Walker Point
Overall, water quality at Walker Point was poor to good this week. Weather conditions were mildly rainy this week, with a total of 0.24 inches recorded at T.F. Green, and the majority of rainfall occurring on the 20th. Blackstone River flow was highest on the 14th, around the 20-year daily median flow, and then decreased throughout the rest of the week. Salinity at Walker Point surface averaged 20.8 ppt and ranged from 12.8 ppt to 27.2 ppt. At the bottom, salinity averaged 27.3 ppt and ranged from 21.1 ppt to 30.0 ppt. Temperatures this week averaged 21.9 °C at the surface and 22.5 °C at the bottom. Surface temperatures ranged from 19.8 °C to 24.6°C, while bottom temperatures ranged from 21.8 °C to 23.4 °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 briefly on the 15th, 16th, and 18th, as well for a more extended period on September 19th and 20th. Surface DO averaged 8.7 mg/L and ranged from 4.1 to 18.3 mg/L. Bottom water DO concentration averaged 3.9 mg/L and ranged from 1.4 mg/L to 8.3 mg/L. Chlorophyll ranged from low to elevated levels throughout the week, averaging 25.1 ug/L at the surface and 13.4 ug/L at the bottom, with evidence of moderate phytoplankton blooms occurring throughout the week. Maximum surface chlorophyll readings reached 74.0 ug/L on the evening of September 17th. 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 September 16th. Overall, water quality ranged from fair to good at Bullock Reach this week. Salinity averaged 26.9 ppt, 29.3 ppt, and 31.7 ppt at the surface, middle, and bottom sondes, respectively. Surface salinity ranged from 22.5 to 28.4 ppt, mid salinity ranged from 26.8 to 31.2 ppt, and bottom salinity ranged from 30.1 to 32.5 ppt. Surface temperature averaged 21.9 °C and ranged from 20.6 °C to 23.8 °C. Mid temperatures averaged 21.9 °C and ranged from 20.7 °C to 23.2 °C. Bottom temperatures averaged 21.4 °C and ranged from 20.9 °C to 22.2 °C.
DO at Bullock Reach did not experience hypoxic conditions (i.e., DO < 2.9 mg/L) during the week. Surface DO averaged 7.6 mg/L and ranged from 5.6 to 9.8 mg/L. In the mid waters, DO averaged 6.3 mg/L and ranged from 4.1 to 8.6 mg/L. At the bottom, DO averaged 4.6 mg/L and ranged from 3.2 to 6.6 mg/L. Chlorophyll readings ranged from low to moderate, with evidence of moderate phytoplankton blooms occurring throughout the week. Readings averaged 7.8 µg/L at the surface, 7.9 µg/L at mid-depth, and 3.8 µg/L at the bottom. The maximum surface chlorophyll was 20.0 µg/L on the afternoon of September 16th.