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 1.33 inches recorded at T.F. Green, and the majority of rainfall occurring on the 21st. Blackstone River flow was highest on August August 23rd, where the flow slightly exceeded the 20-year daily median flow. Flow previous in the week was below the 20-year daily median value. Salinity at the surface averaged 20.6 ppt and ranged from 13.8 ppt to 27.4 ppt. At the bottom, salinity averaged 27.8 ppt and ranged from 24.1 ppt to 30.4 ppt. Temperatures this week averaged 23.9 °C at the surface and 24.0 °C at the bottom. Surface temperatures ranged from 21.7 °C to 26.3°C, while bottom temperatures ranged from 22.2 °C to 25.1 °C.
Dissolved oxygen (DO) at Walker Point remained above the hypoxia threshold (i.e., DO >2.9 mg/L) at the surface for most of the week, but below the hypoxia threshold at the bottom for much of the time, especially towards the beginning of the week. Hypoxic conditions were observed at the surface briefly during the mornings of August 19th, August 22nd, and August 23rd, August 15th, and August 16th, with a more extended hypoxic period was observed on the morning of August 18th, lasting approximately 2.5 hours. Hypoxic conditions were observed at the bottom for almost the entirety of August 18th – 24th, and in intermittent periods on August 17th. Surface DO averaged 7.3 mg/L and ranged from 1.2 to 20.4 mg/L. Bottom water DO concentration averaged 1.0 mg/L and ranged from 0 mg/L to 4.2 mg/L. Chlorophyll ranged from low to very elevated levels throughout the week, averaging 26.7 ug/L at the surface and 22.4 ug/L at the bottom, with evidence of substantial phytoplankton blooms occurring throughout the week. Maximum surface chlorophyll readings reached 467.0 ug/L on the afternoon of August 23rd. 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 18th. Overall, water quality ranged from poor to good at Bullock Reach this week. Salinity averaged 27.6 ppt, 29.3 ppt, and 31.2 ppt at the surface, middle, and bottom sondes, respectively. Surface salinity ranged from 25.8 to 29.4 ppt, mid salinity ranged from 27.6 to 31.1 ppt, and bottom salinity ranged from 26.5 to 32.4 ppt. Surface temperature averaged 24.0 °C and ranged from 22.0 °C to 25.9 °C. Mid temperatures averaged 23.6 °C and ranged from 22.0 °C to 25.2 °C. Bottom temperatures averaged 22.5 °C and ranged from 20.5 °C to 24.1 °C.
DO at Bullock Reach experienced hypoxic conditions (i.e., DO < 2.9 mg/L) intermittently in both middle and bottom waters. Surface DO averaged 6.2 mg/L and ranged from 3.1 to 10.8 mg/L. In the mid waters, DO averaged 4.9 mg/L and ranged from 2.6 to 7.7 mg/L. At the bottom, DO averaged 3.7 mg/L and ranged 2.3 to 5.5 mg/L. Chlorophyll readings ranged from low to moderate, with evidence of moderate phytoplankton blooms occurring throughout the week. Readings averaged 9.2 µg/L at the surface, 10.9 µg/L at mid-depth, and 3.5 µg/L at the bottom. The maximum surface chlorophyll was 31.7 µg/L on the afternoon of August 17th.