Minnesota's 2012 National Lakes Assessment was led by MPCA's Water ... Pictures on front cover are examples of lakes sampled in this 150-lake survey effort.
National Lakes Assessment 2012 Water chemistry, lake morphometry, and watershed characteristics of Minnesota’s 2012 NLA lakes This is part of a series based on Minnesota’s participation in the United States Environmental Protection Agency’s 2012 National Lakes Assessment
January 2016
Authors Steve Heiskary, Environmental Analysis and Outcomes Division
Report review Jesse Anderson Pam Anderson Lee Engel
Contributors/acknowledgements Minnesota’s 2012 National Lakes Assessment was led by MPCA’s Water Quality Monitoring Unit. A total of 150 lakes were sampled during summer 2012 in this effort. Team leads for the survey, which included responsibility for field reconnaissance, assembling and purchasing needed equipment, office logistics, and sampling of the lakes was led by Pam Anderson, Jesse Anderson, Kelly O’Hara, Lee Engel, Dereck Richter, and Steve Heiskary. Other staff assisting with sampling included: Amy Garcia, Courtney Ahlers-Nelson, Mike Kennedy and Andrew Swanson. Student workers Will Long and Ben Larson also assisted with the sampling. In addition to MPCA staff, Minnesota Department of Natural Resources, U.S. Forest Service, Red Lake Band of the Chippewa and White Earth Band of the Ojibwe natural resources staff were instrumental in support of sampling and reconnaissance for many of the lakes in this survey. Pictures on front cover are examples of lakes sampled in this 150-lake survey effort.
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Minnesota Pollution Control Agency 520 Lafayette Road North | Saint Paul, MN 55155-4194 | www.pca.state.mn.us | 651-296-6300 Toll free 800-657-3864 | TTY 651-282-5332 This report is available in alternative formats upon request, and online at www.pca.state.mn.us . Document number: wq-nlap1-14
Contents Executive summary ............................................................................................................................1 Introduction ......................................................................................................................................2 National Lakes Assessment overview and lake selection for 2012................................................................... 2 Minnesota’s NLA overview and report focus.................................................................................................... 3
Background .......................................................................................................................................4 Climate comparison: summer 2007 and 2012.................................................................................................. 4
Methods ............................................................................................................................................8 Comparison of EPA and MDH Data .................................................................................................................. 9
Results and discussion......................................................................................................................11 Description of the population of lakes and morphometry....................................................................... 12 Description of lake watershed areas and land use composition .............................................................. 14 Water chemistry and physical characteristics ....................................................................................... 20 Field measurements: temperature, dissolved oxygen (DO), and DO saturation ............................................ 