Phillipsdale Landing
Sondes were swapped this week on the morning of September 17th. Overall, water quality at Phillipsdale Landing was good to fair this week. Weather conditions included sporadic rain events, with 0.78 inches of precipitation recorded at T.F. Green. The Blackstone River flow remained below the 20-year daily median. Surface salinity averaged 24.3 ppt and ranged from 20.4 ppt to 28.3 ppt. At the bottom, salinity averaged 26.3 ppt and ranged from 22.9 ppt to 29.6 ppt. Temperatures continued to decline this week, averaging 21.3°C at the surface and ranging 18.5°C – 24.0°C. At the bottom, temperatures averaged 21.4°C and ranged 19.2°C – 23.5°C.
Dissolved oxygen (DO) at Phillipsdale Landing remained above the hypoxia threshold (i.e., DO >2.9 mg/L) throughout the week. Surface DO average 5.97 mg/L and ranged from 3.93 mg/L to 10.82 mg/L. Bottom DO concentrations averaged 5.0 mg/L and ranged from 3.3 mg/L to 8.5 mg/L. Chlorophyll readings decreased from last week, averaging 16.01 µg/L at the surface and 12.8 µg/L at the bottom. Maximum chlorophyll at the surface reached 57.03 µg/L on the evening of September 17th. 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 28.7 ppt, 29.2 ppt, and 30.5 ppt at the surface, middle, and bottom sondes, respectively. Surface salinity ranged 27.5 – 29.7 ppt, mid salinity ranged 27.9 – 30.1 ppt, and bottom salinity ranged 29.0 – 31.4 ppt. Surface temperature averaged 21.0°C and ranged from 19.2°C to 23.1°C. Mid temperatures averaged 20.8°C and ranged from 19.1°C to 22.1°C. Bottom temperatures averaged 20.4°C and ranged from 19.1°C to 21.6°C.
DO at Bullock Reach remained above the hypoxia threshold (i.e., DO >2.9 mg/L) throughout the week Surface DO averaged 6.7 mg/L and ranged 5.5 – 10.2 mg/L. In the mid waters, DO averaged 6.1 mg/L and ranged 4.6 – 8.7 mg/L. At the bottom, DO averaged 5.6 mg/L and ranged 3.8 – 6.7 mg/L. Chlorophyll readings ranged from low to elevated, with evidence of moderate phytoplankton blooms occurring throughout the week. Readings averaged 5.5 µg/L at the surface, 6.2 µg/L at mid-depth, and 6.7 µg/L at the bottom. The maximum surface chlorophyll was 17.5 µg/L on the afternoon of September 16th.