News – Page 7 – Narrabay

September 23 – 29, 2024

Phillipsdale Landing

Overall, water quality at Phillipsdale Landing was good to fair this week. Weather conditions included a rain event, with 1.06 inches of precipitation recorded at T.F. Green. The Blackstone River flow fluctuated through the week in response to rain, though it remained below the 20-year daily median through the week. Surface salinity averaged 23.7 ppt and ranged from 16.3 ppt to 27.8 ppt. At the bottom, salinity averaged 27.6 ppt and ranged from 24.6 ppt to 29.7 ppt. Temperatures continued to decline this week, averaging 19.4°C at the surface and ranging 17.9°C – 21.0°C. At the bottom, temperatures averaged 19.5°C and ranged 18.9°C – 20.2°C.

Dissolved oxygen (DO) at Phillipsdale Landing remained above the hypoxia threshold (i.e., DO >2.9 mg/L) at the surface throughout the week, while DO at the bottom waters dropped below the hypoxic threshold throughout the week. Surface DO averaged 6.16 mg/L and ranged from 3.77 mg/L to 8.88 mg/L. Bottom DO concentrations averaged 4.3 mg/L and ranged from 2.2 mg/L to 5.7 mg/L. The longest period of hypoxic conditions (1 hour) occurred at the bottom depth on the afternoon of September 26^th. During this period, bottom DO averaged around 2.51 mg/L. Chlorophyll readings decreased from last week, averaging 15.1 µg/L at the surface and 6.0 µg/L at the bottom. Maximum chlorophyll at the surface reached 59.98 µg/L on the afternoon of September 29^th. Please note that tidal fluctuations and Blackstone River flows greatly influence water column salinity, temperature, and DO at this location.

Bullock Reach

Sondes were swapped this week on the morning of September 24^th. Overall, the water quality was good at Bullock Reach this week. Salinity averaged 28.8 ppt, 30.2 ppt, and 31.8 ppt at the surface, middle, and bottom sondes, respectively. Surface salinity ranged 26.5 – 30.1 ppt, mid salinity ranged 28.7 – 31.4 ppt, and bottom salinity ranged 29.8 – 32.3 ppt. Surface temperature averaged 19.1°C and ranged from 18.1°C to 20.8°C. Mid temperatures averaged 19.0°C and ranged from 18.5°C to 20.2°C. Bottom temperatures averaged 18.8°C and ranged from 18.7°C to 19.2°C.

DO at Bullock Reach remained above the hypoxia threshold (i.e., DO >2.9 mg/L) throughout the week. Surface DO averaged 7.2 mg/L and ranged 6.2 – 8.7 mg/L. In the mid waters, DO averaged 6.6 mg/L and ranged 5.7 – 7.7 mg/L. At the bottom, DO averaged 6.1 mg/L and ranged 5.4 – 6.9 mg/L. Chlorophyll readings ranged from low to elevated, with evidence of moderate phytoplankton blooms occurring throughout the week. Readings averaged 9.2 µg/L at the surface, 7.5 µg/L at mid-depth, and 2.6 µg/L at the bottom. The maximum surface chlorophyll was 21.2 µg/L on the evening of September 25^th.

July 16, 2025

On July 16th, 2025, seventeen 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, 0.01 inches of precipitation was recorded at TF Green. Overall bacteria counts were lower than during the previous sampling event.

Fecal coliform counts were higher in the Seekonk River, compared to the Providence River (geometric mean of 82 MPN/100 mL for the Seekonk River compared to 16 MPN/100mL for the Providence River) for sampling conducted on July 16th. The maximum count (430 MPN/100 mL) was measured at the India Point Park sampling location.

Fecal coliform counts were lower in the Providence River, compared to the previous sampling on July 2nd (geometric mean of 16 MPN/100 mL compared to 49 MPN/100 mL on 7/2). Fecal coliform counts were lower in the Seekonk River, compared to the previous sampling on July 2nd (geometric mean of 82 MPN/100 mL compared to 4916 MPN/100 mL on 7/2).

Enterococci results had an overall geometric mean of 11 MPN/100 mL. Enterococci counts ranged from <10 MPN/100 mL at most sites to 20 MPN/100 mL at Point St Bridge.

The next scheduled sampling date is July 30th.

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.

July 16, 2025

Water clarity was measured at seven locations in the Providence River and Seekonk River estuaries on July 16, 2025. In the five days prior to the survey, 0.01 inches of precipitation were recorded at TF Green. Secchi depth averaged 1.9 meters. The lowest clarity this week (1.5 meters) was measured at India Point Park, while the greatest clarity (2.5 meters) was measured at Point Street Bridge. There was no clear north-to-south gradient in water clarity among the sites this week. Overall, water clarity at most locations remained relatively consistent compared to previous measurements (data collected July 8, 2025). However, water quality at Phillipsdale Landing increased (0.8 meters) and water quality at Conimicut Point decreased (1.6 meters), both compared to previous measurements (data collected July 8, 2025).

June 11, 2025

Nutrient samples were collected from seven river stations and seven bay stations on June 11^th. All bay stations were sampled at the surface and bottom. In the five days prior to sampling, there were 0.85 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) were observed at Pawtuxet River at Broad St. (TN = 1,090 ppb, TDN = 1,200 ppb, DIN = 863.7). The lowest TN and DIN were observed at Woonasquatucket River at Manton Ave. Bridge (TN = 638 ppb, DIN = 406.4 ppb, average of duplicates). The lowest TDN was observed Moshassuck River @ Footbridge at Mill St. (660 ppb).

