Lake of the Isles (DNR ID: 27-0040-00)
Sampling Location - GPS Coordinates: Surface Area: 103 acres Max. Depth: 31 ft
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Lake of the Isles is located in Minneapolis. Head east on Minnetonka Blvd and turn left on Co Rd 101 S. Then turn left at Grays Bay Blvd and continue on Bushaway Rd. Turn right onto the ramp to US-12 E and keep left at the fork to continue on US-12 E. Merge onto I-394 E and take exit 8A to merge onto Dunwoody Blvd/Wayzata Blvd toward Hennepin Ave. Turn right at Emerson Ave S. and another right at Kenwood Pkwy. Next take a left at Penn Ave S. and turn right to stay on Penn Ave S. Turn left at W 21st St and then turn right at W. Lake of the Isles Pkwy towards the lake.
Lake of the Isles is a polymictic lake, occasionally stratifying and mixing throughout the summer months. Water quality data is available back to 1979. Currently, Minneapolis Park and Recreation Board (MPRB) staff monitors the lake on a bi-weekly basis and sends MCWD the raw data each fall.
Lake of the Isles was a historically a wetland complex and was named for its four enclosed islands. In 1884, the south island was removed by the Chicago, Milwaukee and St. Paul Railway to allow for the train tracks to be laid between Calhoun and Isles. MPRB, in 1886, acquired the lake and surrounding area including 67 acres of wetland and 33 acres of land. Between 1889 and 1991, the second island was removed by dredging about half a million cubic yards of material increasing the size of Lake of the Isles (MPRB, 2006).
Monitoring season started in early May and ended in late October by MPRB. Hydrolab mini-sonde 5 multi-probe measured dissolved oxygen (DO), temperature (oC), pH, and specific conductivity (µS/cm) at each meter depth from the water surface to the bottom. Surface water samples were a composite of the first two meters below the surface while bottom water samples were collected one meter from the bottom. Additional discrete samples were collected throughout the thermocline mixing zone once stratification developed. Surface sample parameters analyzed are extensive; MCWD is concerned with total phosphorus (TP), total nitrogen (TN), and soluble reactive phosphorus (SRP). Surface concentrations of chlorophyll-a were also analyzed and measurements of Secchi disc depth were recorded. Thermocline and bottom samples were analyzed for TP and SRP.
| 2008 Summer Water Quality Summary |
| Parameters | Range | Mean | TSI Value | Lake Grade |
| Months | June - Sept. | May - Sept. | ||
| Secchi Depth (m) | 0.3 - 3.2 |
1.1 |
58 |
C |
| Surface TP (µg/L) | 29 - 55 |
43.5 |
59 |
C |
| Chlorophyll-a (µg/L) | 2.8 - 48 |
25.0 |
62 |
C |
| Overall Score | 60 | C |
The following summary refers to Figure 2.17 (a-d).
- Secchi disk depth increased to 3.3 m by late May and then increased to 3.2 m by late June. Secchi disk depth declined over the rest of the season except in early August (0.95 m) and October (1.8 m) (standard > 1.2 m).
- Chlorophyll-a concentrations ranged between 2.8 µg/L and 7.8 µg/L from late April to late June. Concentrations increased to 40.3 µg/L by late July then peaked at 48 µg/L by early August (standard < 15 µg/L).
- Surface TP concentrations ranged between 29 µg/L and 55 µg/L peaking in early September (standard < 40 µg/L). Surface SRP concentrations ranged between less than 0.005 µg/L and 5 µg/L.
- Both bottom TP and SRP concentrations increased to early September (TP: 213 µg/L; SRP: 174 µg/L), then declined for the remainder of the season.
Lake Grades and Historical Monitoring Summaries
When available, previous reports are linked to applicable year. Additional lake data previous to 2007 may be available in the applicable year's hydrodata report. If you have additional questions or you are looking for specific information please contact MCWD's Water Quality Staff.
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