West Arm (DNR ID: 27-0133-14)
Sampling Location GPS Coordinates: Surface Area: 577 acres Max. Depth: 44 ft
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West Arm is located near the city of Spring Park. Head east on Minnetonka Blvd, and turn left on Co Rd 101 S. Turn right at Grays Bay Blvd and continue on Bushaway Rd. Turn left on Eastman Ln/Shady Ln, then a slight right at E Circle Dr. Next take a slight left at Lake St. E. Turn left at Ferndale Rd S and continue on Shoreline Dr. Turn right at Northshore Dr. Public access is available at the North Arm boat access located off of Northshore Drive two miles west from Shoreline Drive at Smiths Bay.
West Arm 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 West Arm 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) | 0.4 - 1.8 | 1.0 | 61 | C |
| Surface TP (µg/L) | 46 - 88 | 70.1 | 65 | D |
| Chlorophyll-a (µg/L) | 18 - 86 | 43.8 | 68 | C |
| Overall Score | 65 | C- |
The following summary refers to Figure 3.53 (a-d).
- Secchi disk depth increased to 4.5 m by early May and then decreased to 0.4 m by early August. Secchi disk depth increased to 1.8 m by late September, and declined to 1.0 m by the end of the season (standard > 1.4 m).
- Chlorophyll-a concentrations increased to 86 μg/L from early May to early August. Concentrations declined for the remainder of the season ranging from 30 μg/L to 36 μg/L (standard < 14 μg/L).
- There was an overall increase with surface TP concentrations throughout the season as concentrations fluctuated between 46 μg/L and 88 μg/L (standard < 40 μg/L). Surface SRP concentrations were below detection limit (< 0.005 μg/L) except from late April to late May, early July, and from early September to early October.
- There was an overall increase in both bottom TP and SRP concentrations from late April to early July. The maximum concentration for TP was 452 μg/L and SRP was 386 μg/L. From late July to late September both nutrients fluctuated between 154 μg/L and 347 μg/L. By the early October, both nutrient concentrations declined below 70 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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