Phillipsdale Landing
Sondes were swapped this week on the morning of September 23rd. Overall, the water quality at Phillipsdale Landing was fair this week Weather conditions included frequent rain events this week, with 4.33 inches of precipitation recorded at T.F. Green. The Blackstone River flow fluctuated throughout the week. Surface salinity averaged 19.8 ppt and ranged from 9.2 ppt to 26.4 ppt. At the bottom, salinity averaged 24.6 ppt and ranged from 15.1 ppt to 28.5 ppt. Temperatures averaged 22.0°C at the surface and 21.8°C at the bottom. Surface temperatures ranged from 20.2°C to 23.8°C, while bottom temperatures ranged from 21.2°C to 22.7°C.
Dissolved oxygen (DO) at Phillipsdale Landing dropped below the hypoxia threshold (i.e., DO >2.9 mg/L) throughout the week. The longest periods of hypoxic conditions spanned 18.25 hours, occurring during the night of September 27th to the afternoon of September 28th. During this period, the bottom DO averaged around 2.13 mg/L. Surface DO averaged 5.3 mg/L and ranged from 2.4 mg/L to 9.9 mg/L. Bottom DO concentrations averaged 3.5 mg/L and ranged from 1.3 mg/L to 8.7 mg/L. Chlorophyll readings averaged 8.0 µg/L at the surface and 9.3 µg/L at the bottom. Maximum chlorophyll at the surface reached 42.9 µg/L on the morning of September 24th. 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 28.1 ppt, 31.5 ppt, and 32.1 ppt at the surface, middle, and bottom sondes, respectively. Surface salinity ranged 25.0 – 30.4 ppt, middle salinity range 28.9 – 32.5 ppt, and bottom salinity ranged 31.1 – 32.7 ppt. Surface temperature averaged 21.3°C and ranged from 20.2°C to 22.8°C. Middle temperature averaged 21.0°C and ranged from 20.3°C to 21.7°C. Bottom temperatures averaged 20.8°C and ranged from 20.4°C to 21.2°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 4.8 – 10.1 mg/L. Middle DO averaged 5.9 mg/L and ranged 4.1 – 8.5 mg/L. At the bottom, DO averaged 5.5 mg/L and ranged 4.3 – 6.5 mg/L. Chlorophyll readings ranged from low to elevated throughout the week. Readings averaged 6.6 µg/L at the surface, 10.4 µg/L at the middle, and 6.4 µg/L at the bottom. The maximum surface chlorophyll was 21.9 µg/L on the afternoon of September 28th.