Among the bay stations sampled, the highest surface TN was observed at Phillipsdale Landing (1,080 ppb). The highest TDN and DIN were observed at Pawtuxet Cove (TDN = 963 ppb, DIN = 654.7 ppb). The lowest surface TN, TDN, and DIN were observed at Edgewood Shoal (TN = 597 ppb, TDN = 176 ppb, DIN = 13 ppb, reflecting minimum detection limits for DIN)

The next scheduled sampling date is June 25^th, 2025.

July 8, 2025

Water column profiles were conducted at eight locations in the Providence and Seekonk River estuaries on July 8, 2025 using a Seabird Electronics profiler. In the five days leading up to the survey, 0.55 inches of precipitation were recorded at T.F. Green. Water column stratification varied between the sites this week from well-mixed at Pawtuxet Cove to moderately stratified at Pomham Rocks, India Point Park and Phillipsdale Landing.

Dissolved oxygen (DO) conditions were below the hypoxia threshold (2.9 mg/L) in the lower portion of the water column at India Point Park, Pomham Rocks, Bullock Reach Buoy, Edgewood Yacht Club, and Edgewood Shoal, and in the middle and lower portion of the water column at Phillipsdale Landing. The highest fluorescence readings for the week were measured around 1 meter below the surface at Phillipsdale Landing.

July 2, 2025

Water column profiles were conducted at eight locations in the Providence and Seekonk River estuaries on July 2, 2025 using a Seabird Electronics profiler. In the five days leading up to the survey, 0.02 inches of precipitation were recorded at T.F. Green. Water column stratification varied between the sites this week from well-mixed at Point Street Bridge and Pawtuxet Cove to moderately stratified at India Point Park and Phillipsdale Landing.

Dissolved oxygen (DO) conditions were below the hypoxia threshold (2.9 mg/L) in the middle and lower portion of the water column at Edgewood Yacht Club and India Point Park, and in all portions (upper, middle, and lower) of the water column at Point Street Bridge and Phillipsdale Landing. The highest fluorescence readings for the week were measured around 1 meter below the surface at Pawtuxet Cove.

July 2, 2025

On July 2nd, 2025, 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, 0.03 inches of precipitation was recorded at TF Green. Overall bacteria counts were higher than during the previous sampling event.

Fecal coliform counts were higher in the Seekonk River, compared to the Providence River (geometric mean of 4916 MPN/100 mL for the Seekonk River compared to 49 MPN/100mL for the Providence River) for sampling conducted on July 2nd. The maximum count (240,000 MPN/100 mL) was measured at the Point St. Bridge sampling location.

Fecal coliform counts were higher in the Providence River, compared to the previous sampling on June 4th (geometric mean of 49 MPN/100 mL compared to 30 MPN/100 mL on 6/4). Fecal coliform counts were higher in the Seekonk River, compared to the previous sampling on June 4th (geometric mean of 4916 MPN/100 mL compared to 93 MPN/100 mL on 6/4).

Enterococci results had an overall geometric mean of 333 MPN/100 mL. Enterococci counts ranged from <10 MPN/100 mL at Conimicut Point and Gaspee Point to 6488 MPN/100 mL at Point St Bridge.

The next scheduled sampling date is July 16th.

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.

July 8, 2025

Water clarity was measured at eight locations in the Providence River and Seekonk River estuaries on July 8, 2025. In the five days prior to the survey, 0.55 inches of precipitation were recorded at TF Green. Secchi depth averaged 2.3 meters. The lowest clarity this week (1.3 meters) was measured at Phillipsdale Landing, while the greatest clarity (3.7 meters) was measured at Conimicut Point. There was a general north-to-south trend of increasing water clarity among the sites this week. Overall, water clarity remained approximately the same from the previous measurements (data collected July 2, 2025).

July 2, 2025

Water clarity was measured at eight locations in the Providence River and Seekonk River estuaries on July 2, 2025. In the five days prior to the survey, 0.02 inches of precipitation were recorded at TF Green. Secchi depth averaged 2.2 meters. The lowest clarity this week (1.4 meters) was measured at Phillipsdale Landing, while the greatest clarity (2.9 meters) was measured at Conimicut Point. There was a general north-to-south trend of increasing water clarity among the sites this week. Overall, water clarity remained approximately the same from the previous measurements (data collected June 25, 2025).

May 28, 2025

Nutrient samples were collected from fourteen river stations and eight bay stations on May 28^th. All bay stations were sampled at the surface and one station (Edgewood Shoal) was sampled at the bottom. In the five days prior to sampling, 0.06 inches of precipitation were recorded at T.F. Green.

Among the river stations sampled, the highest total nitrogen (TN), total dissolved nitrogen (TDN), and dissolved inorganic nitrogen (DIN) were observed Ten Mile River @ Central Ave. (TN = 1,050 ppb, TDN = 1,100 ppb, DIN = 757). The lowest TN, and TDN were observed at Moshassuck River @ Higginson Ave. (TN = 458 ppb, TDN = 552 ppb). The lowest DIN was observed at Coles River @ Milford Rd. (DIN = 116 ppb).

Among the bay stations sampled, the highest surface total nitrogen (TN) was observed at Phillipsdale Landing (TN = 870 ppb). The highest total dissolved nitrogen (TDN), and dissolved inorganic nitrogen (DIN) were observed at Pawtuxet Cove (TDN = 771 ppb, DIN = 568 ppb). The lowest surface TN was observed at the Bullock Reach Buoy (TN = 584). The lowest surface TDN and DIN concentrations were observed at Conimicut Point (TDN = 214 ppb, DIN = 72 ppb).

The next scheduled sampling date is June 11, 2025.