Data period: through 2022
Use the tabs below to view the different datasets.
________________________________________________________________________________________________________________
Secchi
Transparency
Secchi Disk Transparency
Plots
Temperature
& Oxygen
Profiles
Temperature & Dissolved Oxygen
Profiles
Most recent late summer (Aug. 1 -
Sept. 7) temperature and dissolved oxygen profile plots
Temperature and Dissolved Oxygen
Profile Data
Late summer only (Aug. 1 -
Sept. 7); limited to eight most recent profiles
Units: Temperature (TEMP) = °C; Dissolved
Oxygen (DO) = mg/L
|
|
1974-09-09
|
1981-08-19
|
1986-08-26
|
1997-08-12
|
1999-08-16
|
2002-08-20
|
2016-08-22
|
|
Depth (m)
|
TEMP
|
DO
|
TEMP
|
DO
|
TEMP
|
DO
|
TEMP
|
DO
|
TEMP
|
DO
|
TEMP
|
DO
|
TEMP
|
DO
|
|
0
|
21
|
8.6
|
24
|
7.5
|
21
|
8.2
|
21
|
8.0
|
18
|
8.8
|
19
|
9.0
|
18
|
8.6
|
|
1
|
21
|
8.6
|
24
|
8.2
|
21
|
8.2
|
21
|
7.9
|
18
|
8.6
|
18
|
8.8
|
|
|
|
2
|
21
|
8.6
|
24
|
8.0
|
21
|
8.1
|
21
|
7.8
|
17
|
8.6
|
18
|
8.8
|
17
|
8.7
|
|
3
|
21
|
8.5
|
24
|
8.0
|
21
|
8.0
|
21
|
7.7
|
16
|
8.7
|
17
|
8.5
|
17
|
8.7
|
|
4
|
21
|
8.5
|
23
|
7.2
|
21
|
8.0
|
21
|
7.6
|
16
|
8.7
|
17
|
8.2
|
|
|
|
5
|
21
|
8.5
|
21
|
5.1
|
20
|
7.9
|
21
|
7.6
|
16
|
8.4
|
16
|
8.1
|
17
|
8.0
|
|
6
|
21
|
8.5
|
21
|
4.8
|
20
|
7.6
|
20
|
6.0
|
16
|
8.3
|
16
|
8.0
|
17
|
7.9
|
|
7
|
21
|
8.0
|
|
|
|
|
|
|
16
|
8.2
|
16
|
7.9
|
|
|
|
8
|
21
|
7.8
|
|
|
|
|
|
|
|
|
16
|
7.9
|
|
|
Trophic &
Chemistry
Data
Trophic and Chemistry Summary
Values
See below for table legend
|
Avg Color
|
Avg Alk
|
Avg Cond
|
Avg pH
|
Avg TP EC
|
Avg TP SG
|
Avg TP BG
|
Avg TP PG
|
SDT Min
|
SDT Avg
|
SDT Max
|
Chl Min
|
Chl Avg
|
Chl Max
|
|
27
|
21
|
56
|
7.3
|
16
|
11
|
11
|
4.8
|
1.7
|
3.4
|
5.4
|
0.3
|
3.1
|
7.1
|
Plot Legend: Solid color
bars = parameter ranges for most Maine lakes; horizontal thick black
line: mean value for all Maine Lakes; Striped pattern = expected range
for
Northern
Lakes; white diamonds: mean values for Portage Lake.
Trophic and Water Chemistry
Data
Table Legend:
Color: Color (SPU), Alk: Alkalinity
(mg/l CaCO3), SpCon: Specific Conductivity
(\(\mu\)S/cm), pH: pH
(standard units)
TP = Total Phosphorus (\(\mu\)g/L) – EC: Epilimnion
Core, SG: Surface Grab, BG: Bottom
Grab, PG: Profile Grab
SDT = Secchi Disk Transparency (m) –
Min: minimum value, Avg: average
value, Max: maximum value, n: number
of months with Secchi readings per year, b: number of
times Secchi disk was observed touching the bottom of the lake per
year
Chl = Chlorophyll-a (\(\mu\)g/L) – Min: minimum
value, Avg: average value, Max:
maximum value
|
Year
|
Color
|
Alk
|
Cond
|
pH
|
TP-EC
|
TP-SG
|
TP-BG
|
TP-PG
|
SDT-Min
|
SDT-Avg
|
SDT-Max
|
SDT-n
|
SDT-b
|
Chl-Min
|
Chl-Avg
|
Chl-Max
|
|
1974
|
|
22.0
|
112
|
|
|
13.1
|
|
|
2.7
|
3.0
|
3.4
|
12
|
0
|
1.7
|
2.4
|
2.9
|
|
1975
|
|
24.5
|
38
|
|
|
9.7
|
|
|
2.1
|
3.4
|
4.7
|
13
|
0
|
0.3
|
2.5
|
7.1
|
|
1976
|
|
|
|
|
12
|
|
|
|
2.5
|
3.0
|
3.7
|
11
|
0
|
0.8
|
2.8
|
6.5
|
|
1977
|
|
|
|
|
|
|
7
|
|
3.2
|
3.2
|
3.2
|
1
|
0
|
|
|
|
|
1981
|
|
28.0
|
75
|
6.9
|
19
|
|
|
|
1.9
|
2.9
|
3.4
|
11
|
0
|
4.0
|
4.0
|
4.0
|
|
1982
|
|
|
|
|
|
|
|
|
2.6
|
3.1
|
3.4
|
7
|
0
|
|
|
|
|
1986
|
|
17.0
|
52
