Phillipsdale Landing
Sondes were swapped this week on the morning of August 14th. Overall, the water quality at Phillipsdale Landing was good to fair this week. Weather conditions included sporadic rain events, with 0.37 inches of precipitation recorded at T.F. Green. The Blackstone River flow fluctuated throughout the week. Surface salinity averaged 20.7 ppt and ranged from 12.2 ppt to 25.0 ppt. At the bottom, salinity averaged 24.8 ppt and ranged from 19.1 ppt to 29.3 ppt. Temperatures averaged 25.6°C at the surface and 25.2°C at the bottom. Surface temperatures ranged from 22.0°C to 27.9°C, while bottom temperatures ranged from 24.1°C to 26.8°C.
Dissolved oxygen (DO) at Phillipsdale Landing remained the hypoxia threshold (i.e., DO >2.9 mg/L) at the surface, while DO at the bottom waters dropped below the hypoxic threshold throughout the week. The longest period of hypoxic conditions spanned 6 hours, occurring during the day of August 16th. During this period, the bottom DO averaged around 2.32 mg/L. Surface DO averaged 6.9 mg/L and ranged from 3.2 mg/L to 13.3 mg/L. Bottom DO concentrations averaged 4.2 mg/L and ranged from 1.4 mg/L to 12.4 mg/L. Chlorophyll readings decreased from last week, averaging 26.7 µg/L at the surface and 27.0 µg/L at the bottom. Maximum chlorophyll at the surface reached 154.4 µg/L on the morning of August 16th. 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 to fair at Bullock Reach this week. Salinity averaged 28.2 ppt, 29.5 ppt, and 30.4 ppt at the surface, middle, and bottom sondes, respectively. Surface salinity ranged 26.0– 29.6 ppt, middle salinity ranged 0.0 – 30.7 ppt, and bottom salinity ranged 29.2 – 31.3 ppt. Surface temperature averaged 25.0°C and ranged from 23.5°C to 26.5°C. Middle temperature averaged 24.3°C and ranged from 22.7°C to 25.8°C. Bottom temperatures averaged 23.2°C and ranged from 21.3°C to 24.9°C.
Dissolved oxygen (DO) at Bullock Reach remained above the hypoxia threshold (i.e., DO >2.9 mg/L) at the surface and middle depths throughout the week. DO at the bottom waters dropped below the hypoxic threshold for half an hour on the morning of August 11th. Surface DO averaged 7.5 mg/L and ranged 5.6 – 10.1 mg/L. At the middle depth, DO averaged 5.9 mg/L and ranged 3.9 – 8.6 mg/L. At the bottom, DO averaged 4.4 mg/L and ranged 2.4 – 6.4 mg/L. Chlorophyll readings ranged from low to elevated throughout the week. Readings averaged 16.3 µg/L at the surface, 10.1 at the middle, and 3.7 µg/L at the bottom. The maximum surface chlorophyll was 34.4 µg/L on the afternoon of August 15th.