Walker Point
Overall, water quality at Walker Point was poor this week. Weather conditions were rainy this week, with a total of 2.52 inches recorded at T.F. Green, and the majority of rainfall occurring on the 3rd. Blackstone River flow reached its peak on August 4th, where the flow greatly exceeded the 20-year daily median flow, and flow remained above the 20-year daily median value for the rest of the week. Salinity at the surface averaged 11.3 ppt and ranged from 3.6 ppt to 22.5 ppt. At the bottom, salinity averaged 24.3 ppt and ranged from 18.4 ppt to 28.5 ppt. Temperatures this week averaged 26.0 °C at the surface and 24.4 °C at the bottom. Surface temperatures ranged from 23.7 °C to 29.8 °C, while bottom temperatures ranged from 23.7 °C to 25.4 °C.
Dissolved oxygen (DO) at Walker Point 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 August 3rd. Hypoxic conditions were observed at the bottom for almost the entire week. Surface DO averaged 9.5 mg/L and ranged from 2.8 to 19.3 mg/L. Bottom water DO concentration averaged 1.6 mg/L and ranged from 0.1 mg/L to 3.9 mg/L. Chlorophyll ranged from low to elevated levels throughout the week, averaging 18.0 ug/L at the surface and 3.5 ug/L at the bottom, with evidence of substantial phytoplankton blooms occurring throughout the week. Maximum surface chlorophyll readings reached 157.4 ug/L on the morning of August 9th. 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 August 4th. Overall, water quality ranged from fair to good at Bullock Reach this week. Salinity averaged 23.8 ppt, 28.0 ppt, and 31.1 ppt at the surface, middle, and bottom sondes, respectively. Surface salinity ranged from 19.9 to 28.7 ppt, mid salinity ranged from 24.1 to 31.0 ppt, and bottom salinity ranged from 28.7 to 32.3 ppt. Surface temperature averaged 26.1 °C and ranged from 24.1 °C to 28.5 °C. Mid temperatures averaged 24.7 °C and ranged from 23.1 °C to 27.0 °C. Bottom temperatures averaged 23.2 °C and ranged from 22.3 °C to 24.7 °C.
DO at Bullock Reach experienced hypoxic conditions (i.e., DO < 2.9 mg/L) towards the end of the week in both middle and bottom waters. Surface DO averaged 8.1 mg/L and ranged from 4.9 to 14.2 mg/L. In the mid waters, DO averaged 4.9 mg/L and ranged from 1.1 to 8.4 mg/L. At the bottom, DO averaged 3.6 mg/L and ranged 1.8 to 7.4 mg/L. Chlorophyll readings ranged from low to moderate, with evidence of moderate phytoplankton blooms occurring throughout the week. Readings averaged 15.5 µg/L at the surface, 14.8 µg/L at mid-depth, and 4.9 µg/L at the bottom. The maximum surface chlorophyll was 37.2 µg/L on the afternoon of August 5th.