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.
Currently not available.
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. Water samples were collected at one meter below the water surface and one meter from the bottom. Surface and bottom sample parameters analyzed included total phosphorus (TP), total dissolved phosphorus (TDP), soluble reactive phosphorus (SRP), total nitrogen (TN), total dissolved nitrogen (TDN), nitrate/nitrite (NO3/NO2) and ammonia (NH4). Surface concentrations of chlorophyll-a were also analyzed and measurements of Secchi disc depth were recorded.
| 2008 Summer Water Quality Summary |
| Parameters | Range | Mean | TSI Value | Lake Grade |
| Months | June - Sept. | May - Sept. | ||
| Secchi Depth (m) | 2.9 - 4.5 | 3.5 | 42 | A |
| Surface TP (µg/L) | 14 - 20 | 15.8 | 44 | A |
| Chlorophyll-a (µg/L) | 3 - 6 | 4.4 | 45 | A |
| Overall Score | 44 | A |
The following summary refers to Figure 3.15 (a-d).
- Throughout the season there was a general increase in secchi disk depth. From late April to late May secchi disked was about 2.6 m. Secchi disked fluctuated between 2.9 m and 3.9 m from June to September. In late September, secchi disk depth reached a maximum for the season at 4.5 m then declined to 3.9 m in October (standard > 1.2 m).
- Chlorophyll-a concentrations were below the standard for the entire season (< 15 µg/L). Concentrations were 8 µg/L for the beginning of the season then declined to 4 µg/L by early June. Chlorophyll-a concentrations increased slightly from June to October. The maximum concentration was 6 µg/L occurring in mid- September.
- Surface TP concentrations were below the standard limit for the season (< 40 µg/L). From late April to late May, early September and October, concentrations were ranged from 20 µg/L and 24 µg/L. TP concentrations were between 14 µg/L and 18 µg/L for rest of the season. Surface SRP were below detection limit (< 0.005 µg/L) except in middle of May when the SRP concentration was 13 µg/L.
- Bottom TP concentrations were greater than 50 µg/L in late May, late July and middle of August while the remainder of the season concentrations were less than 40 µg/L. Bottom SRP concentrations were below detection limit (< 0.005 µg/L) except in the middle and end of May and late July.
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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