2014 Dissolved Oxygen Assessment CHRP Meeting December 17, 2014 Heather Stoffel.

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2014 Dissolved Oxygen Assessment CHRP Meeting December 17, 2014 Heather Stoffel

Transcript of 2014 Dissolved Oxygen Assessment CHRP Meeting December 17, 2014 Heather Stoffel.

Page 1: 2014 Dissolved Oxygen Assessment CHRP Meeting December 17, 2014 Heather Stoffel.

2014 Dissolved Oxygen Assessment

CHRP MeetingDecember 17, 2014

Heather Stoffel

Page 2: 2014 Dissolved Oxygen Assessment CHRP Meeting December 17, 2014 Heather Stoffel.

5/215/2

65/3

16/5

6/106/1

56/2

06/2

56/3

07/5

7/107/1

57/2

07/2

57/3

08/4 8/9

8/148/1

98/2

48/2

99/3 9/8

9/139/1

89/2

39/2

80.0

1.0

2.0

3.0

4.0

5.0

6.0

7.0

8.0

9.0

BR CP NP MV QP

Dis

solv

ed O

xyge

n (m

g/L)

Daily Bottom Oxygen Levels for Upper Bay and West Passage

Page 3: 2014 Dissolved Oxygen Assessment CHRP Meeting December 17, 2014 Heather Stoffel.

This is the over all range of exceedences for each station for all years of data in a down bay gradient. The ranges considers inter-annual variability due to weather. An exceedence is greater than 1 day. The Seekonk (PD) to Mt View (MV) and Poppasquash Pt (PP) are consistently in exceedence every year. That is why this area is listed as impaired for dissolved oxygen. Areas of concern are areas like Quonset Pt (QP). The Seekonk, Providence River, and Greenwich Bay have the worst exceedence with average exceedences of a month or more a year.

Page 4: 2014 Dissolved Oxygen Assessment CHRP Meeting December 17, 2014 Heather Stoffel.

Seasonal Cumulative River Flow from the Blackstone River and Seasonal Mean Surface Temperature from North Prudence Station

2001 2002 2003 2004 2005 2006 2007 2008 2009 2010 2011 2012 2013 20140

20,000

40,000

60,000

80,000

100,000

120,000

18

19

20

21

22

23

24

Sept Aug July June Temperature (C, NP-S)

Flo

w

(cu

.ft.

/se

c) T

em

pe

ratu

re ( C

)

Page 5: 2014 Dissolved Oxygen Assessment CHRP Meeting December 17, 2014 Heather Stoffel.

mph

°

Seasonal wind directions tend to be from the SSW.

Dry seasons (7.83 mph) tend to have slightly higher average wind speed compared to wet seasons (7.35 mph).

2012 had lowest wind speed for dry season (7.02 mpH)

2009 had SSE wind direction

Dry Years

Wet Years

(2002, 2005, 2007, 2010, 2014)

(2001, 2003, 2004, 2006, 2008, 2009, 2011, 2013)

Page 6: 2014 Dissolved Oxygen Assessment CHRP Meeting December 17, 2014 Heather Stoffel.

PD BR CP NP GB SR MV QP PP MH0

10

20

30

40

50

60

70

Exceedences During Dry Years

200220052007201020122014

RID

OCS

Day

s

Page 7: 2014 Dissolved Oxygen Assessment CHRP Meeting December 17, 2014 Heather Stoffel.

PD BR CP NP GB SR MV QP GD PP MH TW0

20

40

60

80

100

120

Exceedences During Wet Years

20012003200420062008200920112013RI

DO

CS D

ays

Page 8: 2014 Dissolved Oxygen Assessment CHRP Meeting December 17, 2014 Heather Stoffel.

Dissolved Oxygen Exceedences Over Time

North Prudence is showing a downward trend towards compliance. An exceedence is 1 day. The Providence River is in exceedence consistently over all years.

(Grouped data in 5 year intervals with the exceptions of 2011-2014 * indicates not complete dataset.)

PD (2004-2005)*

BR (2001-2005)

CP (2003, 2005)*

NP (2001-2005)

PD (2006-2010)

BR (2006-2010)

CP (2006-2010)

NP (2006-2010)

PD (2011-2013)*

BR (2011-2014)

CP (2011-2014)

NP (2011-2014)

0

20

40

60

80

100

120

Dissolved Oxygen Exceedence Ranges for Upper Bay from 2001-2014

5 year intervals for Upper Bay Stations

RI D

OCS

(Day

s)

Page 9: 2014 Dissolved Oxygen Assessment CHRP Meeting December 17, 2014 Heather Stoffel.

0 5 10 15 20 25 30 350

1

2

3

4

5

6

7

BR CP NP GB SR MV QP PP MH

Surface Chlorophyll (ug/L)

Bo

tto

m D

iss

olv

ed

Ox

yg

en

(m

g/L

)Comparison of Seasonal Average Surface Chlorophyll Levels to

Bottom Dissolved Oxygen in Upper Narragansett Bay

R²= -0.597p< 0.00005

Page 10: 2014 Dissolved Oxygen Assessment CHRP Meeting December 17, 2014 Heather Stoffel.

Chlorophyll as an Indicator

• Many New England and Mid-Atlantic estuaries use 20 ug/L as a threshold during the growing season (i.e., EPA-National Coastal Condition Reports (NCCR) threshold)

• The figure showing the relationship between low bottom oxygen and surface chlorophyll also shows that on average seasonally Bullock Reach and Greenwich Bay are consistently over the 20 ug/L threshold (which under the EPA-NCCR definition would be “poor” water quality for chlorophyll)

• Many of Upper Narragansett Bay stations have events with peaks above the 20 ug/L threshold

Page 11: 2014 Dissolved Oxygen Assessment CHRP Meeting December 17, 2014 Heather Stoffel.

From the Seekonk River to North Prudence on average is considered eutrophic based on EPA definitions. Mt View and Quonset have episodic events at eutrophic levels. (Data (2001-2012) June 1-Sept 30)

PD BR CP NP MV QP GD0

20406080

100120140160180200220240 Summer Chlorophyll Ranges in Narragansett

Bay

Stations - North to South

Chlo

roph

yll R

ange

(ug/

L)

Page 12: 2014 Dissolved Oxygen Assessment CHRP Meeting December 17, 2014 Heather Stoffel.

Comparison of Chlorophyll Seasonal Ranges for Upper Bay and West Passage Stations

BR (01-05) BR (06-10) BR (11-14) NP (01-05)* NP (06-10)* NP (11-14) MV (04-05)*

MV (06-10) MV (11-14)0

102030405060708090

100110120130140150

Stations - North to South

Chlo

roph

yll R

ange

(ug/

L)

* Indicates data gaps greater than 15 days

Bullock Reach remains eutrophic throughout all years. North Prudence chlorophyll levels have dropped since 2006. Mt. View ranges vary, but remain below 20 ug/L.Data is grouped over 5 years to account for inter-annual variability and several years are examined during assessments.

Page 13: 2014 Dissolved Oxygen Assessment CHRP Meeting December 17, 2014 Heather Stoffel.

Conclusions

• 2014 was a “good year” (drier and cooler than average).

• NP appears to be showing a downward trend in oxygen exceedences and chlorophyll levels.

• MV may also be showing a downward trend in oxygen, but further analysis is needed.

• MH needs further examination. It is possible hypoxia is increasing in this area.