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 26th. 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 29th. 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 24th. 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 25th.