Walker Point
Sondes were swapped this week on July 28th. Overall, water quality at Walker Point was poor this week. Weather conditions were rainy this week, with a total of 1.25 inches recorded at T.F. Green, and the majority of rainfall occurring on the 29th. Blackstone River flow reached its peak on July 30th, where the flow greatly exceeded the 20-year daily median flow, and flow remained above the 20-year daily median value for the rest of the week. Salinity at the surface averaged 17.7 ppt and ranged from 7.5 ppt to 27.4 ppt. At the bottom, salinity averaged 26.7 ppt and ranged from 21.6 ppt to 29.4 ppt. Temperatures this week averaged 24.2 °C at the surface and 26.2 °C at the bottom. Surface temperatures ranged from 22.4 °C to 26.2 °C, while bottom temperatures ranged from 22.6 °C to 24.6 °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 a substantial portion of the week. Hypoxic conditions were observed at the bottom for most of July 27th, 28th, August 1st, and August 2nd. Hypoxic conditions occurred intermittently on other days of the week. Surface DO averaged 7.7 mg/L and ranged from 3.5 to 15.1 mg/L. Bottom water DO concentration averaged 2.5 mg/L and ranged from 0.5 mg/L to 6.1 mg/L. Chlorophyll ranged from low to elevated levels throughout the week, averaging 16.2 ug/L at the surface and 5.6 ug/L at the bottom, with evidence of moderate phytoplankton blooms occurring throughout the week. Maximum surface chlorophyll readings reached 66.4 ug/L on the afternoon of August 2nd. 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 August 4th. Overall, water quality ranged from por to good at Bullock Reach this week. Salinity averaged 27.9 ppt, 29.5 ppt, and 31.0 ppt at the surface, middle, and bottom sondes, respectively. Surface salinity ranged from 24.9 to 29.6 ppt, mid salinity ranged from 29.5 to 31.5 ppt, and bottom salinity ranged from 27.3 to 32.5 ppt. Surface temperature averaged 23.9 °C and ranged from 22.8 °C to 25.4 °C. Mid temperatures averaged 23.5 °C and ranged from 21.5 °C to 24.8 °C. Bottom temperatures averaged 22.5 °C and ranged from 20.2 °C to 24.1 °C. DO at Bullock Reach experienced hypoxic conditions (i.e., DO < 2.9 mg/L) towards the beginning of the week in bottom waters, but otherwise did not experience hypoxic conditions. Surface DO averaged 7.2 mg/L and ranged from 5.0 to 11.4 mg/L. In the mid waters, DO averaged 5.9 mg/L and ranged from 3.3 to 9.1 mg/L. At the bottom, DO averaged 4.3 mg/L and ranged 2.2 to 7.6 mg/L. Chlorophyll readings ranged from low to moderate, with evidence of moderate phytoplankton blooms occurring throughout the week. Readings averaged 10.1 µg/L at the surface, 13.0 µg/L at mid-depth, and 4.5 µg/L at the bottom. The maximum surface chlorophyll was 26.8 µg/L on the afternoon of August 2nd.