22 Nutrients and Trophic Status Indicators ......................................................................................................... 26 Organic carbon and color ............................................................................................................................... 34 Ion Chemistry.................................................................................................................................................. 35 Applications of NLA data ..................................................................................................................... 44 1. Trends and variability in lake condition based on 2007 and 2012 ............................................................. 44 2. Regional patterns, interrelationships, and watershed and lake morphometry as they influence lake condition and chemistry .......................................................................................................... 48
Summary and conclusions ................................................................................................................54 References.......................................................................................................................................56 Appendix .........................................................................................................................................57
List of tables Table 1. Land use composition (percent of watershed) based on a) 2012 NLA lake watersheds and Level 3 aggregated ecoregions and b) ecoregion reference lakes and Level 3 ecoregions.. ...................... 16 Table 2. Statewide summary of 2012 NLA data. Includes: 10th, 25th, 50th, 75th, and 90th (unweighted) percentiles for each parameter. ................................................................................................................. 21 Table 3. Ecoregion reference lake database summary. .............................................................................. 22 Table 4. Comparison of un-weighted mean concentrations for 2012 re-sample lakes.............................. 45 Table 5. Comparison of unweighted percentile distributions of select parameters from 2007 and 2012.. .......................................................................................................................................... 48
List of figures Figure 1. Minnesota’s 2012 NLA lakes overlain on Level 3 ecoregion map.................................................. 4 Figure 2. Summer normal mean temperatures and monthly mean temperatures from select sites in 2007 and 2012 and summaries for select locations. .................................................................................... 5 Figure 3. Water year precipitation and departure for 2007 and 2012. ........................................................ 6 Figure 4. Drought monitor map for Minnesota, September 2012. .............................................................. 7 Figure 5. Lakes that were dropped from the survey. Dry implies either completely dry or too shallow ( 1 µg/L. ........................................................................................................................ 30 Figure 23. Secchi transparency CDF and plots by region. Trophic categories as follows: oligo > 3.5 m, meso 2.0-3.5 m, eutrophic 0.7-2.0 m, and hypereutrophic ) indicates greater than values included in these calculations.] ............................................................................................... 30 Figure 24. Total nitrogen (TN) CDF and maps by ecoregion. Trophic categories as follows: 2.0 mg/L hypereutrophic.............................. 