Phillipsdale Landing
Sondes were swapped this week on the morning of September 9th. Overall, the water quality at Phillipsdale Landing was fair this week. Weather conditions were dry, with no precipitation recorded at T.F. Green. The Blackstone River flow fluctuated throughout the week, rising above the 20-year daily median. Surface salinity averaged 22.6 ppt and ranged from 15.1 ppt to 27.2 ppt. Bottom salinity averaged 25.9 ppt and ranged from 15.0 ppt to 29.5 ppt. Temperatures averaged 22.0°C at the surface and 22.2°C at the bottom. Surface temperatures ranged from 20.1°C to 24.2°C, while bottom temperatures ranged from 21.1°C to 23.2°C.
Dissolved oxygen (DO) at Phillipsdale Landing dropped below the hypoxia threshold (i.e., DO >2.9 mg/L) briefly at the start of the week. The longest periods of hypoxic conditions spanned 2.25 hours, occurring during the morning of September 8th. During this period, the bottom DO averaged around 2.53 mg/L. Surface DO averaged 6.0 mg/L and ranged from 2.6 mg/L to 14.4 mg/L. Bottom DO concentrations averaged 4.3 mg/L and ranged from 2.3 mg/L to 9.3 mg/L. Chlorophyll readings decreased from last week, averaging 7.8 µg/L at the surface and 5.3 µg/L at the bottom. Maximum chlorophyll at the surface reached 60.8 µg/L on the afternoon of September 14th. Please note that tidal fluctuations and Blackstone River flows greatly influence water column salinity, temperature, and DO at this location.
Bullock Reach
Overall, water quality was good at Bullock Reach this week. Salinity averaged 28.9 ppt, 30.3 ppt, and 31.7 ppt at the surface, middle, and bottom sondes, respectively. Surface salinity ranged 27.3– 30.3 ppt, middle salinity ranged 28.3-31.4 ppt, and bottom salinity ranged 29.9 – 32.6 ppt. Surface temperature averaged 21.5°C and ranged from 20.5°C to 22.6°C. Middle temperatures averaged 21.4°C and ranged from 20.7°C to 22.8°C. Bottom temperatures averaged 21.2°C and ranged from 20.7°C to 22.5°C.
Dissolved oxygen (DO) at Bullock Reach remained above the hypoxia threshold (i.e., DO >2.9 mg/L) throughout the week. Surface DO averaged 6.8 mg/L and ranged 5.1 – 8.8 mg/L. Middle DO averaged 6.3 mg/L and ranged 4.9 – 8.5 mg/L. At the bottom, DO averaged 5.6 mg/L and ranged 4.6 – 7.4 mg/L. Chlorophyll readings ranged from low to elevated throughout the week. Readings averaged 12.2 µg/L at the surface, 9.2 µg/L at the middle, and 3.76 µg/L at the bottom. The maximum surface chlorophyll was 27.9 µg/L on the afternoon of September 9th.