Grays Bay (DNR ID: 27-0133-01)
Sampling Location GPS Coordinates: Surface Area: 207 acres Max. Depth: 28 ft
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Grays Bay is located near the cities of Woodland, Wayzata and Minnetonka. Head east on Minnetonka Blvd, and turn left on Co Rd 101 S. Turn right at Grays Bay Blvd and enter the Grays Bay Marina and public access on the left side of the road.
Grays Bay is the last bay on the lake before the outlet to Minnehaha Creek and is adjacent to Wayzata Bay. Lake Minnetonka is a class 2B lake protected for aquatic life and recreation. Water quality information is available since 2004. MCWD staff have been monitoring the site on Grays 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 - 3.1 | 2.2 | 49 | B |
| Surface TP (µg/L) | 21 - 29 | 24.0 | 50 | B |
| Chlorophyll-a (µg/L) | 4 - 8 | 6.9 | 50 | A |
| Overall Score | 49 | B+ |
The following summary refers to Figure 3.15 (a-d).
- Throughout the season there was a general increase in secchi disk depth. Secchi disk
depth fluctuated between 2.6 m and 3.1 m from late April to the middle of July. Secchi
disk depth decreased to 1.9 m in late July, and then fluctuated between 1.4 m and 1.7 m
until early October. (standard > 1.4 m). - Chlorophyll-a concentrations were below the standard for the entire season (< 14 μg/L).
Concentrations were between 3 μg/L and 4 μg/L for the beginning of the season then
increased to 8μg/L by late June. In early September to the end of the season, chlorophylla
concentrations slightly declined to 7 μg/L. - Surface TP concentrations were below the standard limit for the season (< 40 μg/L). TP
concentrations ranged from 20 μg/L and 29 μg/L. Surface SRP were below detection
limit (< 0.005 μg/L) except in late August (6 μg/L) and early October (5 μg/L). - Bottom TP concentrations gradually increased throughout the season ranging between 16
μg/L and 41 μg/L. Bottom SRP concentrations were below detection limit
(< 0.005 μg/L) except from late June to late July and late August to early September.
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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