| Report Year: 2009 |
| East Okoboji Lake, Dickinson County |
| Summary Data Table |
| Parameter | 7/8/2009 | 6/3/2009 | 2009 | 2007 | 2006 | 2005 | 2004 | 2003 | 2002 | 2001 | 2000 |
| Lake Depth (m) | 6.5 | 6.5 | 6.5 | 6.4 | 6.1 | 6.8 | 5.7 | 5.9 | 6.3 | 6.0 | 6.0 |
| Thermocline Depth (m) | Nil | Nil | N/A | N/A | N/A | N/A | N/A | N/A | N/A | N/A | N/A |
| Secchi Disk Depth (m) | 3.2 | 2.5 | 2.8 | 1.2 | 2.3 | 2.2 | 1.5 | 2.9 | 0.9 | 3.6 | 1.1 |
| Temperature(oC) | 23.9 | 18.5 | 21.2 | 22.5 | 21.5 | 20.3 | 21.4 | 21.3 | 20.4 | 21.8 | 24.4 |
| Dissolved Oxygen (mg/L) | 6.5 | 10.1 | 8.3 | 7.6 | 8.9 | 9.2 | 9.6 | 8.6 | 8.8 | 8.8 | 9.6 |
| Dissolved Oxygen Saturation (%) | 77 | 108 | 92.4 | 88.4 | 100.3 | 101.1 | 108.6 | 95.1 | 95.7 | 102.9 | 115.0 |
| Specific Conductivity (μS/cm) | 510.0 | 490.0 | 500.0 | 496.4 | 514.6 | 530.5 | 559.6 | 518.2 | 528.9 | 506.6 | 624.5 |
| Turbidity (NTU) | 16.1 | 2.8 | 9.4 | 18.0 | 5.4 | 24.1 | 14.0 | 91.7 | 17.0 | 5.0 | 9.5 |
| Chlorophyll a (μg/L) | 2.0 | 2.0 | 2.0 | 19.2 | 14.6 | 24.6 | 13.8 | 6.4 | 19.0 | 9.9 | 22.1 |
| Total Phosphorus as P (μg/L) | 54 | 29 | 42 | 113 | 90 | 70 | 90 | 55 | 66 | 57 | 190 |
| SRP as P (μg/L) | 34 | 11 | 23 | 54 | 33 | 34 | 26 | 17 | 2 | - | - |
| Total Nitrogen as N (mg/L) | 0.97 | 0.79 | 0.88 | 1.30 | 1.39 | 1.23 | 1.14 | 1.10 | 1.03 | 1.14 | 1.14 |
| (Phenate)Ammonia Nitrogen (NH3 + NH4+) as N (μg/L) | 103 | 69 | 86 | 34 | 112 | 83 | 82 | - | - | - | - |
| (Phenate)Ammonia Nitrogen (NH3) as N (un-ionized)(μg/L) | 12.0 | 6.9 | 9.5 | 3.0 | 9.5 | 5.4 | 7.7 | - | - | - | - |
| Nitrate + Nitrite (NO3 + NO2) as N (mg/L) | 0.12 | 0.16 | 0.14 | 0.26 | 0.32 | 0.46 | 0.17 | 0.24 | 0.18 | 0.53 | 0.21 |
| TN:TP ratio | 18 | 27 | 22 | 16 | 21 | 27 | 13 | 24 | 16 | 21 | 6 |
| pH | 8.4 | 8.5 | 8.4 | 8.5 | 8.4 | 8.4 | 8.5 | 8.4 | 8.4 | 8.2 | 8.4 |
| Alkalinity as CaCO3 (mg/L) | 201 | 216 | 209 | 200 | 208 | 202 | 215 | 157 | 194 | 141 | 205 |
| Silica as Si (mg/L) | - | - | - | - | - | 6.46 | 6.52 | 6.23 | 3.33 | - | - |
| Dissolved Organic Carbon (mg/L) | 6.03 | 6.28 | 6.16 | 6.68 | 6.82 | 5.11 | 9.50 | 9.75 | 9.36 | - | - |
| Inorganic Suspended Solids (mg/L) | 1 | 1 | 1 | 3 | 2 | 5 | 3 | 3 | 9 | 2 | 5 |
| Volatile Suspended Solids (mg/L) | 3 | 1 | 2 | 8 | 3 | 4 | 5 | 2 | 7 | 2 | 4 |
| Total Suspended Solids (mg/L) | 4 | 2 | 3 | 11 | 6 | 9 | 9 | 5 | 16 | 4 | 9 |
| Carlson Trophic State Index (Secchi)* | 43 | 47 | 45 | 58 | 48 | 48 | 54 | 44 | 61 | 41 | 59 |
| Carlson Trophic State Index (Chl a)* | 37 | 37 | 37 | 60 | 57 | 62 | 56 | 49 | 59 | 53 | 61 |
| Carlson Trophic State Index (TP)* | 62 | 53 | 58 | 72 | 69 | 65 | 69 | 62 | 64 | 63 | 80 |
| *Index values generally range between 0 and 100, with increasing values indicating more eutrophic conditions. |