32 Figure 25. TN: TP ratios for NLA lakes. CDF and maps by ecoregion. Categories: 17:1 P-limited. Two high values (281:1 & 480:1) excluded from CDF. .......... 32 Figure 26. Dissolved ortho-phosphorus relative percent and maps ecoregion. Categories used: ≤5 below RL, 6-20 moderate, and >20 µg/L high. ....................................................................................... 33 Figure 27. Color distributions and regional maps. Categories as follows: 100 PCU very dark. ....................................................................................................... 34 Figure 28. Dissolved organic carbon CDF and ecoregion maps. Categories used are: 14 mg/L high. ................................................................................................................... 35 Figure 29. Conductivity regional distribution and maps. Minnesota based categories (NLA IQ range) used: 500 µmhos/cm high................................................................. 37 Figure 30. pH regional distributions and maps. Minnesota and EPA based thresholds used: 8.5 high. ..................................................................................................................... 37 Figure 31. Calcium regional distributions and maps. Minnesota-based categories used: 20 mg/L high. ......................................................................................................... 38 Figure 32. Magnesium regional distributions and maps. EPA-proposed categories used: 27 mg/L high. .................................................................................................................. 38 Figure 33. Sodium regional distributions and maps. EPA-proposed thresholds as follows: 7 mg/L high ................................................................................................................ 39 Figure 34. Potassium regional distributions and maps. EPA proposed thresholds 5 mg/L high...................................................................................................................... 40 Figure 35. Silica regional distributions and maps. EPA-proposed thresholds: 11 mg/L high. ..................................................................................................................................... 40 Figure 36. Alkalinity regional distributions and maps. EPA and MN-based thresholds used: 150 mg/L hard. ..................................................................................................... 42 Figure 37. Sulfate regional distributions and maps. Minnesota-based thresholds: 50 mg/L high. Values below 1 mg/L RL treated as 1 mg/L for this analysis. CDF scaled to 100 mg/L was included to allow for resolution for NF and ETF regions................................................. 43 Figure 38. Chloride regional distributions and maps. EPA proposed thresholds used: 25 mg/L high. Note Minnesota’s standard is 230 mg/L. .................................................. 44
Figure 39. Comparison of 2007 and 2012 measurements for select parameters. 1:1 line included for visual comparison. Charts scaled to allow resolution for majority of data. ............................................... 46 Figure 40. Comparison of color and DOC, color and Chl-a, and color and Secchi by region (measures where disk is on the bottom treated as actual measures). Color and Secchi (no regions) excludes all lakes with Secchi on bottom. ..................................................................................................................... 