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.
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) | 0.4 - 2.5 | 1.0 | 60 | D |
| Surface TP (µg/L) | 46 - 101 | 67.1 | 65 | C |
| Chlorophyll-a (µg/L) | 13 - 110 | 60.0 | 71 | D |
| Overall Score | 65 | D+ |
The following summary refers to Figure 3.53 (a-d).
- Secchi disk depth increased to 2.8 m by late May and then decreased to 0.4 m by the middle of September. Secchi disk depth increased slightly (0.7 m) for the rest of the season (standard > 1.2 m).
- Chlorophyll-a concentrations decreased from 89 µg/L to 13 µg/L from late April to early June. From June to early September, concentrations increased to 110 µg/L and then declined for the rest of the season (standard < 15 µg/L).
- Surface TP concentrations decreased from 70 µg/L to 39 µg/L by late May. In general, concentrations increased over the remainder of the season. The maximum TP concentration was 119 µg/L (standard < 40 µg/L). Surface SRP concentrations were below detection limit (< 0.005 µg/L) except from late April to late May, and from late September to the middle of October.
- Bottom TP concentrations peaked four times throughout the season: early May (145 µg/L), early June (145 µg/L), late August (512 µg/L) and the middle of October (137 µg/L). Bottom SRP concentrations peaked three times throughout the season: early June (118 µg/L), late July (316 µg/L), and late August (375 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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