Cooks Bay (DNR ID: 27-0133-05)
Sampling Location GPS Coordinates: Surface Area: 362 acres Max. Depth: 43 ft
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Cooks Bay is located in Mound. Head east on Minnetonka Blvd, and turn right on Co Rd 101 S. Turn right MN-7 and turn right at Hwy 44. Next turn right at Bartlett Blvd and continue until Bay Park, which is on the right side of the road. Public boat access is available.
Lake Minnetonka is a class 2B lake protected for aquatic life and recreation. Water quality information is available beginning in 1996. MCWD staff have been monitoring the site on Cooks Bay 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 above the bottom were collected with a Van Doran water sampler. Surface sample were analyzed for total phosphorus (TP), soluble reactive phosphorus (SRP), total nitrogen (TN), where the bottom 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) | 1.4 - 2.5 | 1.9 | 51 | B |
| Surface TP (µg/L) | 21 - 38 | 29.4 | 53 | B |
| Chlorophyll-a (µg/L) | 9 - 21 | 13.3 | 56 | B |
| Overall Score | 53 | B |
The following summary refers to Figure 3.9 (a-d).
- Secchi disk depth increased from 2.3 m to 4.1 m by the middle of May. From early June
to late July, secchi disk depth decreased from 4.1 m to 1.5 m. The rest of the season,
water transparency fluctuated between 1.4 m and 2.2 m until early October (2.7 m)
(standard > 1.4 m). - Chlorophyll-a concentrations gradually increased throughout the season. From late April
to the middle of May concentrations decreased from 7 μg/L to 4.5 μg/L, then increased to
15 μg/L by the middle of July. Chlorophyll-a concentrations fluctuated for the rest of the
season peaking at 21 μg/L in late September (standard < 14 μg/L). - Surface TP concentrations decreased from 41 μg/L to 26 μg/L from late April to early
May. TP concentrations fluctuated between 21 μg/L and 38 μg/L throughout the rest of
the season (standard < 40 μg/L). Surface SRP were below detection limit (< 0.005 μg/L)
for the entire season. - Bottom TP concentrations gradually increased from late April to the late June, then from
the middle of July to late September concentrations increased from 282 μg/L to 601
μg/L. TP concentrations declined to 30 μg/L by early October. Bottom SRP
concentrations gradually increased from late April to early September with the highest
concentration occurring in the middle of August (197 μg/L). From the middle of
September to early October, SRP concentrations declined from 172 μg/L to < 0.005 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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