| Report Year: 2009 |
| Big Spirit Lake, Dickinson County |
| Summary Data Table |
| Parameter | 7/7/2009 | 6/3/2009 | 2009 | 2007 | 2006 | 2005 | 2004 | 2003 | 2002 | 2001 | 2000 |
| Lake Depth (m) | 5.9 | 6.1 | 6.0 | 6.1 | 6.5 | 6.3 | 6.2 | 6.2 | 6.4 | 6.9 | 6.4 |
| Thermocline Depth (m) | 3.0 | Nil | N/A | N/A | N/A | N/A | N/A | N/A | N/A | N/A | N/A |
| Secchi Disk Depth (m) | 2.1 | 3.0 | 2.5 | 1.6 | 2.5 | 2.3 | 1.5 | 1.6 | 1.9 | 4.3 | 2.0 |
| Temperature(oC) | 23.4 | 17.7 | 20.6 | 22.9 | 20.5 | 21.2 | 20.8 | 20.8 | 21.2 | 20.7 | 23.8 |
| Dissolved Oxygen (mg/L) | 10.3 | 8.7 | 9.5 | 10.2 | 9.9 | 9.0 | 9.9 | 10.7 | 8.4 | 8.9 | 7.9 |
| Dissolved Oxygen Saturation (%) | 121 | 91 | 105.8 | 119.5 | 108.7 | 100.5 | 110.8 | 119.7 | 94.1 | 99.1 | 96.0 |
| Specific Conductivity (μS/cm) | 480.0 | 460.0 | 470.0 | 464.1 | 503.6 | 488.4 | 491.4 | 462.7 | 580.0 | 547.1 | 485.6 |
| Turbidity (NTU) | 5.6 | 3.7 | 4.6 | 7.0 | 13.6 | 153.7 | 7.6 | 12.7 | 6.0 | 3.8 | 9.1 |
| Chlorophyll a (μg/L) | 4.0 | 3.0 | 3.5 | 25.8 | 5.7 | 67.9 | 11.8 | 20.6 | 8.3 | 5.9 | 4.8 |
| Total Phosphorus as P (μg/L) | 31 | 28 | 30 | 46 | 34 | 54 | 42 | 45 | 44 | 42 | 137 |
| SRP as P (μg/L) | - | - | - | 4 | 1 | - | 1 | 1 | 1 | - | - |
| Total Nitrogen as N (mg/L) | 0.79 | 0.70 | 0.75 | 1.15 | 1.25 | 1.24 | 0.86 | 1.04 | 0.95 | 1.00 | 0.78 |
| (Phenate)Ammonia Nitrogen (NH3 + NH4+) as N (μg/L) | - | 16 | 16 | 22 | 60 | 19 | 19 | - | - | - | - |
| (Phenate)Ammonia Nitrogen (NH3) as N (un-ionized)(μg/L) | - | 0.7 | 0.7 | 3.3 | 4.8 | 2.7 | 2.7 | - | - | - | - |
| Nitrate + Nitrite (NO3 + NO2) as N (mg/L) | - | 0.12 | 0.12 | 0.17 | 0.36 | 0.35 | 0.12 | 0.12 | 0.16 | 0.27 | 0.18 |
| TN:TP ratio | 25 | 25 | 25 | 26 | 42 | 25 | 21 | 24 | 23 | 31 | 6 |
| pH | 8.9 | 8.6 | 8.8 | 8.7 | 8.5 | 8.5 | 8.7 | 8.7 | 8.3 | 8.3 | 8.3 |
| Alkalinity as CaCO3 (mg/L) | 185 | 243 | 214 | 179 | 194 | 178 | 169 | 129 | 166 | 131 | 182 |
| Silica as Si (mg/L) | - | - | - | - | - | 6.30 | 5.44 | 5.76 | 6.80 | - | - |
| Dissolved Organic Carbon (mg/L) | 6.09 | 6.32 | 6.21 | 21.00 | 7.72 | 8.14 | 7.92 | 9.23 | 9.02 | - | - |
| Inorganic Suspended Solids (mg/L) | 1 | 2 | 2 | 1 | 2 | 3 | 2 | 6 | 2 | 2 | 4 |
| Volatile Suspended Solids (mg/L) | 3 | 3 | 3 | 7 | 2 | 4 | 5 | 5 | 5 | 2 | 3 |
| Total Suspended Solids (mg/L) | 4 | 5 | 5 | 7 | 4 | 7 | 8 | 11 | 8 | 5 | 6 |
| Carlson Trophic State Index (Secchi)* | 50 | 44 | 47 | 53 | 47 | 48 | 54 | 53 | 51 | 39 | 50 |
| Carlson Trophic State Index (Chl a)* | 44 | 41 | 43 | 63 | 48 | 72 | 55 | 60 | 51 | 48 | 46 |
| Carlson Trophic State Index (TP)* | 54 | 52 | 53 | 59 | 55 | 62 | 58 | 59 | 59 | 58 | 75 |
| *Index values generally range between 0 and 100, with increasing values indicating more eutrophic conditions. |