2014 Dissolved Oxygen Assessment

CHRP MeetingJuly 7, 2015

Heather Stoffel

Data from 5 rivers that discharge into the Providence River Normalized to the 10 year seasonal total average

-1.5E+08

-1.0E+08

-5.0E+07

0.0E+00

5.0E+07

1.0E+08

1.5E+08

2.0E+08

2.5E+08

3.0E+08

Providence River Seasonal Total Flow Fl

ow (m

ᵌ/da

y)

PD BR CP NP GB SR MV QP PP MH0

10

20

30

40

50

60

70

80

Exceedences During Dry Years

2002

2004

2005

2007

2010

2012

2014

RID

OCS

Day

s

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

20

40

60

80

100

120

Exceedences During Wet Years

2001200320062008200920112013

RID

OCS

Day

s

Seasonal Cumulative River Flow from the Blackstone River

2001

2002

2003

2004

2005

2006

2007

2008

2009

2010

2011

2012

2013

2014

2015

0.0E+00

5.0E+07

1.0E+08

1.5E+08

2.0E+08

2.5E+08

3.0E+08

Blackstone River Flows SeptAugJulyJune

FL

OW

(s

ea

so

na

l c

um

. m

ᵌ./d

ay

)

Influences on River Flow during Wet Years

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

1

2

3

4

5

6

7

8Number of Extreme Flow Days from Blackstone River

Sept Aug

July June

Year

Num

ber o

f Day

s >3

St D

ev.

over

Dai

ly M

ean

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 low oxygen, but further analysis is needed.

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