Walker Point
Sondes were swapped this week on September 22nd. Overall, water quality at Walker Point was poor to good this week. Weather conditions were rainy this week, with a total of 3.77 inches recorded at T.F. Green, and the majority of rainfall occurring on the 26th and 27th. Blackstone River flow remained relatively steady until the 26th, under the 20-year daily median flow, before increasing substantially on the 26th and 27th. Salinity at Walker Point surface averaged 23.6 ppt and ranged from 15.8 ppt to 30.5 ppt. At the bottom, salinity averaged 29.2 ppt and ranged from 22.0 ppt to 31.3 ppt. Temperatures this week averaged 18.7 °C at the surface and 19.9 °C at the bottom. Surface temperatures ranged from 16.6 °C to 20.8°C, while bottom temperatures ranged from 17.2 °C to 21.9 °C.
Dissolved oxygen (DO) at Walker Point remained above the hypoxia threshold at the surface, but below the hypoxia threshold at the bottom for portions of the week. Hypoxic conditions were observed at the bottom for extended periods on September 21st – 23rd. Surface DO averaged 6.4 mg/L and ranged from 4.3 to 9.1 mg/L. Bottom water DO concentration averaged 3.9 mg/L and ranged from 1.4 mg/L to 6.7 mg/L. Chlorophyll ranged from low to mildly elevated levels throughout the week, averaging 5.8 ug/L at the surface and 1.7 ug/L at the bottom, with evidence of small phytoplankton blooms occurring throughout the week. Maximum surface chlorophyll readings reached 18.4 ug/L on the early morning of September 21st. 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. Bottom data is not available much of the week (starting on September 22nd), as multiple sensors stopped recording reliable data. Salinity averaged 28.8 ppt, 29.9 ppt, and 31.5 ppt at the surface, middle, and bottom sondes, respectively. Surface salinity ranged from 24.6 to 30.5 ppt, mid salinity ranged from 27.6 to 31.4 ppt, and bottom salinity ranged from 29.2 to 33.3 ppt. Surface temperature averaged 19.0 °C and ranged from 17.2 °C to 21.1 °C. Mid temperatures averaged 19.1 °C and ranged from 17.4 °C to 20.9 °C. Bottom temperatures averaged 20.5 °C and ranged from 19.9 °C to 21.2 °C.
DO at Bullock Reach did not experience hypoxic conditions (i.e., DO < 2.9 mg/L) during the week. Surface DO averaged 7.0 mg/L and ranged from 5.9 to 8.2 mg/L. In the mid waters, DO averaged 7.0 mg/L and ranged from 5.6 to 7.7 mg/L. At the bottom, DO averaged 4.5 mg/L and ranged from 3.3 to 6.3 mg/L. Chlorophyll readings ranged from low to moderate, with evidence of mild phytoplankton blooms occurring throughout the week. Readings averaged 4.9 µg/L at the surface, 7.0 µg/L at mid-depth, and 4.2 µg/L at the bottom. The maximum surface chlorophyll was 9.9 µg/L on the evening of September 24th.