Lower Lake North (Lake Minnetonka Upper) (DNR ID: 27-0133-02)
Sampling Location - GPS Coordinates: Surface Area: 1008 acres Max. Depth: 73 ft
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Lower Lake North is located near the cities of Orono, Deephaven, and Minnetonka Beach on Lake Minnetonka. Head west on Minnetonka Blvd toward Maplewood Rd, and turn left to stay on Minnetonka Blvd. Next turn right to stay on Minnetonka Blvd. Public boat launch is on the right. Lower Lake North is adjacent to Carsons Bay.
Lower Lake North is on Lake Minnetonka which is a class 2B lake protected for aquatic life and recreation. Water quality information is available beginning in 1997. MCWD staff have been monitoring the site on Lower Lake North on a bi-weekly basis from the time of ice out (April) to the time of fall mixing (mid-October) since 2006.
See Previous Reports.
Monitoring season started in late April and ended in late October. A YSI multi-probe sonde was used to measure dissolved oxygen (DO), temperature (oC), pH, and specific conductivity (µS/cm) at each meter depth from the water surface to the bottom. Additionally, water samples were collected within the first two meters of the surface with a 2-meter composite sampling tube. Samples one meter below the thermocline and one meter above the bottom were collected with a Van Doran water sampler. Surface samples were analyzed for total phosphorus (TP), soluble reactive phosphorus (SRP), total nitrogen (TN), where bottom and thermocline samples were analyzed for TP and SRP. Surface concentrations of chlorophyll-a were also analyzed and measurements of Secchi disc depth were recorded. .
| 2009 Summer Water Quality Summary |
| Parameters | Range | Mean | TSI Value | Lake Grade |
| Months | June - Sept. | May - Sept. | ||
| Secchi Depth (m) | 2.9 - 4.9 | 3.6 | 41 | A |
| Surface TP (µg/L) | 12 - 23 | 15.0 | 43 | A |
| Chlorophyll-a (µg/L) | 1 - 5 | 3.5 | 43 | A |
| Overall Score | 43 | A |
The following summary refers to Figure 3.27 (a-d).
- Secchi disk depth was above the standard limit (> 1.4 m) for the entire season. From late
April to early June, secchi disk depth ranged between 3.9 m and 4.1 m, and then
decreased to 2.9 m by the middle of July. By early September, secchi disk depth
increased to 4.9 m, and decreased again to 4.1 m by the end of the season. - Chlorophyll-a concentrations fluctuated between 1 μg/L and 6 μg/L (standard < 14 μg/L).
The lowest concentration of chlorophyll-a occurred in late July, while the highest
concentration of chlorophyll-a occurred in late May and early October. - Surface TP concentrations fluctuated between 13 μg/L and 27 μg/L from late April to
early June. TP concentrations then declined in late June and ranged between 12 μg/L and
17 μg/L until autumn. In early October, TP concentrations increased slightly to 20 μg/L.
Surface SRP were below detection limit (< 0.005 μg/L) except in early October (5 μg/L). - Both bottom TP and SRP concentrations were less than 45 μg/L from late April to early
July. From the middle of July to early September both TP and SRP concentrations
increased, and then both nutrients declined at the end of the season. Highest
concentration of TP was 389 μg/L and highest concentration of SRP was 241 μg/L.
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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