Historical News
Water Column Clarity
Water clarity was measured at six locations in the Providence River on September 13, 2017. There was no precipitation during the 5 days prior to sampling. Secchi depth ranged from 1.2 meters at both Conimicut Point and Edgewood Yacht Club to 2.0 meters at both Pawtuxet Cove and India Point Park. Overall, Secchi depth averaged 1.6 meters, an increase of 0.3 meters from the previous sampling. Overall, there was no evidence of a north to south gradient in water clarity.
Water Column Clarity
NBC monitoring staff measured water clarity at eight locations in the Providence and Seekonk Rivers on September 7, 2017. A total of 1.61 inches of rain fell during the 5 days prior to sampling, including 0.67 inches on the morning of sampling. Secchi depth ranged from 0.3 meters at Point Street Bridge to 1.9 meters at Bullock Reach and Conimicut Point. Overall, the average Secchi depth decreased by 0.6 meters to 1.3 meters in comparison to the previous survey. The largest decrease (0.8 meters) in water clarity was at the Pawtuxet Cove and India Point Park stations.
Water Column Clarity
Water clarity was measured at eight locations in the Providence and Seekonk Rivers on August 30, 2017. There was 0.26 inches of rainfall recorded on the day of sampling, in the Providence area. Overall, clarity showed an increase compared to the previous survey, with Secchi depth averaging 1.9 meters versus 1.2 m the week before. The maximum water clarity (2.2 m) was observed at India Point; the minimum water clarity (1.4 m) was observed at Pawtuxet Cove. All sites sampled both weeks had an increase in water clarity with the largest increase measured at India Point by 1.3 m compared to the previous survey.
Water Column Clarity
Water clarity was measured at eight locations in the Providence and Seekonk Rivers on August 23, 2017. In the five days before the survey date, there was 0.31 inches of rain recorded in the Providence area. Overall, clarity showed a slight decrease compared to the previous survey, with Secchi depth averaging 1.2 meters versus 1.7 m the week before. The maximum water clarity (1.7 m) was observed at Conimicut Point; the minimum water clarity (0.9 m) was observed at Bullock’s Reach. All sites sampled both weeks decreased in water clarity; the Pomham Rocks site had the largest decrease by 1.3 m compared to the previous survey.
Fixed Site Network
Phillipsdale
At Phillipsdale, sonde data revealed fair water quality conditions over the course of the week. There was 0.27 inches of rainfall during the week recorded in the Providence area. Some stratification as evident at Phillipsdale. Surface salinity was relatively steady throughout the week, minus the daily fluctuations; overall the surface salinity average was 20.8 psu and ranged from 15.4 psu – 24.8 psu. Bottom salinity increased overall throughout the week with daily fluctuations due to tidal influence, and had an average salinity of 26.3 psu and a range of 21.3 psu – 29.6 psu. Surface and bottom temperatures were also decreased from last week by about 1.5 – 2.0oC with surface temperatures averaging 21.7oC and a range of 17.5oC – 23.9oC; bottom temperatures had an average of 22.1oC and ranged between 20.5oC – 23.5oC. Surface chlorophyll was slightly elevated this week with an average of 10.3 ug/L. Dissolved oxygen (DO) for the week was fair at the surface and was lower at the bottom as compared to the previous week. There were some instances of DO below 2.9 mg/L at the surface but no sustained hypoxia; overall DO was fair with an average of 5.4 mg/L and a range of 2.6 mg/L – 10.2 mg/L. Dissolved oxygen in the bottom waters had a weekly average of 2.5 mg/l and ranged from a minimum of 1.0 mg/L to a maximum of 5.3 mg/L. Rolling and daily averages of bottom DO showed consistent hypoxia through the week until the 1st and 2nd when the DO began to increase. Note that tidal fluctuations and Blackstone River flow greatly influence bottom DO, temperature and salinity at this location.
Bullocks Reach
Water quality at Bullocks Reach was good this week. There was a generally uniform water column from surface to bottom with little to no stratification evident. Temperatures at all three depths decreased over the course of the week by about 2oC. Surface water temperature averaged 21.5oC, mid water temperatures had an average of 21.4oC and bottom temperatures averaged 20.7oC. Surface, mid, and bottom salinities all had a slight increase over the course of the week and averaged 28.2 psu, 29.0 psu, and 30.3 psu, respectively. Dissolved oxygen (DO) at all three depths was higher than the previous week and no evidence of hypoxia at any depth. Surface DO had a minimum of 3.1 mg/L, and an average of 4.8 mg/L for the week. At the mid depth DO data showed good conditions with an average of 5.4mg/L and a minimum of 3.3 mg/L. The average weekly bottom DO was 4.2 mg/L with a minimum of 3.1 mg/L. Surface chlorophyll continued to be relatively low with a slight increase from last week with a weekly average of 7.7 ug/L; there was a strong diurnal pattern observed at the surface. Mid chlorophyll was also slightly higher than the previous week with a weekly average of 6.9 ug/L.
