| Report Year: 2011 |
| Otter Creek Lake, Tama County |
| Summary Data Table |
| Parameter | 6/22/2011 | 8/10/2011 | 9/21/2011 | 2011 | 2010 | 2009 | 2007 | 2006 | 2005 | 2004 | 2003 | 2002 | 2001 | 2000 |
| Lake Depth (m) | 7.2 | 6.7 | 7.3 | 7.1 | 7.2 | 7.2 | - | - | 6.5 | 7.6 | 6.9 | 7.6 | 6.2 | 6.9 |
| Thermocline Depth (m) | Nil | 3.3 | Nil | 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) | 0.5 | 0.5 | 0.5 | 0.5 | 0.7 | 0.8 | - | - | 0.4 | 0.8 | 1.0 | 1.3 | 1.7 | 0.8 |
| Temperature(oC) | 20.8 | 26.4 | 17.6 | 21.6 | 22.6 | 25.9 | - | - | 26.1 | 24.0 | 24.1 | 25.3 | 24.5 | 25.1 |
| Dissolved Oxygen (mg/L) | 6.0 | 6.0 | 5.6 | 5.9 | 8.3 | 9.3 | - | - | 10.5 | 9.6 | 9.9 | 9.2 | 6.1 | 7.4 |
| Dissolved Oxygen Saturation (%) | 67 | 75 | 59 | 66.9 | 99.2 | 114.8 | - | - | 129.8 | 114.6 | 117.8 | 112.3 | 78.5 | 91.2 |
| Specific Conductivity (μS/cm) | 360.0 | 300.0 | 300.0 | 320.0 | 325.0 | 300.0 | - | - | 299.8 | 418.3 | 314.6 | 341.5 | 292.2 | 338.9 |
| Turbidity (NTU) | 20.3 | 43.0 | 17.0 | 26.7 | 9.9 | 11.3 | - | - | 38.1 | 32.6 | 32.3 | 21.9 | 9.2 | 12.7 |
| Chlorophyll a (μg/L) | 103.0 | 54.3 | 64.3 | 73.9 | 32.5 | 47.0 | - | - | 202.7 | 53.8 | 27.9 | 25.1 | 8.7 | 20.5 |
| Total Phosphorus as P (μg/L) | 55.3 | 98.0 | 116.5 | 89.9 | 59.8 | 74.9 | - | - | 81 | 89 | 69 | 135 | 53 | - |
| SRP as P (μg/L) | <11 | <11 | <11 | <11 | <8 | <9 | - | - | <1 | 2.8 | 2.6 | 172.4 | - | - |
| TKN (mg/L) | 1.7 | 1.2 | 2.9 | 2 | 2 | - | - | - | - | - | - | - | - | - |
| Total Dissolved Solids (g/L) | 0.2 | 0.2 | 0.2 | 0.2 | - | - | - | - | - | - | - | - | - | - |
| Total Nitrogen as N (mg/L) | - | - | - | - | - | 1.2 | - | - | 1.61 | 5.37 | 1.33 | 1.24 | 1.64 | 1.10 |
| (Phenate)Ammonia Nitrogen (NH3 + NH4+) as N (μg/L) | <145 | <145 | 684.86 | 238 | 187 | <130 | - | - | 267 | 145 | - | - | - | - |
| (Phenate)Ammonia Nitrogen (NH3) as N (un-ionized)(μg/L) | <PQL | <PQL | 27 | <PQL | <PQL | <130 | - | - | 31 | 28 | - | - | - | - |
| Nitrate + Nitrite (NO3 + NO2) as N (mg/L) | <0.4 | <0.4 | <0.4 | <0.4 | <0.5 | - | - | - | 0.15 | 3.50 | 0.19 | 0.12 | 0.56 | 0.15 |
| TN:TP ratio | - | - | - | - | - | 17 | - | - | 19 | 58 | 20 | 13 | 40 | - |
| pH | 8.2 | 8.5 | 8.1 | 8.3 | 8.5 | 8.8 | - | - | 8.8 | 8.7 | 8.5 | 8.4 | 8.0 | 7.4 |
| Alkalinity as CaCO3 (mg/L) | 147 | 138 | 120 | 135 | 149 | 140 | - | - | 136 | 143 | 100 | 143 | 151 | 155 |
| Silica as Si (mg/L) | - | - | - | - | - | - | - | - | 3.67 | 3.42 | 2.65 | 2.71 | - | - |
| Dissolved Organic Carbon (mg/L) | <7.6 | <7.6 | <7.6 | <7.6 | <6.4 | <6.2 | - | - | 6.49 | 4.31 | 9.59 | 9.26 | - | - |
| Inorganic Suspended Solids (mg/L) | <5 | 7 | <5 | <5 | <4 | <4 | - | - | 3 | 3 | 4 | 6 | 1 | 4 |
| Volatile Suspended Solids (mg/L) | 13 | 15 | 9 | 12 | 9 | 11 | - | - | 16 | 10 | 10 | 8 | 4 | 4 |
| Total Suspended Solids (mg/L) | 14 | 22 | 9 | 15 | 10 | 14 | - | - | 19 | 12 | 14 | 12 | 7 | 8 |
| Carlson Trophic State Index (Secchi)* | 71 | 72 | 70 | 71 | 64 | 63 | - | - | 73 | 63 | 60 | 57 | 52 | 63 |
| Carlson Trophic State Index (Chl a)* | 76 | 70 | 71 | 73 | 65 | 68 | - | - | 83 | 70 | 63 | 62 | 52 | 60 |
| Carlson Trophic State Index (TP)* | 62 | 70 | 73 | 69 | 63 | 66 | - | - | 68 | 69 | 65 | 75 | 61 | - |
| *Index values generally range between 0 and 100, with increasing values indicating more eutrophic conditions. |