Phillipsdale Landing
Overall, the water quality at Phillipsdale Landing was fair this week. Weather conditions included frequent rain events this week, with 2.33 inches of precipitation recorded at T.F. Green. The Blackstone River flow fluctuated throughout the week. Surface salinity averaged 11.1 ppt and ranged from 2.9 ppt to 22.5 ppt. At the bottom, salinity averaged 21.3 ppt and ranged from 5.1 ppt to 28.2 ppt. Surface temperature increased this week, averaging 25.0°C at the surface and ranging 22.9°C – 28.8°C. The bottom temperature decreased averaged 21.3°C and ranged 5.1°C – 28.2°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 22.5 hours, occurring at the bottom depth from the afternoon of July 9th until July 10th. During this period, the bottom DO averaged around 1.69 mg/L. Surface DO averaged 7.1 mg/L and ranged from 2.1 mg/L to 13.2 mg/L. Bottom DO concentrations averaged 2.9 mg/L and ranged from 0.4 mg/L to 8.1 mg/L. Chlorophyll readings decreased from last week, averaging 24.8 µg/L at the surface and 24.0 µg/L at the bottom. Maximum chlorophyll at the surface reached 97.0 µg/L on the morning of July 8th. 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 July 9th. Overall, water quality was good at Bullock Reach this week. Salinity averaged 25.8 ppt, 28.7 ppt, and 30.8 ppt at the surface, middle, and bottom sondes, respectively. Surface salinity ranged 22.3– 28.5 ppt, mid salinity ranged 25.2 – 29.3 ppt, and bottom salinity ranged 29.0 – 31.9 ppt. Surface temperature averaged 24.5°C and ranged from 23.0°C to 26.0°C. Mid temperatures averaged 24.3°C and ranged from 23.3°C to 25.3°C. Bottom temperatures averaged 20.7°C and ranged from 18.4°C to 23.6°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 3.8 – 11.6 mg/L. In the mid waters, DO averaged 6.6 mg/L and ranged 4.7 – 7.8 mg/L. At the bottom, DO averaged 3.8 mg/L and ranged 2.9 – 6.2 mg/L. Chlorophyll readings ranged from low to elevated throughout the week. Readings averaged 14.2 µg/L at the surface, 13.5 µg/L at mid-depth, and 4.8 µg/L at the bottom. The maximum surface chlorophyll was 58.9 µg/L on the afternoon of July 13th.