Historical News
Water Column Clarity
Water clarity was measured at seven locations in the Providence and Seekonk Rivers on September 6, 2018. There was no recorded precipitation in the five days prior to sampling, but there was 0.18 inches of rain on the day of sampling. Overall, average water clarity was the same as the previous week, at 1.4 m. Decreases in water clarity were observed at India Point Park and Conimicut Point. Water clarity increased at Pomham Rocks, Edgewood Yacht Club, and Bullock Reach. The largest increase of 0.90 m occurred at Bullock Reach. Secchi depth ranged from 0.80 m at India Point Park to 1.80 m at Bullock Reach. There was evidence of a north to south water clarity gradient.
Nutrients Sampling
Seven bay stations and eight river stations were sampled for nutrients on August 1, 2018. Surface and bottom waters were sampled at all seven bay stations. There was no recorded rainfall in the three days prior to sampling.
Among the river stations sampled, the highest average total nitrogen (TN) and total dissolved nitrogen (TDN) concentrations, 1875 ppb and 1890 ppb, respectively, were observed at the Ten Mile River sampling location at Central Avenue. At the Moshassuck River at Higginson Avenue, TN and TDN concentrations were lowest among all river sites. At this site, both TN and TDN concentrations were approximately 590 ppb. The highest dissolved inorganic nitrogen (DIN) concentration was observed at Ten Mile River at Central Avenue, at 1715 ppb, while the lowest DIN result, 438 ppb, occurred at Woonasquatucket River at Manton Avenue.
Among surface samples from bay sites, the highest TN, TDN, and DIN concentrations were measured at Pawtuxet Cove, with results of 1,000 ppb, 527 ppb, and 305 ppb, respectively. The lowest surface TN concentration (665 ppb) was observed at Conimicut Point, while the lowest surface TDN concentration (177 ppb) was observed at Bullock Reach. Lowest DIN values (<13 ppb) were observed at Conimicut Point and Bullock Reach, where nitrate-nitrite and ammonia were below detection limits. Chlorophyll a averaged 32.8 ug/L throughout the bay, ranging from 3.2 ug/L at Phillipsdale Landing to 92.3 ug/L at India Point Park.
Results from nutrient sampling completed on August 16 and August 29-30 are pending final analysis from the NBC Laboratory. The next anticipated date of sampling is September 12, 2018.
Fixed Site Network
Phillipsdale
This week at Phillipsdale, data revealed fair to poor water quality, with some stratification observed at the beginning of the week, which lessened slightly as the week went on. There was 0.30 inches of rainfall during the week with increasing flow from the Blackstone River due to this rainfall. Surface salinity remained relatively high for this site with an average of 19.5 ppt, with a minimum of 9.1 ppt, and a maximum of 25.4 ppt. Bottom salinity increased slightly and had an average of 24.7 ppt and a range 18.3 ppt – 28.5 ppt. Surface and bottom temperatures were similar and also relatively stable as compared to last week; surface temperature averaged 25.1oC with a range of 22.3oC – 28.2oC; bottom temperatures had a weekly average of 24.8oC and a range of 23.3oC – 26.7oC. Surface chlorophyll was still elevated and decreased throughout the week; the weekly average for surface chlorophyll was 33.9 ug/L, and a daily average peak of about 48 ug/L on the 4th. Dissolved oxygen (DO) for the week was fair at the surface and relatively poor at the bottom. Surface DO had a weekly average was 5.4 mg/L with a minimum of 0.5 mg/L. Dissolved oxygen in the bottom waters was similar to last week, though there were still extended periods of hypoxia almost daily. The weekly average for bottom DO was 3.0 mg/l and a minimum of 1.1 mg/L; the 5th, 7th, and 8th all had a daily average of 2.9 mg/L or below. Note that tidal fluctuations and Blackstone River flow greatly influence bottom DO, temperature and salinity at this location.
Bullock Reach
The Bullock’s Reach sondes data revealed good to fair water quality conditions over the week, with a relatively well mixed water column. Temperatures had an overall increase at all three depths as compared to the prior week averaging 25.0oC at the surface, 24.3oC at the mid, and 22.8oC at the bottom. Salinities were relatively stable during the week, with an average at the surface of 27.2 ppt, a mid-depth average of 28.8 ppt, and a bottom salinity average of 30.4 ppt. Chlorophyll at the surface was still elevated and similar to concentrations seen in the prior week; surface chlorophyll peaked at about 14.5 ug/L on the 8th and averaged 12.0 ug/L for the week; mid chlorophyll averaged 6.2 ug/L, and bottom chlorophyll averaged 4.4 ug/L. Dissolved oxygen (DO) was good at the surface and fair at the mid depth and bottom. Surface DO averaged 6.3 mg/L with a minimum of 4.4 mg/L; mid-depth DO averaged 5.1 mg/L and a minimum of 2.6 mg/L. Bottom DO was still fair though much improved towards the end of the week, with a few instances of hypoxia mostly at the beginning of the week; there were no days with a daily average of less than 2.9 mg/L. The weekly bottom DO average was 3.6 mg/L, with a minimum of 2.5 mg/L.
