| Report Year: 2011 |
| West Okoboji Lake, Dickinson County |
| Summary Data Table |
| Parameter | 6/1/2011 | 7/19/2011 | 8/29/2011 | 2011 | 2010 | 2009 | 2007 | 2006 | 2005 | 2004 | 2003 | 2002 | 2001 | 2000 |
| Lake Depth (m) | 24.9 | 25.4 | 39.1 | 29.8 | 40.4 | 38.5 | 39.1 | 38.4 | 39.6 | 39.4 | 40.9 | 41.0 | 35.3 | 38.0 |
| Thermocline Depth (m) | 16.7 | 5.0 | 11.5 | N/A | N/A | N/A | N/A | N/A | N/A | N/A | N/A | N/A | N/A | N/A |
| Secchi Disk Depth (m) | 8.9 | 5.3 | 3.4 | 5.9 | 5.8 | 7.8 | 3.7 | 4.7 | 5.7 | 5.1 | 8.1 | 5.7 | 6.8 | 5.2 |
| Temperature(oC) | 15.1 | 27.3 | 23.9 | 22.1 | 22.7 | 20.5 | 20.8 | 18.8 | 16.7 | 19.2 | 18.3 | 18.6 | 18.1 | 20.5 |
| Dissolved Oxygen (mg/L) | 9.5 | 9.1 | 9.9 | 9.5 | 8.7 | 10.7 | 10.2 | 9.0 | 10.6 | 9.6 | 10.1 | 10.7 | 8.2 | 8.8 |
| Dissolved Oxygen Saturation (%) | 94 | 115 | 117 | 108.5 | 100.6 | 115.8 | 113.8 | 95.8 | 108.2 | 103.3 | 101.0 | 105.8 | 84.8 | 98.2 |
| Specific Conductivity (μS/cm) | 450.0 | 450.0 | 450.0 | 450.0 | 500.0 | 480.0 | 548.7 | 517.7 | 448.6 | 477.9 | 457.6 | 468.5 | 548.6 | 631.6 |
| Turbidity (NTU) | 0.7 | 1.0 | 1.6 | 1.1 | -0.8 | 0.4 | 7.8 | 3.7 | 3.0 | 28.0 | 0.9 | 1.6 | 0.4 | 0.6 |
| Chlorophyll a (μg/L) | <5 | <5 | <5 | <5 | <5 | <5 | 4.1 | 2.8 | 2.2 | 8.2 | 2.1 | 2.6 | 3.2 | 3.9 |
| Total Phosphorus as P (μg/L) | <15.5 | <15.5 | 16.0 | <15.5 | 18.2 | 14.6 | 22 | 20 | 20 | 18 | 19 | 20 | 47 | - |
| SRP as P (μg/L) | <11 | <11 | <11 | <11 | <8 | <9 | 7.7 | <1 | <1 | <1 | <1 | <1 | - | - |
| TKN (mg/L) | <0.5 | 0.9 | <0.5 | <0.5 | <0.5 | - | - | - | - | - | - | - | - | - |
| Total Dissolved Solids (g/L) | 0.3 | 0.3 | 0.3 | 0.3 | - | - | - | - | - | - | - | - | - | - |
| Total Nitrogen as N (mg/L) | - | - | - | - | - | <0.75 | 0.71 | 0.74 | 0.80 | 0.67 | 0.71 | 0.86 | 0.64 | 0.75 |
| (Phenate)Ammonia Nitrogen (NH3 + NH4+) as N (μg/L) | <145 | <145 | <145 | <145 | <136 | <130 | 40 | 32 | 37 | <26 | - | - | - | - |
| (Phenate)Ammonia Nitrogen (NH3) as N (un-ionized)(μg/L) | <PQL | <PQL | <PQL | <PQL | <PQL | <130 | 5 | 4 | 4 | 1 | - | - | - | - |
| Nitrate + Nitrite (NO3 + NO2) as N (mg/L) | <0.4 | <0.4 | <0.4 | <0.4 | <0.5 | - | 0.16 | 0.12 | 0.19 | 0.14 | 0.12 | 0.22 | 0.12 | 0.19 |
| TN:TP ratio | - | - | - | - | - | 28 | 32 | 38 | 43 | 39 | 37 | 42 | 27 | - |
| pH | 8.5 | 8.5 | 8.3 | 8.4 | 8.6 | 8.6 | 8.5 | 8.4 | 8.5 | 8.6 | 8.5 | 8.5 | 8.3 | 8.3 |
| Alkalinity as CaCO3 (mg/L) | 194 | 189 | 187 | 190 | 194 | 205 | 199 | 141 | 202 | 204 | 154 | 192 | 194 | 199 |
| Silica as Si (mg/L) | - | - | - | - | - | - | - | - | 3.11 | 2.46 | 1.01 | 0.94 | - | - |
| Dissolved Organic Carbon (mg/L) | <7.6 | <7.6 | <7.6 | <7.6 | <6.4 | <6.2 | 5.37 | 6.62 | 5.11 | 6.15 | 9.12 | 9.48 | - | - |
| Inorganic Suspended Solids (mg/L) | <5 | <5 | <5 | <5 | <4 | <4 | 1 | 1 | 2 | 2 | 1 | 2 | 1 | 1 |
| Volatile Suspended Solids (mg/L) | <8 | <8 | <8 | <8 | <9 | <8 | 3 | 3 | 3 | 3 | 1 | 1 | 1 | 1 |
| Total Suspended Solids (mg/L) | <6 | <6 | <6 | <6 | <5 | <5 | 3 | 4 | 5 | 5 | 2 | 4 | 2 | 2 |
| Carlson Trophic State Index (Secchi)* | 28 | 36 | 42 | 35 | 35 | 30 | 41 | 38 | 35 | 37 | 30 | 35 | 32 | 36 |
| Carlson Trophic State Index (Chl a)* | 35 | 40 | 40 | 38 | 39 | 39 | 45 | 41 | 38 | 51 | 38 | 40 | 42 | 44 |
| Carlson Trophic State Index (TP)* | 43 | 43 | 44 | 43 | 46 | 43 | 49 | 47 | 47 | 46 | 47 | 48 | 60 | - |
| *Index values generally range between 0 and 100, with increasing values indicating more eutrophic conditions. |