Phillipsdale Landing
Overall, the water quality at Phillipsdale Landing was fair this week. Weather conditions included frequent rain events this week, with 1.59 inches of precipitation recorded at T.F. Green. The Blackstone River had a low flow throughout the week, remaining below the 20-year daily median throughout the week. Surface salinity averaged 21.3 ppt and ranged from 12.4 ppt to 25.9 ppt. At the bottom, salinity averaged 25.8 ppt and ranged from 17.9 ppt to 30.2 ppt. Temperatures averaged 23.1°C at the surface and 23.0°C at the bottom. Surface temperatures ranged from 20.9°C to 24.8°C, while bottom temperatures ranged from 21.8°C to 24.4°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 11 hours, occurring at the bottom depth from the night of September 2nd until September 3rd. During this period, the bottom DO averaged around 1.02 mg/L. Surface DO averaged 8.0 mg/L and ranged from 2.6 mg/L to 16.6 mg/L. Bottom DO concentrations averaged 3.7 mg/L and ranged from 0.1 mg/L to 11.0 mg/L. Chlorophyll readings decreased from last week, averaging 36.3 µg/L at the surface and 39.0 µg/L at the bottom. Maximum chlorophyll at the surface reached 121.7 µg/L on the morning of September 1st. 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 4th. Overall, water quality was good at Bullock Reach this week. Salinity averaged 29.5 ppt, 30.8 ppt, and 32.2 ppt at the surface, middle, and bottom sondes, respectively. Surface salinity ranged 26.8– 30.7 ppt, mid salinity ranged 28.4 – 31.8 ppt, and bottom salinity ranged 30.2 – 33.3 ppt. Surface temperature averaged 22.2°C and ranged from 21.0°C to 23.4°C. Mid temperatures averaged 22.1°C and ranged from 21.2°C to 23.1°C. Bottom temperatures averaged 21.6°C and ranged from 20.5°C to 23.0°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 7.3 mg/L and ranged 6.0 – 10.0 mg/L. In the mid waters, DO averaged 6.0 mg/L and ranged 4.0 – 8.7 mg/L. At the bottom, DO averaged 5.0 mg/L and ranged 3.2 – 6.7 mg/L. Chlorophyll readings ranged from low to elevated throughout the week. Readings averaged 9.6 µg/L at the surface, 11.0 µg/L at mid-depth, and 4.8 µg/L at the bottom. The maximum surface chlorophyll was 26.8 µg/L on the morning of September 6th.