Phillipsdale Landing
Overall, water quality at Phillipsdale Landing was good to fair this week. Weather was dry, with no precipitation recorded at T.F. Green. The Blackstone River flow remained below the 20-year daily daily median. Surface salinity averaged 21.6 ppt and ranged from 16.5 ppt to 26.4 ppt. At the bottom, salinity averaged 26.7 ppt and ranged from 21.4 ppt to 29.4 ppt. Temperatures continued to decrease this week, averaging 22.2°C at the surface and ranging 19.1°C – 24.9°C. At the bottom, temperatures averaged 21.5°C and ranged 20.7°C – 23.4°C.
Dissolved oxygen (DO) at Phillipsdale Landing dropped below the hypoxia threshold (i.e., DO >2.9 mg/L) during the week. Surface DO average 10.43 mg/L and ranged from 4.13 mg/L to 18.24 mg/L. Bottom DO concentrations averaged 4.5 mg/L and ranged from 2.5 mg/L to 10.8 mg/L. The longest periods of hypoxic conditions spanned an hour and a half, occurring at the bottom depth on the morning and then again in the afternoon of September 11th. During these periods, bottom DO averaged around 2.62 mg/L and 2.79 mg/L, respectively. Chlorophyll readings increased from last week, averaging 51.20 µg/L at the surface and 32.3 µg/L at the bottom. Maximum chlorophyll at the surface reached 95.4 µg/L on the evening of September 13th. 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 10th. Overall, water quality was good at Bullock Reach this week. Salinity averaged 28.4 ppt, 29.2 ppt, and 30.8 ppt at the surface, middle, and bottom sondes, respectively. Surface salinity ranged 27.0 – 29.1 ppt, mid salinity ranged 27.7 – 30.4 ppt, and bottom salinity ranged 30.0 – 31.5 ppt. Surface temperature averaged 21.3°C and ranged from 20.2°C to 23.4°C. Mid temperatures averaged 20.9°C and ranged from 20.1°C to 22.6°C. Bottom temperatures averaged 20.2°C and ranged from 19.3°C to 21.1°C. DO at Bullock Reach remained above the hypoxia threshold (i.e., DO >2.9 mg/L) throughout the week. Surface DO averaged 8.3 mg/L and ranged 6.1 – 11.3 mg/L. In the mid waters, DO averaged 6.6 mg/L and ranged 4.7 – 9.7 mg/L. At the bottom, DO averaged 4.5 mg/L and ranged 3.4 – 6.6 mg/L. Chlorophyll readings ranged from low to elevated, with evidence of moderate phytoplankton blooms occurring throughout the week. Readings averaged 12.0 µg/L at the surface, 12.7 µg/L at mid-depth, and 6.9 µg/L at the bottom. The maximum surface chlorophyll was 30.7 µg/L on the afternoon of September 9th.