Walker Point
Overall, water quality at Walker Point was poor to good this week. Weather conditions were moderately rainy this week, with a total of 0.98 inches recorded at T.F. Green, and the majority of rainfall occurring on 1st. Blackstone River flow was highest on September 3rd, where the flow was somewhat higher than the 20-year daily median flow. Flow decreased after the 3rd. Salinity at Walker Point surface averaged 21.3 ppt and ranged from 15.0 ppt to 27.5 ppt. At the bottom, salinity averaged 27.0 ppt and ranged from 21.9 ppt to 29.8 ppt. Temperatures this week averaged 23.4 °C at the surface and 23.2 °C at the bottom. Surface temperatures ranged from 21.8 °C to 25.6°C, while bottom temperatures ranged from 22.1 °C to 24.1 °C.
Dissolved oxygen (DO) at Walker Point remained above the hypoxia threshold at the surface for most of the week, but below the hypoxia threshold at the bottom for much of the time, especially towards the end of the week. Hypoxic conditions were observed at the surface on the mornings of September 2nd and September 4th. Hypoxic conditions were observed at the bottom intermittently on August 31st, and for extended periods from September 1st – 6th, including one period lasting from 12:45 AM on September 4th to 3:15 PM on September 6th (a duration of 62 hours). Surface DO averaged 5.9 mg/L and ranged from 1.3 to 15.3 mg/L. Bottom water DO concentration averaged 2.5 mg/L and ranged from 0.8 mg/L to 5.2 mg/L. Chlorophyll ranged from low to elevated levels throughout the week, averaging 13.8 ug/L at the surface and 3.1 ug/L at the bottom, with evidence of substantial phytoplankton blooms occurring throughout the week. Maximum surface chlorophyll readings reached 53.1 ug/L on the afternoon of September 5th. 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 1st. Overall, water quality ranged from fair to good at Bullock Reach this week. Salinity averaged 27.9 ppt, 29.8 ppt, and 31.5 ppt at the surface, middle, and bottom sondes, respectively. Surface salinity ranged from 26.0 to 29.4 ppt, mid salinity ranged from 27.8 to 31.7 ppt, and bottom salinity ranged from 29.9 to 32.6 ppt. Surface temperature averaged 23.0 °C and ranged from 21.9 °C to 24.5 °C. Mid temperatures averaged 22.6 °C and ranged from 21.5 °C to 23.6 °C. Bottom temperatures averaged 22.0 °C and ranged from 21.0 °C to 23.1 °C.
DO at Bullock Reach did not experience hypoxic conditions (i.e., DO < 2.9 mg/L) during the week. Surface DO averaged 7.1 mg/L and ranged from 4.8 to 11.3 mg/L. In the mid waters, DO averaged 5.4 mg/L and ranged from 3.6 to 8.1 mg/L. At the bottom, DO averaged 4.2 mg/L and ranged from 3.3 to 6.0 mg/L. Chlorophyll readings ranged from low to moderate, with evidence of moderate phytoplankton blooms occurring throughout the week. Readings averaged 14.4 µg/L at the surface, 11.9 µg/L at mid-depth, and 5.0 µg/L at the bottom. The maximum surface chlorophyll was 55.6 µg/L on the morning of September 5th.