Fixed Site Network
Phillipsdale
This week at Phillipsdale, data revealed fair to poor water quality, with some stratification observed at the beginning of the week, which lessened slightly as the week went on. There was no rainfall during the week and flow from the Blackstone River decreased through the week.. Both the surface and bottom salinity increased through the week with surface salinity averaging 15.9 ppt, with a minimum of 6.0 ppt, and a maximum of 24.3 ppt. Bottom salinity also increased and had an average of 23.6 ppt and a range 15.0 ppt – 28.9 ppt. Surface and bottom temperatures were similar to each other this week and increased as compared to last week; surface temperature averaged 25.2oC with a range of 22.4oC – 28.8oC; bottom temperatures had a weekly average of 24.4oC and a range of 23.0oC – 26.7oC. Surface chlorophyll was elevated though decreased substantially towards the end of the week; the weekly average for surface chlorophyll was 36.0 ug/L, and a daily average peak of about 54 ug/L on the 30th. Dissolved oxygen (DO) for the week was fair at the surface and relatively poor at the bottom. Surface DO had a weekly average was 6.8 mg/L with a minimum of 1.8 mg/L. Dissolved oxygen in the bottom waters was better than last week, though there were still a few extended periods of hypoxia particularly at the end of the week. The weekly average for bottom DO was 3.2 mg/l and a minimum of 1.3 mg/L; the 31st and 1st were the only days during the week with a daily average of less than 2.9 mg/L. Note that tidal fluctuations and Blackstone River flow greatly influence bottom DO, temperature and salinity at this location.
Bullock Reach
The Bullock’s Reach sondes data revealed fair water quality conditions over the week, with some stratification apparent throughout the week. Temperatures had an overall increase at all three depths as compared to the prior week averaging 25.1oC at the surface, 23.9oC at the mid, and 22.3oC at the bottom. Salinities were relatively stable during the week, with an average at the surface of 26.5 ppt, a mid-depth average of 28.9 ppt, and a bottom salinity average of 30.8 ppt. Chlorophyll at the surface was elevated but decreased from last week; chlorophyll peaked at about 13.5 ug/L on the 28th ; surface chlorophyll averaged 11.4 ug/L for the week, mid chlorophyll averaged 5.7 ug/L, and bottom chlorophyll averaged 4.1 ug/L. Dissolved oxygen (DO) was good at the surface and fair at the mid depth and bottom. Surface DO averaged 7.2 mg/L with a minimum of 4.9 mg/L; mid-depth DO averaged 5.0 mg/L and a minimum of 3.2 mg/L. Bottom DO was still fair and similar to the previous week, with some instances of hypoxia mostly towards the end of the week, but there were no days with a daily average of less than 2.9 mg/L. The weekly bottom DO average was 3.5mg/L, with a minimum of 2.2 mg/L.
Fixed Site Network
Phillipsdale
This week at Phillipsdale, data revealed fair to poor water quality, with some stratification observed at the beginning of the week, which lessened slightly as the week went on. There was 0.28 inches of rain during the week; flow from the Blackstone River generally decreased through the week, though it was still higher than average. Both the surface and bottom salinity increased slightly; surface salinity had an overall average for the week of 10.4 ppt, with a minimum of 5.4 ppt, and a maximum of 17.2 ppt. Bottom salinity also decreased had an average of 23.2 ppt and a range 10.7 ppt – 28.8 ppt. Surface and bottom temperatures were similar to each other this week and decreased as compared to last week; surface temperature averaged 24.1oC with a range of 20.7oC – 26.1oC; bottom temperatures had a weekly average of 23.9oC and a range of 22.5oC – 25.3oC. Surface chlorophyll steadily increased through the week and was still elevated with a weekly average of 14.8 ug/L, and a daily average peak of about 30 ug/L at the end of the week. Dissolved oxygen (DO) for the week was fair at the surface and relatively poor at the bottom. Surface DO was increased as compared to last week and had a weekly average was 7.0 mg/L with a minimum of 2.7 mg/L. Dissolved oxygen in the bottom waters had extended periods of hypoxia throughout the week with a weekly average of 1.4 mg/l and a minimum of 0.1 mg/L; all days, except for the 25th, had daily averages of 2.0 mg/L or below. Note that tidal fluctuations and Blackstone River flow greatly influence bottom DO, temperature and salinity at this location.
Bullock's Reach
The Bullock’s Reach sondes data revealed fair water quality conditions over the week, with stratification apparent throughout the week. The bottom waters had improving dissolved oxygen over the course of the week, with much less hypoxia evident as compared the the prior week. Temperatures continued to decrease at all three depths as compared to the prior week averaging 24.0oC at the surface, 23.5oC at the mid, and 21.9oC at the bottom. Salinities increased at all three depths over the week, with an average at the surface of 26.3 ppt, a mid-depth average of 29.6 ppt, and a bottom salinity average of 32.1 ppt. Chlorophyll at the surface was elevated throughout the week, peaking at nearly 25.0 ug/L on the 22nd ; surface chlorophyll averaged 15.9 ug/L for the week, mid chlorophyll averaged 10.7 ug/L, and bottom chlorophyll averaged 4.0 ug/L. Dissolved oxygen (DO) was good at the surface and fair at the mid depth and bottom. Surface DO averaged 7.7 mg/L with a minimum of 4.6 mg/L; mid-depth DO averaged 4.6 mg/L and a minimum of 1.7 mg/L. Bottom DO was considerably better than the previous week, with some instances of hypoxia mostly towards the end of the week, but there were no days with an daily average of less than 2.9 mg/L. The weekly bottom DO average was 3.9 mg/L, with a minimum of 2.4 mg/L.
