Walker Point
Sondes were swapped this week on August 12th. Overall, water quality at Walker Point was poor to good this week. Weather conditions were mildly rainy this week, with a total of 0.26 inches recorded at T.F. Green, and the majority of rainfall occurring on the 13rd. Blackstone River flow was highest on August 10th, where the flow slightly exceeded the 20-year daily median flow, and flow declined over the rest of the week, falling below the 20-year daily median value. Salinity at the surface averaged 21.8 ppt and ranged from 11.0 ppt to 27.9 ppt. At the bottom, salinity averaged 26.5 ppt and ranged from 23.4 ppt to 28.5 ppt. Temperatures this week averaged 25.3 °C at the surface and 24.7 °C at the bottom. Surface temperatures ranged from 23.2 °C to 27.7 °C, while bottom temperatures ranged from 23.8 °C to 25.8 °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 much of the time, especially towards the beginning of the week. Hypoxic conditions were observed at the surface briefly during the mornings of August 10th, August 12th, August 14th, August 15th, and August 16th. Hypoxic conditions were observed at the bottom for almost the entirety of August 10th and 11th, and in intermittent periods for the rest of the week. Surface DO averaged 7.3 mg/L and ranged from 2.5 to 15.6 mg/L. Bottom water DO concentration averaged 2.7 mg/L and ranged from 0.1 mg/L to 8.4 mg/L. Chlorophyll ranged from low to elevated levels throughout the week, averaging 12.2 ug/L at the surface and 16.4 ug/L at the bottom, with evidence of substantial phytoplankton blooms occurring throughout the week. Maximum surface chlorophyll readings reached 113.0 ug/L on the afternoon of August 13th. 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 poor to good at Bullock Reach this week. Salinity averaged 27.2 ppt, 29.5 ppt, and 31.5 ppt at the surface, middle, and bottom sondes, respectively. Surface salinity ranged from 22.1 to 29.1 ppt, mid salinity ranged from 26.7 to 31.1 ppt, and bottom salinity ranged from 28.2 to 32.4 ppt. Surface temperature averaged 25.3 °C and ranged from 24.0 °C to 27.2 °C. Mid temperatures averaged 24.4 °C and ranged from 23.1 °C to 26.0 °C. Bottom temperatures averaged 23.3 °C and ranged from 22.3 °C to 24.8 °C.
DO at Bullock Reach experienced hypoxic conditions (i.e., DO < 2.9 mg/L) towards the beginning of the week in both middle and bottom waters. Surface DO averaged 7.2 mg/L and ranged from 3.8 to 11.3 mg/L. In the mid waters, DO averaged 4.4 mg/L and ranged from 1.6 to 8.2 mg/L. At the bottom, DO averaged 3.2 mg/L and ranged 2.0 to 5.7 mg/L. Chlorophyll readings ranged from low to moderate, with evidence of moderate phytoplankton blooms occurring throughout the week. Readings averaged 12.3 µg/L at the surface, 11.6 µg/L at mid-depth, and 6.7 µg/L at the bottom. The maximum surface chlorophyll was 44.7 µg/L on the afternoon of August 12th.