 mg/L. At the bottom, DO averaged 7.1 mg/L and ranged 6.7 – 7.5 mg/L. Chlorophyll concentrations were low, averaging 1.2 ug/L, 1.9 ug/L, and 1.3 ug/L at the surface, mid, and bottom waters, respectively.

Phillipsdale Landing

Bullock Reach

Phillipsdale Landing

Bullock Reach

​Phillipsdale Landing

Bullock Reach

Phillipsdale Landing