Diamond Lake (DNR ID: 27-0022-00)
Sampling Location - GPS Coordinates: 44.9006 N, -93.2691 W Surface Area: 41 acres Max Depth: 6.9 ft
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Diamond Lake located in the city of Minneapolis. Go east on Minnetonka Blvd and take a left on McGinty Rd W. Turn right to merge onto I-494 S. Take exit 5A to merge onto 1-35W N toward Minneapolis. Take exit 12B toward Diamond Lake Rd, merge onto 2nd Ave S. Turn right at E. Diamond Lake Rd towards the lake.
Diamond Lake is a small, shallow water body classified as a Type 5 wetland and surrounded by residential neighborhoods and parkland. Water quality data is available back to 1986. Currently Minneapolis Park and Recreation Board (MPRB) staff monitor the lake on a bi-weekly basis and send MCWD the raw data each fall.
Before development, the lake/wetland would dry up during the summer months and become a marsh. MPRB received Diamond Lake and surrounding park areas between 1926 and 1936. The city of Minneapolis installed storm sewers in 1940, and by the next year, 800 acres of the watershed were draining into the lake causing drastic fluctuations in the water elevation. From 1942-1960s, several construction projects around and on the lake directed runoff into the lake and also redirected water from the northeast shore to Minnehaha Creek. In 1991, the MPRB placed a weir at 822 ft at the outlet, raising the water level to re-establish aquatic plants and restore important wildlife habitat that the lake could not support in previous years (MDNR, 1953; MPRB, 2006).
Monitoring season started in early May and ended in late October by MPRB. Hydrolab mini-sonde 5 multi-probe measured dissolved oxygen (DO), temperature (oC), pH, and specific conductivity (µS/cm) at each meter depth from the water surface to the bottom. Surface water samples were a composite of the first two meters below the surface. Surface sample parameters analyzed are extensive, MCWD is concerned with total phosphorus (TP), total nitrogen (TN), and soluble reactive phosphorus (SRP). 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) | 0.2 - 0.4 |
0.3 |
77 |
F |
| Surface TP (µg/L) | 135 - 205 |
165.7 |
78 |
F |
| Chlorophyll-a (µg/L) | 27.9 - 72 |
49.1 |
69 |
C |
| Overall Score | 74 |
D- |
The following summary refers to Figure 2.7 (a-c).
- Secchi disk depth decreased from 0.8 m to 0.6 m by early May. From June to October, secchi disk depth ranged between 0.20 m to 0.52 m (standard > 1.2 m).
- Chlorophyll-a concentrations fluctuated between 21.2 µg/L and 59.2 µg/L until August when concentrations increased to 72 µg/L. From September to October, chlorophyll-a concentrations were less than 45.9 µg/L (standard < 15 µg/L).
- Surface TP concentrations increased from 93 µg/L to 205 µg/L by early June and then increased to 201 µg/L by early July. The rest of the season there was an overall decrease in TP concentrations although concentrations remained above the standard limit (< 40 µg/L). Surface SRP concentrations peaked at 17 µg/L in late June and then remained below 10 µg/L for the rest of the season.
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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