50 Figure 41. Quantile regression of Secchi and Color. Based on RQSSCIfit in R (tau=0.90, lambda=125; R 2009) ........................................................................................................................................................ 50 Figure 42. Total organic carbon as a function of a) DOC and b) % forest & wetland. Data sorted by ecoregion. ................................................................................................................................................... 51 Figure 43. Chlorophyll-a as a function of sample date (DATEVALUE function), by ecoregion. Sampling period ran from June 2- September 5, 2012. ............................................................................................. 51 Figure 44. TP, TN, and Chl-a relative to disturbed land use. Regression-tree (changepoint) calculated in R (rpartboot, c (0.9), type=norm). Primary (first split) in green solid and secondary in blue (dashed). .... 53 Figure 45. Chloride and percentage developed land use. Primary (first split) in green solid and secondary in blue (dashed). Note outlier value at 150 mg/L is South Lake, which receives a WWTF discharge. .................................................................................................................................................... 53
Executive summary Minnesota’s 2012 National Lakes Assessment (NLA) effort was led by the Minnesota Pollution Control Agency (MPCA) and Minnesota Department of Natural Resources (MDNR). Numerous other collaborators included the U.S. Forest Service (USFS), Minnesota Department of Agriculture (MDA), and U.S. Geological Survey. USFS staff assisted with the sampling of remote lakes in the Boundary Waters Canoe Area Wilderness (BWCAW) and the National Park Service assisted in Voyageurs National Park. The Red Lake Band of the Chippewa and White Earth Band of the Ojibwe provided valuable assistance for lakes that were located on their reservations. Minnesota received 42 lakes as a part of the original draw of lakes for the national survey and added 8 to allow for state-based assessment. All 50 lakes were sampled in accordance with the national (EPA) protocols, including nearshore habitat assessments. Minnesota added 100 more lakes to the survey to yield 50 lakes per aggregated Level 3 ecoregion (Northern Forests [NF], Eastern Temperate Forests [ETF], and Great Plains [GP]). These lakes were sampled for water chemistry, biology, and physical measurements at the index site, in accordance with national protocols. Summer 2012 drought led to a large number of lakes being dropped from the survey because they were dry or too shallow (1 µg/L. The aquatic invasive zebra mussel requires adequate calcium (Ca) to support shell growth. A level of ~10 mg/L is mentioned as an important threshold. On a statewide basis, about 28% of Minnesota’s lakes have Ca 0.9
2
2
63 NLA12_MN-201
EASTERN TEMPERATE F06/27/2012
16:00
9.0
119.9 210.0
8.3
333
26.1
1.6
64 NLA12_MN-202
NORTHERN FORESTS 08/01/2012
11:00
7.5
95.1 434.0
7.3
38
24.3
>2.2
1
1
65 NLA12_MN-203
GREAT PLAINS
07/23/2012
15:00
18.5
257.9 133.0
8.7
948
30.9
0.2
4
4
66 NLA12_MN-204
GREAT PLAINS
07/11/2012
15:30
11.5
151.1 267.0
9.0
293
28.4
0.3
2
3
67 NLA12_MN-205
EASTERN TEMPERATE F07/23/2012
17:30
12.9
173.0 111.0
9.1
243
28.7
1.0
2
1
68 NLA12_MN-206
NORTHERN FORESTS 06/26/2012
14:30
11.9
316.0
8.2
178
24.2
2
2
69 NLA12_MN-207
EASTERN TEMPERATE F08/01/2012
15:30
10.1
136.1 322.0
9.1
424
27.7
0.6
4
4
70 NLA12_MN-211
EASTERN TEMPERATE F08/07/2012
10:30
8.8
113.2 252.0
9.1
188
25.1
>1.1
2
2
71 NLA12_MN-212
EASTERN TEMPERATE F08/07/2012
15:00
11.6
157.4 198.0
180
28.4
>1.6
2
2
72 NLA12_MN-213A EASTERN TEMPERATE F07/31/2012
15:30
11.5
148.4 214.0
8.9
652
27.0
0.5
3
3
73 NLA12_MN-214
NORTHERN FORESTS 08/07/2012
11:00
7.2
87.7 400.0
7.8
