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2005 PRW Dissolved Oxygen Data (in percent saturation)

NOTE: These results are preliminary pending a quality control review of data transfer procedures.

Site ID	5/21/2005	6/4/2005	6/18/2005	7/2/2005	7/16/2005	7/30/2005	8/13/2005	8/27/2005	Max	Min	Avg
P200	102.29	-	100.03	92.60	84.29	86.95	87.53	65.70	102.29	65.70	88.49
P170	100.28	71.40	95.01	87.72	82.92	82.05	85.19	83.95	100.28	71.40	86.06
P160	99.04	71.68	98.08	92.65	81.73	86.16	81.56	93.30	99.04	71.68	88.03
P150	102.76	69.22	100.72	91.49	74.14	83.50	83.74	71.13	102.76	69.22	84.59
P135	97.45	70.17	98.85	88.29	89.93	84.71	83.74	90.93	98.85	70.17	88.01
P110	100.84	66.34	97.81	87.61	82.92	93.76	85.19	88.83	100.84	66.34	87.91
P089	100.12	67.71	108.29	87.83	83.93	90.04	91.25	73.44	108.29	67.71	87.83
P080	-	71.82	95.48	89.89	87.20	90.28	78.66	85.33	95.48	71.82	85.52
P065	94.86	69.63	-	88.80	81.37	86.40	77.93	85.55	94.86	69.63	83.51
P055	99.03	70.72	-	89.89	93.84	92.42	88.10	90.35	99.03	70.72	89.19
P050	-	-	-	-	-	86.24	88.10	87.38	88.10	86.24	87.24
P030	95.76	69.49	94.43	89.26	85.10	87.67	85.19	89.84	95.76	69.49	87.09
P020	97.40	71.13	97.50	89.48	82.20	92.21	81.32	85.45	97.50	71.13	87.09
P010	99.32	-	-	-	-	-	-	75.25	99.32	75.25	87.29
OB010	47.52	30.64	51.63	45.22	41.18	37.46	40.35	49.73	51.63	30.64	42.97
BB010	83.43	-	77.44	71.80	67.39	-	68.45	65.05	83.43	65.05	72.26
DB010	98.20	68.67	95.70	84.93	77.21	88.65	65.96	90.02	98.20	65.96	83.66
PL040	85.61	56.49	78.01	66.55	80.09	69.95	72.28	65.97	85.61	56.49	71.87
PL030	92.44	59.64	91.63	72.04	79.41	84.69	82.64	85.10	92.44	59.64	80.95
PL020	94.72	60.19	92.62	85.35	79.85	84.25	78.75	80.50	94.72	60.19	82.03
PL010	87.72	60.32	89.85	73.94	80.87	82.91	83.60	85.35	89.85	60.32	80.57
BL010	92.86	61.15	92.36	-	-	72.67	58.29	-	92.86	58.29	75.47
CW020	87.42	57.32	75.72	78.43	65.11	72.23	51.03	61.40	87.42	51.03	68.58
CW010	88.33	57.86	78.23	71.58	78.29	63.35	48.83	51.92	88.33	48.83	67.30
DG010	79.99	54.58	76.09	59.80	63.82	72.04	67.05	66.95	79.99	54.58	67.54
SA010	91.18	68.26	-	85.80	-	-	-	-	91.18	68.26	81.74
WE010	91.01	62.65	-	88.06	-	-	-	-	91.01	62.65	80.57
NBL010	-	-	-	-	-	-	-	-	-	-	-
L060	91.87	58.41	80.93	66.01	51.11	60.42	73.31	76.39	91.87	51.11	69.81
L050	81.62	51.71	82.28	75.00	-	65.97	75.68	79.25	82.28	51.71	73.07
L030	-	-	-	-	-	-	-	-	-	-	-
L020	88.06	59.37	87.97	76.36	76.15	91.90	83.01	82.51	91.90	59.37	80.66
L010	89.64	61.01	82.58	74.77	69.64	90.84	70.93	68.29	90.84	61.01	75.96
IN010	80.73	50.61	-	81.13	33.40	35.45	38.49	73.20	81.13	33.40	56.14
M030	116.03	-	80.33	78.29	86.00	66.76	78.16	71.56	116.03	66.76	82.45
M010	91.55	12.17	83.06	85.31	84.52	82.81	82.93	80.59	91.55	12.17	75.37
PI020	94.86	61.69	92.42	87.94	-	-	-	-	94.86	61.69	84.23
PI010	89.53	60.32	82.21	78.80	-	-	-	-	89.53	60.32	77.72
TA040	-	-	-	-	-	-	-	-	-	-	-
TA010	82.74	58.14	-	77.60	-	-	58.91	65.04	82.74	58.14	68.49