|
|
13
|
|
|
|
3.3
|
3.3
|
3.3
|
1
|
0
|
|
|
|
|
1989
|
|
|
|
|
|
|
|
4.8
|
3.6
|
3.6
|
3.6
|
1
|
0
|
0.3
|
0.3
|
0.3
|
|
1994
|
|
|
|
|
|
|
|
|
2.8
|
3.0
|
3.3
|
5
|
0
|
|
|
|
|
1995
|
|
|
|
|
|
|
|
|
2.5
|
3.2
|
3.5
|
9
|
0
|
|
|
|
|
1996
|
|
|
|
|
|
|
|
|
1.7
|
2.9
|
3.9
|
12
|
0
|
|
|
|
|
1997
|
|
19.0
|
48
|
7.4
|
19
|
|
16
|
|
2.1
|
3.3
|
4.2
|
17
|
0
|
3.2
|
3.3
|
3.4
|
|
1998
|
|
1.8
|
5
|
|
32
|
|
|
|
2.8
|
3.4
|
4.0
|
22
|
0
|
|
|
|
|
1999
|
|
22.5
|
59
|
|
10
|
|
|
|
2.7
|
3.5
|
4.9
|
23
|
0
|
5.1
|
5.1
|
5.1
|
|
2000
|
|
|
|
|
|
|
|
|
2.6
|
3.4
|
4.0
|
14
|
0
|
|
|
|
|
2001
|
|
|
|
|
|
|
|
|
3.0
|
3.5
|
4.9
|
14
|
0
|
|
|
|
|
2002
|
31
|
25.0
|
57
|
|
9
|
|
|
|
3.0
|
3.6
|
4.6
|
12
|
0
|
4.5
|
4.5
|
4.5
|
|
2003
|
|
|
|
|
|
|
|
|
2.4
|
3.3
|
4.0
|
12
|
0
|
|
|
|
|
2004
|
|
|
|
|
|
|
|
|
2.9
|
3.3
|
3.7
|
12
|
0
|
|
|
|
|
2005
|
|
|
|
|
|
|
|
|
2.6
|
3.4
|
4.2
|
13
|
0
|
|
|
|
|
2006
|
|
|
|
|
|
|
|
|
2.8
|
3.5
|
4.0
|
18
|
0
|
|
|
|
|
2007
|
21
|
23.0
|
55
|
|
|
10.0
|
|
|
2.8
|
3.6
|
4.4
|
16
|
0
|
|
|
|
|
2008
|
|
|
|
|
|
|
|
|
2.4
|
3.1
|
3.5
|
16
|
0
|
|
|
|
|
2009
|
|
|
|
|
|
|
|
|
3.0
|
3.4
|
3.8
|
11
|
0
|
|
|
|
|
2010
|
|
|
|
|
|
|
|
|
2.6
|
3.3
|
3.9
|
13
|
0
|
|
|
|
|
2014
|
|
|
|
|
|
|
|
|
4.2
|
4.6
|
5.0
|
2
|
0
|
|
|
|
|
2015
|
|
|
|
|
|
|
|
|
3.1
|
3.2
|
3.3
|
2
|
0
|
|
|
|
|
2016
|
30
|
27.0
|
58
|
7.6
|
12
|
|
|
|
3.0
|
3.3
|
3.5
|
2
|
0
|
2.8
|
2.8
|
2.8
|
|
2017
|
|
|
|
|
|
|
|
|
3.3
|
3.4
|
3.4
|
2
|
0
|
|
|
|
|
2021
|
|
|
|
|
|
|
|
|
3.2
|
4.4
|
5.4
|
5
|
0
|
|
|
|
|
2022
|
|
|
|
|
|
|
|
|
3.5
|
3.6
|
3.6
|
3
|
0
|
|
|
|
Water
Quality
Trends
Water Quality Trends
Long-term Secchi Disk Transparency (SDT), total phosphorus (TP), and
Chlorophyll-a data are used to determine if the trophic state of a lake
may be changing. Long-term trends may be calculated if there are at
least 10 years of data collected within the last 30 years (1993-2022).
If there are at least eight years of data within the most recent 10
years, a recent trend test may be calculated as well. The results of
trend tests are presented here if there have been enough data
collected from Portage Lake for any of these three parameters.
The Maine Department of Environmental Protection uses Mann-Kendall Tau
(τ) trend tests on these data to test for significantly changing
conditions. The tau value is a measure of trend direction and magnitude.
Positive tau values indicate positive (upward) trends, negative tau
values indicate negative (downward) trends. Values further from zero
(closer to -1 or 1) indicate a stronger trend. Tau values less than -0.5
or more than 0.5 here suggest the trophic state of a lake may be
changing. Trends with p-values less than 0.05 indicate statistically
significant trends.
Click
here
to learn more about how the Maine Department of Environmental
Protection uses trend test results to evaluate lakes as part of the
Maine water quality standard review process.
Fish
List
Maine IF&W Fish Survey
Data
Fish data courtesy of the Maine
Department of Inland Fisheries & Wildlife.
Fish species observed from Portage Lake:
|
All fish images from Maine Department of Inland Fisheries & Wildlife
unless noted below
|
|
Banded Killifish:
|
iNaturalist
|