68
22.6
1.8
3
1
74 NLA12_MN-215
GREAT PLAINS
07/09/2012
14:00
10.2
140.5 189.0
9.0
555
30.5
0.4
4
4
75 NLA12_MN-217
NORTHERN FORESTS 06/27/2012
15:00
9.9
129.5 191.0
9.1
76
25.1
0.8
3
4
393
7.7
54
23.4
1.8
2
1
76 NLA12_MN-218A NORTHERN FORESTS 7/30/2012
7.7
97.0
77 NLA12_MN-219
GREAT PLAINS
08/20/2012
14:00
16.8
209.7 357.0
9.0
822
25.3
0.2
5
5
78 NLA12_MN-220
GREAT PLAINS
07/17/2012
14:00
11.2
152.7 179.0
9.0
701
27.9
0.2
4
4
79 NLA12_MN-221
EASTERN TEMPERATE F06/11/2012
17:00
9.8
112.9 182.0
8.6
518
21.7
2.1
2
2
80 NLA12_MN-227
EASTERN TEMPERATE F08/07/2012
13:00
8.8
118.7 297.0
7.6
39
27.8
>1.2
2
2
81 NLA12_MN-228
GREAT PLAINS
07/23/2012
12:30
14.0
195.1 66.0
9.2
492
30.8
>1
1
1
82 NLA12_MN-229A NORTHERN FORESTS 06/27/2012
09:00
7.5
93.8 283.0
7.3
57
23.3
2.8
1
1
83 NLA12_MN-233
NORTHERN FORESTS 08/09/2012
14:30
4.2
50.6 338.0
7.4
244
22.4
1.5
1
1
84 NLA12_MN-235
GREAT PLAINS
08/22/2012
11:30
10.3
123.7 308.0
9.1
746
22.5
>1.1
2
3
85 NLA12_MN-236
EASTERN TEMPERATE F07/12/2012
11:00
13.6
173.1 273.0
9.9
321
26.6
0.3
4
4
86 NLA12_MN-237
EASTERN TEMPERATE F08/09/2012
10:30
8.3
105.1 232.0
350
24.5
0.3
2
2
87 NLA12_MN-240
NORTHERN FORESTS 07/23/2012
12:00
2.5
31.5 433.0
6.2
15
26.6
1.0
4
3
88 NLA12_MN-243
NORTHERN FORESTS 08/06/2012
12:30
7.4
90.8 195.0
7.3
69
24.8
1.7
1
1
89 NLA12_MN-245
EASTERN TEMPERATE F08/08/2012
12:30
9.4
117.7 302.0
9.1
174
24.3
>1.1
1
1
90 NLA12_MN-247
GREAT PLAINS
06/13/2012
20:00
9.2
106.3 348.0
8.1
409
21.1
0.4
4
4
91 NLA12_MN-248
EASTERN TEMPERATE F08/20/2012
15:15
8.8
109.1 312.0
8.2
298
24.7
1.1
2
2
92 NLA12_MN-249
NORTHERN FORESTS 07/10/2012
17:30
13.8
179.5 195.0
8.9
212
27.4
0.7
3
3
93 NLA12_MN-250
GREAT PLAINS
08/15/2012
12:30
7.6
92.1 345.0
8.4
453
22.3
0.1
2
4
94 NLA12_MN-251
GREAT PLAINS
07/09/2012
16:00
12.0
165.9 208.0
8.9 1399
30.4
0.5
4
4
95 NLA12_MN-252
EASTERN TEMPERATE F06/12/2012
20:00
9.5
112.5 296.0
9.2
282
22.5
>2
3
3
96 NLA12_MN-253
EASTERN TEMPERATE F07/31/2012
17:45
10.4
136.2 196.0
8.7
318
27.7
0.7
3
3
97 NLA12_MN-254
NORTHERN FORESTS 08/06/2012
16:30
8.3
105.3 172.0
7.0
49
26.3
>1.1
1
1
98 NLA12_MN-255
EASTERN TEMPERATE F07/30/2012
13:45
13.9
177.9 222.0
8.7
531
26.4
0.8
4
4
99 NLA12_MN-256
NORTHERN FORESTS 07/23/2012
17:30
8.6
114.5 363.0
7.7
112
29.1
1.0
3
3
100 NLA12_MN-258
NORTHERN FORESTS 08/06/2012
12:30
7.1
88.5 335.0
8.1
164
23.8
1.5
2
2
National Lakes Assessment: 2012 • January 2016
Minnesota Pollution Control Agency 63
#
Site ID
Aggregated ecoregion
Date
Time
DO
DO-Sat ORP
pH
Cond Temp
Secchi Phys (m) Appear
Rec Suit
101 NLA12_MN-264
EASTERN TEMPERATE F08/20/2012
18:00
10.2
122.9 347.0
8.1
552
23.3
>1.2
1
2
102 NLA12_MN-265
EASTERN TEMPERATE F06/11/2012
14:30
9.4
105.2 331.0
8.5
504
19.6
0.4
4
3
103 NLA12_MN-267
GREAT PLAINS
07/23/2012
14:00
18.6
261.5 125.0
8.7 1894
31.2
0.1
4
4
104 NLA12_MN-268
GREAT PLAINS
08/15/2012
13:30
8.6
103.9 336.0
8.5
572
22.3
0.1
4
4
105 NLA12_MN-269
EASTERN TEMPERATE F07/23/2012
16:00
10.8
144.9 122.0
8.9
243
28.9
3.8
1
1
106 NLA12_MN-271
EASTERN TEMPERATE F08/20/2012
14:30
11.1
133.5 263.0
9.8
188
23.3
>1.8
2
2
107 NLA12_MN-272A NORTHERN FORESTS 06/18/2012
13:00
8.8
102.3 540.0
8.2
4
20.4
5.0
1
1
108 NLA12_MN-273
EASTERN TEMPERATE F08/09/2012
12:30
7.1
92.6 287.0
8.5
193
25.9
4.5
2
2
109 NLA12_MN-274
NORTHERN FORESTS 07/10/2012
20:15
8.5
110.4 135.0
8.0
293
27.6
3.9
1
1
110 NLA12_MN-275
EASTERN TEMPERATE F08/07/2012
09:00
7.3
92.2 329.0
6.2
100
24.7
0.8
2
2
111 NLA12_MN-276
EASTERN TEMPERATE F08/27/2012
10:00
6.6
80.4 196.0
7.7
242
23.9
1.0
2
3
112 NLA12_MN-277A GREAT PLAINS
08/02/2012
09:00
4.6
57.7 318.0
8.8
715
24.4
>1
2
2
113 NLA12_MN-280
GREAT PLAINS
08/13/2012
14:00
15.3
183.8 141.0
9.2
325
23.2
0.2
5
5
114 NLA12_MN-281
NORTHERN FORESTS 06/12/2012
