Historical News

Week of September 26 - October 2, 2021

Fixed Site Network

Phillipsdale Landing

Water quality at Phillipsdale Landing was fair-to-poor this week. Rainfall was moderate and Blackstone River flows remained elevated above historical means. Specifically, 0.35 inches of rainfall were recorded on September 26th and 0.16 inches recorded on September 28th at TF Green. Salinity at the surface decreased compared to the week before, averaging 6.8 ppt and ranging 2.1-11.8 ppt. Bottom salinity increased, averaging 22.5 ppt and ranging 6.9-30.7 ppt. Water temperatures cooled slightly, averaging 19.6°C on the surface and 21.3°C on the bottom. Surface temperatures ranged from 15.9°C to 22.8°C while bottom temperatures ranged from 18.3°C to 22.4°C.

Surface dissolved oxygen (DO) averaged 6.9 mg/L, with a minimum of 4.1 mg/L. Bottom DO averaged 3.1 mg/L, with a minimum of 1.1 mg/L. Hypoxic conditions (DO ≤ 2.9 mg/L) at the bottom increased this week, with the longest duration hypoxic period (10 hours) occurring on September 28th. Generally, DO conditions were better at low tide and hypoxic conditions were associated with the high-salinity flows of the rising and high tide. Chlorophyll concentrations decreased this week, averaging 5.0 ug/L on the surface and 4.2 ug/L on the bottom, with a surface maximum of 15.4 ug/L. Please note that tidal fluctuations and Blackstone River flow greatly influence water column salinity, temperature, and DO at this location.

Bullock Reach

Sondes were swapped for routine maintenance on the morning of September 29th. Water quality at Bullock Reach was fair this week. Salinity at the surface averaged 26.7 ppt and ranged from 21.6 ppt to 29.8 ppt. Salinity at the mid depth averaged 29.3 ppt and ranged from 24.9 ppt to 33.1 ppt. Salinity in bottom waters averaged 31.8 ppt and ranged from 28.6 ppt to 34.4 ppt. Temperatures cooled since the previous week, averaging 20.7°C, 21.1°C, and 21.1°C at the surface, mid, and bottom, respectively. Surface temperatures ranged from 18.4°C to 22.9°C, mid temperatures ranged from 19.4°C to 22.4°C, and bottom temperatures ranged from 19.8°C to 22.0°C.

DO concentrations were similar to the previous week, averaging 6.5 mg/L at the surface, 5.5 mg/L at mid-depth, and 4.9 mg/L at the bottom. Waters at all depths remained above the hypoxia threshold, with minimum bottom DO measuring 3.7 mg/L. Chlorophyll concentrations averaged 5.1 ug/L at the surface and 4.6 ug/L at mid-depth; please note that approximately 10 hours of mid-depth chlorophyll data from September 29th were omitted from this summary due to a suspect increase which may have been associated with sonde fouling observed at instrument retrieval. Evidence of phytoplankton bloom activity was greatest during the first half of the week. The maximum chlorophyll value in surface waters was 16.3 ug/L, on September 28th.

Week of September 19 - 25, 2021

Fixed Site Network

Phillipsdale Landing

Water quality at Phillipsdale Landing was fair-to-poor this week. Rainfall was light to moderate, and Blackstone River flows remained elevated above historical means. Specifically, 0.13 inches of rain were recorded on September 24th and trace amounts recorded on several other days at TF Green. Salinity at the surface increased compared to the week before, averaging 11.4 ppt and ranging 1.6-21.7 ppt. Bottom salinity averaged 20.9 ppt and ranged 3.5-28.1 ppt. Water temperatures averaged 21.9°C on the surface and bottom for the second week in a row. Surface temperatures ranged from 19.2°C to 23.2°C while bottom temperatures ranged from 21.1°C to 22.6°C.

