| Report Year: 2009 |
| Otter Creek Lake, Tama County |
| Summary Data Table |
| Parameter | 7/27/2009 | 6/22/2009 | 2009 | 2007 | 2006 | 2005 | 2004 | 2003 | 2002 | 2001 | 2000 |
| Lake Depth (m) | 7.4 | 7.3 | 7.4 | - | - | 6.5 | 7.6 | 6.9 | 7.6 | 6.2 | 6.9 |
| Thermocline Depth (m) | 3.0 | 2.0 | N/A | N/A | N/A | N/A | N/A | N/A | N/A | N/A | N/A |
| Secchi Disk Depth (m) | 0.7 | 1.2 | 0.9 | - | - | 0.4 | 0.8 | 1.0 | 1.3 | 1.7 | 0.8 |
| Temperature(oC) | 24.2 | 26.1 | 25.2 | - | - | 26.1 | 24.0 | 24.1 | 25.3 | 24.5 | 25.1 |
| Dissolved Oxygen (mg/L) | 7.1 | 11.3 | 9.2 | - | - | 10.5 | 9.6 | 9.9 | 9.2 | 6.1 | 7.4 |
| Dissolved Oxygen Saturation (%) | 85 | 140 | 112.5 | - | - | 129.8 | 114.6 | 117.8 | 112.3 | 78.5 | 91.2 |
| Specific Conductivity (μS/cm) | 310.0 | 320.0 | 315.0 | - | - | 299.8 | 418.3 | 314.6 | 341.5 | 292.2 | 338.9 |
| Turbidity (NTU) | 7.8 | 7.4 | 7.6 | - | - | 38.1 | 32.6 | 32.3 | 21.9 | 9.2 | 12.7 |
| Chlorophyll a (μg/L) | 53.0 | 35.0 | 44.0 | - | - | 202.7 | 53.8 | 27.9 | 25.1 | 8.7 | 20.5 |
| Total Phosphorus as P (μg/L) | 92 | 56 | 74 | - | - | 82 | 91 | 69 | 135 | 50 | 130 |
| SRP as P (μg/L) | - | - | - | - | - | 1 | 2 | 2 | 59 | - | - |
| Total Nitrogen as N (mg/L) | 1.32 | 1.15 | 1.24 | - | - | 1.61 | 5.37 | 1.33 | 1.24 | 1.64 | 1.10 |
| (Phenate)Ammonia Nitrogen (NH3 + NH4+) as N (μg/L) | - | 20 | 20 | - | - | 267 | 133 | - | - | - | - |
| (Phenate)Ammonia Nitrogen (NH3) as N (un-ionized)(μg/L) | - | 5.6 | 5.6 | - | - | 31.1 | 24.6 | - | - | - | - |
| Nitrate + Nitrite (NO3 + NO2) as N (mg/L) | 0.12 | 0.24 | 0.14 | - | - | 0.15 | 3.51 | 0.17 | 0.12 | 0.54 | 0.15 |
| TN:TP ratio | 14 | 21 | 18 | - | - | 19 | 56 | 20 | 13 | 41 | 11 |
| pH | 8.5 | 8.8 | 8.7 | - | - | 8.8 | 8.7 | 8.5 | 8.4 | 8.0 | 7.4 |
| Alkalinity as CaCO3 (mg/L) | 142 | 152 | 147 | - | - | 136 | 143 | 100 | 143 | 151 | 155 |
| Silica as Si (mg/L) | - | - | - | - | - | 3.67 | 3.42 | 2.65 | 2.71 | - | - |
| Dissolved Organic Carbon (mg/L) | 4.14 | 4.74 | 4.44 | - | - | 6.49 | 4.31 | 9.59 | 9.26 | - | - |
| Inorganic Suspended Solids (mg/L) | 6 | 5 | 5 | - | - | 3 | 3 | 4 | 6 | 1 | 4 |
| Volatile Suspended Solids (mg/L) | 11 | 7 | 9 | - | - | 16 | 10 | 10 | 8 | 4 | 4 |
| Total Suspended Solids (mg/L) | 16 | 12 | 14 | - | - | 19 | 12 | 14 | 12 | 7 | 8 |
| Carlson Trophic State Index (Secchi)* | 66 | 57 | 61 | - | - | 73 | 63 | 60 | 57 | 52 | 63 |
| Carlson Trophic State Index (Chl a)* | 70 | 65 | 68 | - | - | 83 | 70 | 63 | 62 | 52 | 60 |
| Carlson Trophic State Index (TP)* | 69 | 62 | 66 | - | - | 68 | 69 | 65 | 75 | 61 | 74 |
| *Index values generally range between 0 and 100, with increasing values indicating more eutrophic conditions. |