17:00
11.4
130.5 369.0
8.3
288
20.7
>1
2
3
115 NLA12_MN-283
GREAT PLAINS
08/20/2012
16:00
10.7
134.9 310.0
9.4
868
25.8
>1
2
4
116 NLA12_MN-284
GREAT PLAINS
07/11/2012
13:00
13.8
182.6 344.0
8.9 1025
28.7
>1
1
1
117 NLA12_MN-287
GREAT PLAINS
08/01/2012
15:30
12.1
159.1 103.0
9.9
325
27.4
0.5
4
4
118 NLA12_MN-288
NORTHERN FORESTS 08/27/2012
13:00
8.0
97.6 450.0
7.1
23
24.0
2.0
2
1
119 NLA12_MN-290
NORTHERN FORESTS 08/09/2012
17:30
6.6
81.9 403.0
6.7
24
23.7
1.2
1
1
120 NLA12_MN-293
NORTHERN FORESTS 06/27/2012
13:00
8.5
111.5 203.0
7.7
152
25.4
>1.8
2
2
121 NLA12_MN-297
NORTHERN FORESTS 08/09/2012
11:30
7.4
90.9 335.0
8.0
216
23.3
1.5
1
1
122 NLA12_MN-299
GREAT PLAINS
08/22/2012
10:00
7.2
85.2 320.0
9.5
892
21.7
0.2
5
5
123 NLA12_MN-300
GREAT PLAINS
07/12/2012
08:00
4.7
60.5 315.0
8.7
365
27.0
0.4
2
2
124 NLA12_MN-303
GREAT PLAINS
08/02/2012
12:00
9.4
122.1 98.0
8.5
316
25.8
1.8
3
2
125 NLA12_MN-304
NORTHERN FORESTS 08/07/2012
15:00
3.6
46.3 229.0
6.3
122
25.4
1.3
1
1
126 NLA12_MN-306A NORTHERN FORESTS 07/23/2012
11:00
8.0
104.5 390.0
7.6
93
25.9
2.0
1
1
127 NLA12_MN-313
NORTHERN FORESTS 06/18/2012
17:00
9.4
108.6 502.0
8.6
250
20.3
6.0
1
1
128 NLA12_MN-315
GREAT PLAINS
07/16/2012
19:30
9.4
125.8 184.0
8.6
484
27.0
0.3
3
3
129 NLA12_MN-318
NORTHERN FORESTS 08/06/2012
15:00
9.8
122.9 166.0
7.2
22
25.9
0.9
1
1
130 NLA12_MN-320
NORTHERN FORESTS 07/23/2012
15:30
12.6
168.0 313.0
9.6
71
28.9
0.9
2
2
131 NLA12_MN-322A NORTHERN FORESTS 08/02/2012
2
11:30
7.1
91.6 396.0
8.2
216
25.3
3.7
1
132 NLA12_MN-325
GREAT PLAINS
07/19/2012
09:00
7.9
100.2 298.0
8.3
794
25.1
>1.3
2
3
133 NLA12_MN-334
NORTHERN FORESTS 06/26/2012
13:00
9.5
118.6 369.0
8.4
292
23.9
3.4
1
1
134 NLA12_MN-335
GREAT PLAINS
07/30/2012
17:30
11.8
152.1 190.0
8.8
404
26.9
0.8
4
4
135 NLA12_MN-338
NORTHERN FORESTS 07/10/2012
19:00
8.5
110.9 141.0
8.1
250
27.5
3.8
1
1
136 NLA12_MN-341
GREAT PLAINS
07/30/2012
17:30
10.3
138.0 133.0
8.9
345
28.4
1.3
2
2
137 NLA12_MN-342
NORTHERN FORESTS 07/24/2012
11:00
8.7
113.6 354.0
8.8
305
26.3
3.0
2
1
138 NLA12_MN-346
NORTHERN FORESTS 08/28/2012
14:00
8.5
102.2 403.0
7.3
9
21.6
2.4
1
1
139 NLA12_MN-367
GREAT PLAINS
07/30/2012
16:00
8.2
106.2 485.0
8.2
361
26.9
3.4
2
1
GREAT PLAINS
07/11/2012
17:30
12.0
161.1 335.0
8.7
417
29.4
0.3
2
3
GREAT PLAINS
08/21/2012
11:00
10.5
124.9 162.0
8.3
828
22.3
>1.6
2
2
142 NLA12_MN-396A GREAT PLAINS
08/20/2012
10:30
15.5
183.9 234.0
8.7
376
22.5
0.1
4
4
143 NLA12_MN-414A GREAT PLAINS
08/21/2012
16:30
11.4
138.2 201.0
8.2
288
23.1
0.5
3
3
144 NLA12_MN-415
GREAT PLAINS
08/02/2012
09:00
8.5
108.7 152.0
9.2
237
25.0
1.1
3
3
145 NLA12_MN-420
GREAT PLAINS
08/21/2012
10:00
10.8
126.1 175.0
8.8 1018
21.4
1.2
3
3
146 NLA12_MN-427A GREAT PLAINS
08/21/2012
08:30
7.5
87.6 230.0
7.8 1154
21.1
0.3
3
4
147 NLA12_MN-443
GREAT PLAINS
08/20/2012
16:15
10.1
120.4 157.0
8.3
719
23.0
2.7
3
3
148 NLA12_MN-444A GREAT PLAINS
08/20/2012
14:00
10.2
121.0 196.0
8.3
652
22.8
0.2
3
3
149 NLA12_MN-475
09/05/2012
14:00
9.2
110.7 19.0
8.6 1193
22.2
0.2
4
4
140 NLA12_MN-378 141 NLA12_MN-395
GREAT PLAINS
National Lakes Assessment: 2012 • January 2016
Minnesota Pollution Control Agency 64
NLA 2012 lakes: nutrient and chlorophyll data #
Site ID
Total P (ug/L)
DOP (mg/L)
Chl-a (μg/L)
Pheo-a Microcystin TKN (ug/L) (ug/L) (mg/L)
Total N NO3 (mg/L) (mg N/L)
NH3-N (mg/L)
1 NLA12_MN-101
22 < 0.005
8.0
1.7
< 0.15
0.64
0.52
0.002
0.011
2 NLA12_MN-102
44 < 0.005
5.7
1.7
0.26
0.58
0.50
0.004
0.025
3 NLA12_MN-103
36
0.69
0.008
0.019
4 NLA12_MN-104
38 < 0.005
1.8
0.66
0.002
0.017
5 NLA12_MN-105
26
5.5
0.40
0.016
0.074
6 NLA12_MN-106
48 < 0.005
2.9
< 0.53
< 0.15
0.60
0.63
0.000
0.011
7 NLA12_MN-107
98
0.012
41.8
2.0
< 0.15
1.67
4.06
2.795
0.032
8 NLA12_MN-108
21
3.5
