| Report Year: 2011 |
| Arbor Lake, Poweshiek County |
| Summary Data Table |
| Parameter | 6/20/2011 | 8/8/2011 | 9/19/2011 | 2011 | 2010 | 2009 | 2007 | 2006 | 2005 | 2004 | 2003 | 2002 | 2001 | 2000 |
| Lake Depth (m) | 5.1 | 4.9 | 5.1 | 5.0 | 5.3 | 5.4 | 5.4 | 5.2 | - | 5.6 | 5.5 | 5.6 | 5.6 | 5.6 |
| Thermocline Depth (m) | 3.4 | 1.9 | 4.0 | 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) | 1.2 | 0.5 | 0.6 | 0.7 | 0.6 | 1.3 | 0.7 | 0.9 | - | 1.3 | 1.1 | 0.6 | 1.4 | 1.2 |
| Temperature(oC) | 22.5 | 27.8 | 17.6 | 22.6 | 23.8 | 23.5 | 26.6 | 25.9 | - | 22.8 | 25.0 | 25.4 | 22.9 | 24.4 |
| Dissolved Oxygen (mg/L) | 11.8 | 14.8 | 8.5 | 11.7 | 16.3 | 8.5 | 12.8 | 13.0 | - | 13.3 | 10.9 | 9.6 | 11.9 | 10.0 |
| Dissolved Oxygen Saturation (%) | 136 | 189 | 89 | 137.9 | 194.0 | 99.6 | 159.3 | 160.5 | - | 154.3 | 133.5 | 118.3 | 138.3 | 119.5 |
| Specific Conductivity (μS/cm) | 470.0 | 480.0 | 540.0 | 496.7 | 406.7 | 506.7 | 465.3 | 606.3 | - | 450.5 | 478.7 | 401.5 | 455.8 | 349.7 |
| Turbidity (NTU) | 12.1 | 26.5 | 16.2 | 18.3 | 13.5 | 7.9 | 19.7 | 116.9 | - | 13.6 | 14.6 | 44.2 | 11.7 | 13.0 |
| Chlorophyll a (μg/L) | 16.2 | 19.2 | 35.4 | 23.6 | 39.5 | 18.7 | 49.2 | 35.1 | - | 35.3 | 21.1 | 88.5 | 50.1 | 32.1 |
| Total Phosphorus as P (μg/L) | 68.7 | 128.1 | 162.9 | 119.9 | 149.7 | 80.6 | 163 | 120 | - | 109 | 137 | 189 | 156 | - |
| SRP as P (μg/L) | <11 | <11 | 49.4 | 49.4 | <8 | <9 | 44.4 | 40.3 | - | 43.5 | 80.6 | 122.2 | - | - |
| TKN (mg/L) | <0.5 | 1.9 | 0.7 | 1 | 2 | - | - | - | - | - | - | - | - | - |
| Total Dissolved Solids (g/L) | 0.3 | 0.3 | 0.4 | 0.3 | - | - | - | - | - | - | - | - | - | - |
| Total Nitrogen as N (mg/L) | - | - | - | - | - | 1.2 | 2.00 | 1.31 | - | 1.91 | 1.47 | 1.41 | 2.16 | 1.36 |
| (Phenate)Ammonia Nitrogen (NH3 + NH4+) as N (μg/L) | 217.03 | <145 | 292.17 | 177 | <136 | <130 | 96 | 86 | - | 102 | - | - | - | - |
| (Phenate)Ammonia Nitrogen (NH3) as N (un-ionized)(μg/L) | 18 | <PQL | 10 | <PQL | <PQL | <130 | 8 | 23 | - | 19 | - | - | - | - |
| Nitrate + Nitrite (NO3 + NO2) as N (mg/L) | 1.73 | <0.4 | <0.4 | 1 | 1 | - | 0.72 | 0.12 | - | 0.68 | 0.36 | 0.28 | 0.48 | 0.57 |
| TN:TP ratio | - | - | - | - | - | 18 | 14 | 11 | - | 20 | 14 | 8 | 17 | - |
| pH | 8.3 | 8.6 | 8.0 | 8.3 | 8.4 | 8.7 | 8.6 | 8.8 | - | 8.8 | 8.6 | 8.8 | 8.4 | 7.3 |
| Alkalinity as CaCO3 (mg/L) | 142 | 176 | 132 | 150 | 132 | 147 | 130 | 145 | - | 123 | 92 | 96 | 132 | 128 |
| Silica as Si (mg/L) | - | - | - | - | - | - | - | - | - | 6.04 | 4.03 | 6.40 | - | - |
| Dissolved Organic Carbon (mg/L) | <7.6 | <7.6 | <7.6 | <7.6 | <6.4 | <6.2 | 4.76 | 7.01 | - | 3.75 | 8.76 | 8.34 | - | - |
| Inorganic Suspended Solids (mg/L) | 8 | 13 | <5 | 9 | 11 | 7 | 7 | 4 | - | 4 | 6 | 20 | 2 | 5 |
| Volatile Suspended Solids (mg/L) | <8 | 11 | <8 | 8 | 11 | <8 | 8 | 7 | - | 6 | 6 | 11 | 8 | 5 |
| Total Suspended Solids (mg/L) | 14 | 24 | 12 | 17 | 21 | 10 | 16 | 11 | - | 10 | 12 | 29 | 9 | 10 |
| Carlson Trophic State Index (Secchi)* | 58 | 70 | 68 | 64 | 67 | 56 | 65 | 61 | - | 57 | 58 | 69 | 55 | 57 |
| Carlson Trophic State Index (Chl a)* | 58 | 60 | 66 | 62 | 67 | 59 | 69 | 66 | - | 66 | 60 | 75 | 69 | 65 |
| Carlson Trophic State Index (TP)* | 65 | 74 | 78 | 73 | 76 | 67 | 78 | 73 | - | 72 | 75 | 80 | 77 | - |
| *Index values generally range between 0 and 100, with increasing values indicating more eutrophic conditions. |