| Report Year: 2009 |
| Mill Creek Lake, O'Brien County |
| Summary Data Table |
| Parameter | 7/6/2009 | 6/2/2009 | 2009 | 2007 | 2006 | 2005 | 2004 | 2003 | 2002 | 2001 | 2000 |
| Lake Depth (m) | 4.5 | 4.6 | 4.6 | - | 4.5 | 4.4 | 4.6 | 4.3 | 4.4 | 4.7 | 4.5 |
| Thermocline Depth (m) | 0.7 | 2.7 | N/A | N/A | N/A | N/A | N/A | N/A | N/A | N/A | N/A |
| Secchi Disk Depth (m) | 1.3 | 2.2 | 1.8 | - | 4.5 | 1.1 | 1.7 | 1.6 | 0.7 | 1.9 | 0.8 |
| Temperature(oC) | 26.8 | 19.6 | 23.2 | - | 17.7 | 23.7 | 22.9 | 21.8 | 21.5 | 23.0 | 26.0 |
| Dissolved Oxygen (mg/L) | 15.7 | 10.2 | 12.9 | - | 11.8 | 9.3 | 9.5 | 8.9 | 8.9 | 6.8 | 10.1 |
| Dissolved Oxygen Saturation (%) | 197 | 111 | 153.8 | - | 123.5 | 109.4 | 112.4 | 99.2 | 97.9 | 73.4 | 125.5 |
| Specific Conductivity (μS/cm) | 410.0 | 480.0 | 445.0 | - | 494.7 | 496.7 | 500.4 | 496.4 | 470.4 | 476.9 | 576.1 |
| Turbidity (NTU) | 2.0 | 2.7 | 2.3 | - | 4.3 | 11.3 | 8.0 | 8.4 | 24.4 | 15.4 | 23.8 |
| Chlorophyll a (μg/L) | 8.0 | 7.0 | 7.5 | - | 1.5 | 26.3 | 10.2 | 13.2 | 48.6 | 22.5 | 16.2 |
| Total Phosphorus as P (μg/L) | 34 | 27 | 30 | - | 11 | 51 | 44 | 50 | 66 | 53 | 265 |
| SRP as P (μg/L) | - | - | - | - | 1 | 1 | 1 | 1 | 1 | - | - |
| Total Nitrogen as N (mg/L) | 1.01 | 0.93 | 0.97 | - | 3.14 | 1.61 | 2.10 | 2.10 | 2.16 | 2.33 | 1.25 |
| (Phenate)Ammonia Nitrogen (NH3 + NH4+) as N (μg/L) | 16 | 81 | 46 | - | 58 | 26 | 62 | - | - | - | - |
| (Phenate)Ammonia Nitrogen (NH3) as N (un-ionized)(μg/L) | 4.3 | 13.1 | 8.7 | - | 4.8 | 3.5 | 8.6 | - | - | - | - |
| Nitrate + Nitrite (NO3 + NO2) as N (mg/L) | 0.26 | 0.35 | 0.31 | - | 2.62 | 0.94 | 1.40 | 1.26 | 0.95 | 1.61 | 0.39 |
| TN:TP ratio | 30 | 35 | 32 | - | 294 | 35 | 49 | 46 | 36 | 106 | 6 |
| pH | 9.0 | 8.7 | 8.8 | - | 8.4 | 8.4 | 8.6 | 8.2 | 8.4 | 8.3 | 8.2 |
| Alkalinity as CaCO3 (mg/L) | 155 | 206 | 181 | - | 176 | 188 | 180 | 140 | 159 | 129 | 167 |
| Silica as Si (mg/L) | - | - | - | - | - | 2.01 | 1.41 | 1.13 | 1.89 | - | - |
| Dissolved Organic Carbon (mg/L) | 4.23 | 5.08 | 4.66 | - | 4.49 | 5.86 | 4.15 | 7.81 | 8.91 | - | - |
| Inorganic Suspended Solids (mg/L) | 2 | - | 2 | - | 1 | 5 | 7 | 5 | 4 | 3 | 5 |
| Volatile Suspended Solids (mg/L) | 11 | 5 | 8 | - | 1 | 7 | 4 | 4 | 12 | 5 | 10 |
| Total Suspended Solids (mg/L) | 13 | 5 | 9 | - | 2 | 12 | 11 | 10 | 11 | 8 | 14 |
| Carlson Trophic State Index (Secchi)* | 56 | 49 | 52 | - | 38 | 59 | 52 | 53 | 64 | 51 | 63 |
| Carlson Trophic State Index (Chl a)* | 51 | 50 | 50 | - | 35 | 63 | 53 | 56 | 69 | 61 | 58 |
| Carlson Trophic State Index (TP)* | 55 | 51 | 53 | - | 38 | 61 | 59 | 61 | 65 | 61 | 85 |
| *Index values generally range between 0 and 100, with increasing values indicating more eutrophic conditions. |