Phillipsdale Landing
Sondes were swapped this week on July 1st. Overall, water quality at Phillipsdale Landing was poor to good this week. Weather conditions were moderately rainy this week, with a total of 0.55 inches recorded at T.F. Green, and the majority of rainfall occurring on the 3rd. Blackstone River flow reached its peak on July 3rd, where the flow was similar to the 20-year daily median flow, but was otherwise below the 20-year daily median value for the rest of the week. Salinity at the surface averaged 15.5 ppt and ranged from 6.5 ppt to 23.3 ppt. At the bottom, salinity averaged 23.8 ppt and ranged from 16.1 ppt to 28.5 ppt. Temperatures this week averaged 24.6 °C at the surface and 22.3 °C at the bottom. Surface temperatures ranged from 21.8 °C to 28.5 °C, while bottom temperatures ranged from 20.2 °C to 24.9 °C.
Dissolved oxygen (DO) at Phillipsdale Landing remained above the hypoxia threshold (i.e., DO >2.9 mg/L) at the surface, but below the hypoxia threshold at the bottom for most of the week. Hypoxic conditions were observed at the surface briefly during the morning on July 1st. Hypoxic conditions were observed at the bottom for multiple extended periods from July 2nd to July 6th, including one 21-hour period from the evening of July 2nd to the evening of July 3rd. Surface DO averaged 9.4 mg/L and ranged from 2.8 to 20.8 mg/L. Bottom water DO concentration averaged 2.8 mg/L and ranged from 0.8 mg/L to 8.8 mg/L. Chlorophyll ranged from low to elevated levels throughout the week, averaging 38.6 ug/L at the surface and 34.7 ug/L at the bottom, with evidence of substantial phytoplankton blooms occurring throughout the week. Maximum surface chlorophyll readings reached 113.1 ug/L on the afternoon of July 5th. 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 ranged from fair to good at Bullock Reach this week. Salinity averaged 27.0 ppt, 29.0 ppt, and 30.8 ppt at the surface, middle, and bottom sondes, respectively. Surface salinity ranged from 24.9 to 28.7 ppt, mid salinity ranged from 26.2 to 30.8 ppt, and bottom salinity ranged from 29.3 to 31.9 ppt. Surface temperature averaged 23.4 °C and ranged from 21.4 °C to 25.3 °C. Mid temperatures averaged 22.3 °C and ranged from 20.0 °C to 24.5 °C. Bottom temperatures averaged 20.2 °C and ranged from 19.0 °C to 23.3 °C.
DO at Bullock Reach remained above the hypoxia threshold (i.e., DO >2.9 mg/L) throughout the week. Surface DO averaged 7.4 mg/L and ranged from 5.2 to 10.2 mg/L. In the mid waters, DO averaged 5.9 mg/L and ranged from 3.9 to 8.6 mg/L. At the bottom, DO averaged 4.6 mg/L and ranged 3.0 to 7.1 mg/L. Chlorophyll readings ranged from low to moderate, with evidence of moderate phytoplankton blooms occurring throughout the week. Readings averaged 10.1 µg/L at the surface, 13.1 µg/L at mid-depth, and 9.2 µg/L at the bottom. The maximum surface chlorophyll was 32.8 µg/L on the afternoon of July 4th.