Surface dissolved oxygen (DO) averaged 5.9 mg/L, with a minimum of 3.1 mg/L. Bottom DO averaged 3.6 mg/L, with a minimum of 2.1 mg/L. Hypoxic conditions (DO ≤ 2.9 mg/L) at the bottom were most extensive early in the week. The longest duration hypoxic period this week was just over 8 hours on September 19th. There was improvement in bottom DO as the week progressed. Chlorophyll concentrations increased slightly this week, averaging 8.1 ug/L on the surface and 7.0 ug/L on the bottom, with a surface maximum of 27.3 ug/L. Please note that tidal fluctuations and Blackstone River flow greatly influence water column salinity, temperature, and DO at this location.

Bullock Reach

Water quality at Bullock Reach was fair this week. Salinity at the surface averaged 26.1 ppt and ranged from 21.2 ppt to 28.3 ppt. Salinity at the mid depth averaged 28.0 ppt and ranged from 25.7 ppt to 30.4 ppt. Salinity in bottom waters averaged 29.5 ppt and ranged from 27.3 ppt to 31.5 ppt. Temperatures were similar to the previous week, averaging 22.0°C, 21.7°C, and 21.3°C at the surface, mid, and bottom, respectively. Surface temperatures ranged from 20.9°C to 22.8°C, mid temperatures ranged from 20.7°C to 22.4°C, and bottom temperatures ranged from 20.3°C to 22.4°C.

DO concentrations were also similar to the previous week, averaging 6.9 mg/L at the surface, 6.0 mg/L at mid-depth, and 4.9 mg/L at the bottom. Waters at all depths remained above the hypoxia threshold, with minimum bottom DO measuring 3.4 mg/L. Chlorophyll concentrations averaged 9.0 ug/L at the surface and 5.3 ug/L at mid-depth. Evidence of phytoplankton bloom activity was greatest during the first half of the week. The maximum chlorophyll value in surface waters was 36.4 ug/L, on September 21st.

Week of September 05 – 11, 2021

Nutrients Sampling

​Nutrient samples were collected from seven local river stations and three bay stations on September 8, 2021; the Bay stations were all sampled at the surface and bottom. Please note that due to mechanical issues with the NBC research vessel, R/V Monitor, there was limited Bay nutrient sampling this week. Weather conditions leading up to the sampling day were mostly dry, with 0.02 inches of recorded rainfall in the five days prior to sampling.

Among the river stations sampled, the highest total nitrogen (TN), total dissolved nitrogen (TDN), and dissolved inorganic nitrogen (DIN) were all observed at Moshassuck River at Mill Street. At this site, the average of two duplicates for TN, TDN, and DIN concentrations were 930 ppb, 879.5 ppb, and 764.1 ppb, respectively. The lowest TN (644 ppb) and DIN (376.7 ppb) were observed at Blackstone River at Slater Mill, while the lowest TDN( 639 ppb) was observed Blackstone River at Stateline.

Among the Bay stations sampled, the highest surface TN (778 ppb) and DIN (428.1 ppb) were observed at Phillipsdale Landing, while the highest TDN (812.5 ppb; average of two duplicates) was observed at Edgewood Shoal. The lowest surface TN (699 ppb) and TDN (662 ppb) were observed at Edgewood Yacht Club, while the lowest DIN (311.5 ppb; average of two duplicates) was observed at Edgewood Shoal. Chlorophyll a concentrations at the Bay sites decreased since the previous sampling event, averaging 2.54 ug/L across all sites. The maximum result of 3.09 ug/L occurred at Edgewood Shoal (average of two duplicates).   

Results from nutrient sampling on September 14 are pending analysis. The next scheduled sample date is September 22. ​

Week of June 27 – July 03, 2021

Water Column Profiles

​Water column profiles were at six locations in the Providence River using a Seabird profiling instrument on July 30, 2021. Conditions leading up to sampling were dry with no rainfall recorded at T.F. Green. Evidence of density stratification was observed at two locations: Conimicut Point and Edgewood Yacht Club.