WHAT DO THESE RESULTS MEAN?

The State Legislature has established statutes that classify Maine surface waters on the basis of water quality standards and intended uses. The Maine Department of Environmental Protection is charged with ensuring that these standards are met for all surface waters in the State. The classification scheme and standards for dissolved oxygen (DO) are as follows:

· Class A: suitable for drinking (after disinfection), swimming and fishing
· Class B: suitable for drinking (after treatment), swimming and fishing
· Class C: suitable for drinking (after treatment), swimming and fishing

The main stem of the Presumpscot River is Class A from the Eel Weir Dam to its confluence with the Pleasant River (just below sample site P150); Class B from the Pleasant River to the Saccarappa Dam (just below sample site P060); and Class C from the Saccarappa Dam to the estuary in Falmouth (just below the former site of the Smelt Hill Dam).

Dissolved Oxygen Standards
· Class A and B: not less than 7 parts per million (ppm) or 75% of saturation, whichever is higher
· Class C: not less than 5 ppm or 60% of saturation, whichever is higher

Class A or B sample sites are considered to be in violation of the State's water quality standards if the DO results for those sites are less than 7 parts per million. For Class C sample sites, the DO cannot be lower than 5 parts per million.

DO levels are considered the most important and commonly employed measurement of water quality and indicator of a water body's ability to support desirable aquatic life. The ideal DO level for fish is between 7 and 9 ppm; most fish cannot survive at levels below 3 ppm of DO. One of the most critical factors affecting DO concentration is temperature, which in turn is significantly affected by solar radiation. Waters with higher temperatures hold less DO. Temperature increases can be caused by a lack of mixing (stagnant water heats up more easily than moving water) and turbidity from sediments that absorb solar heat. Organic wastes also decrease DO through bacterial decomposition (bacteria use oxygen to "eat" organics). Finally, nutrients (especially phosphorus in fresh water) decrease DO by increasing plant and algal growth, which use oxygen in the process of photosynthesis.

What can be done to improve DO levels in the Presumpscot and its tributaries? According to the DEP, the most significant factor adversely affecting DO along the main stem is impoundment from dams. While dam removal is a controversial issue, there is little doubt that a free flowing river will generally have higher DO levels than a stagnant impoundment. Another significant detrimental influence on DO level originates from nonpoint source pollution (NPS). Reducing soil erosion and nutrient and organic runoff would result in corresponding improvements to DO levels. Providing more opportunities for water movement and mixing would also help to increase DO concentrations.

Key to PRW Abbreviations: P = Main stem of Presumpscot River, BB = Baker Brook, BL = Black Brook, CW = Colley Wright Brook, DG = Douglas Brook, DB = Ditch Brook, IN = Inkhorn Brook, L = Little River, M = Mill Brook, N = Nason Brook, OB = Otter Brook, PI = Piscataqua River (not the same as one at ME-NH border), PL = Pleasant River, TA = Tannery Brook.

The "% complete" column indicates the number of samples actually collected compared to the number of samples intended for collection. PRW has 8 sampling events per season, so if only 4 samples were collected for the season the completion rate would be 50%.