Walker Point
Sondes were swapped this week on September 9th. Overall, water quality at Walker Point was poor to good this week. Weather conditions were extremely rainy this week, with a total of 4.20 inches recorded at T.F. Green, and the majority of rainfall occurring on the 13th. Blackstone River flow was substantially lower than the 20-year daily median flow until September 13th, where flows increased to above the 20-year daily median. Salinity at Walker Point surface averaged 24.7 ppt and ranged from 16.5 ppt to 28.9 ppt. At the bottom, salinity averaged 28.0 ppt and ranged from 14.9 ppt to 30.2 ppt. Temperatures this week averaged 22.6 °C at the surface and 22.7 °C at the bottom. Surface temperatures ranged from 20.8 °C to 24.2°C, while bottom temperatures ranged from 21.7 °C to 23.9 °C.
Dissolved oxygen (DO) at Walker Point remained above the hypoxia threshold at the surface for almost the entire week, but below the hypoxia threshold at the bottom for a portion of the time at the beginning of the week. Hypoxic conditions were observed at the surface only briefly on the morning of September 9th. Hypoxic conditions were observed at the bottom for most of the morning and early of afternoon of September 7th, as well for briefer, more intermittent periods on September 8th and 9th. Surface DO averaged 6.3 mg/L and ranged from 2.5 to 12.1 mg/L. Bottom water DO concentration averaged 4.5 mg/L and ranged from 1.5 mg/L to 9.1 mg/L. Chlorophyll ranged from low to elevated levels throughout the week, averaging 14.6 ug/L at the surface and 17.9 ug/L at the bottom, with evidence of substantial phytoplankton blooms occurring throughout the week. Maximum surface chlorophyll readings reached 41.4 ug/L on the afternoon of September 12th. 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 29.2 ppt, 30.7 ppt, and 31.8 ppt at the surface, middle, and bottom sondes, respectively. Surface salinity ranged from 26.3 to 30.2 ppt, mid salinity ranged from 29.1 to 31.9 ppt, and bottom salinity ranged from 30.7 to 32.7 ppt. Surface temperature averaged 22.3 °C and ranged from 21.1 °C to 23.8 °C. Mid temperatures averaged 22.1 °C and ranged from 21.2 °C to 22.8 °C. Bottom temperatures averaged 21.8 °C and ranged from 21.0 °C to 22.7 °C.
DO at Bullock Reach did not experience hypoxic conditions (i.e., DO < 2.9 mg/L) during the week. Surface DO averaged 7.2 mg/L and ranged from 5.5 to 9.7 mg/L. In the mid waters, DO averaged 6.2 mg/L and ranged from 3.4 to 9.3 mg/L. At the bottom, DO averaged 5.2 mg/L and ranged from 3.3 to 6.9 mg/L. Chlorophyll readings ranged from low to elevated, with evidence of moderate phytoplankton blooms occurring throughout the week. Readings averaged 12.1 µg/L at the surface, 13.9 µg/L at mid-depth, and 8.5 µg/L at the bottom. The maximum surface chlorophyll was 35.8 µg/L on the afternoon of September 12th.