Surface salinities among all sites ranged from 19.3 PSU at India Point Park to 24.1 PSU at Conimicut Point. Bottom salinities ranged from 23.6 PSU at Pawtuxet Cove. The warmest water temperatures were observed at Pawtuxet Cove, ranging from 26.2°C at the surface to 24.6°C at the bottom. The lowest surface temperatures (25.3°C) were observed at Conimicut Point, while the lowest bottom temperatures (18.9°C) were observed at India Point Park.

This week, hypoxic conditions (dissolved oxygen (DO) concentrations <2.9 mg/L) were observed in the bottom waters at India Point Park. Across all sites, DO ranged from 2.3 mg/L in bottom waters at India Point Park to 12.9 mg/L at the surface at Edgewood Yacht Club. Please note that due to quality control issue, numerical fluorescence data are not posted at this time.​


Week of September 12 - 18, 2021

Fixed Site Network

Phillipsdale Landing

Water quality at Phillipsdale Landing was fair-to-poor this week. Sondes were swapped out for routine maintenance mid-day on September 14th. Blackstone River flows remained elevated above historical mean flows, though generally declined over the course of the week. Rainfall was light to moderate, just 0.8 inches on September 16th as measured at TF Green. Salinity at the surface increased compared to the week before, averaging 6.0 ppt and ranging 1.8-18.3 ppt. Bottom salinity averaged 17.8 ppt and ranged 3.3-28.3 ppt. Water temperatures averaged 21.9°C on the surface and bottom. Surface temperatures ranged from 20.0°C to 23.8°C while bottom temperatures ranged from 20.5°C to 23.4°C.

Surface dissolved oxygen (DO) averaged 6.7 mg/L, with a minimum of 2.8 mg/L. Hypoxic conditions (DO ≤ 2.9 mg/L) at the surface consisted of an isolated single reading on September 18th. Bottom DO was hypoxic approximately half of the week, coincident with high tides. The average bottom DO was 3.4 mg/L, with a minimum of 1.8 mg/L and maximum of 7.5 mg/L. Hypoxic conditions persisted for up to 10 hours at a time. Chlorophyll concentrations remained low this week, averaging 3.6 ug/L on the surface and 3.4 ug/L on the bottom, with a surface maximum of 9.7 ug/L. Please note that tidal fluctuations and Blackstone River flow greatly influence water column salinity, temperature, and DO at this location.

Bullock Reach

Sondes were swapped out for maintenance on the morning of September 14th. The retrieved sondes had been deployed for three weeks, compared to the routine two-weeks, with the delay due to the NBC's research vessel being out of service. Water quality at Bullock Reach was fair this week. Salinity at the surface averaged 22.6 ppt and ranged from 18.3 ppt to 26.0 ppt. Salinity at the mid depth averaged 26.7 ppt and ranged from 22.9 ppt to 30.2 ppt. Salinity in bottom waters averaged 29.3 ppt and ranged from 26.1 ppt to 31.6 ppt. Temperatures were similar to the previous week, averaging 22.3°C, 21.9°C, and 21.2°C at the surface, mid, and bottom, respectively. Surface temperatures ranged from 21.3°C to 23.3°C, mid temperatures ranged from 20.7°C to 23.2°C, and bottom temperatures ranged from 20.2°C to 22.5°C.

DO concentrations were also similar to the previous week, averaging 6.9 mg/L at the surface, 5.5 mg/L at mid-depth, and 4.0 mg/L at the bottom. Waters at all depths remained above the hypoxia threshold, with minimum bottom DO measuring 3.1 mg/L. Chlorophyll concentrations averaged 18.6 ug/L at the surface and 7.9 ug/L at mid-depth. Concentrations were highest in the first half of the week, with the bloom activities from the prior week beginning to dissipate around Tuesday. The maximum chlorophyll value in surface waters was 88.2 ug/L, on September 13th.

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