| Report Year: 2009 |
| Arbor Lake, Poweshiek County |
| Summary Data Table |
| Parameter | 6/15/2009 | 7/20/2009 | 2009 | 2007 | 2006 | 2005 | 2004 | 2003 | 2002 | 2001 | 2000 |
| Lake Depth (m) | 5.5 | 5.3 | 5.4 | 5.4 | 5.2 | - | 5.6 | 5.5 | 5.6 | 5.6 | 5.6 |
| Thermocline Depth (m) | 3.5 | 0.7 | N/A | N/A | N/A | N/A | N/A | N/A | N/A | N/A | N/A |
| Secchi Disk Depth (m) | 2.0 | 0.9 | 1.5 | 0.7 | 0.9 | - | 1.3 | 1.1 | 0.6 | 1.4 | 1.2 |
| Temperature(oC) | 20.2 | 24.2 | 22.2 | 26.6 | 25.9 | - | 22.8 | 25.0 | 25.4 | 22.9 | 24.4 |
| Dissolved Oxygen (mg/L) | 8.0 | 10.2 | 9.1 | 12.8 | 13.0 | - | 13.3 | 10.9 | 9.6 | 11.9 | 10.0 |
| Dissolved Oxygen Saturation (%) | 88 | 122 | 105.1 | 159.3 | 160.5 | - | 154.3 | 133.5 | 118.3 | 138.3 | 119.5 |
| Specific Conductivity (μS/cm) | 550.0 | 490.0 | 520.0 | 465.3 | 606.3 | - | 450.5 | 478.7 | 401.5 | 455.8 | 349.7 |
| Turbidity (NTU) | 3.0 | 11.6 | 7.3 | 19.7 | 116.9 | - | 13.6 | 14.6 | 44.2 | 11.7 | 13.0 |
| Chlorophyll a (μg/L) | 12.0 | 13.0 | 12.5 | 49.2 | 35.1 | - | 35.3 | 21.1 | 88.5 | 50.1 | 32.1 |
| Total Phosphorus as P (μg/L) | 47 | 95 | 71 | 150 | 116 | - | 109 | 138 | 191 | 160 | 319 |
| SRP as P (μg/L) | 1 | - | 1 | 17 | 22 | - | 18 | 29 | 43 | - | - |
| Total Nitrogen as N (mg/L) | 1.44 | 1.16 | 1.30 | 2.00 | 1.31 | - | 1.91 | 1.47 | 1.41 | 2.16 | 1.36 |
| (Phenate)Ammonia Nitrogen (NH3 + NH4+) as N (μg/L) | 102 | 16 | 53 | 93 | 90 | - | 100 | - | - | - | - |
| (Phenate)Ammonia Nitrogen (NH3) as N (un-ionized)(μg/L) | 7.6 | 0.9 | 4.2 | 7.9 | 24.2 | - | 18.6 | - | - | - | - |
| Nitrate + Nitrite (NO3 + NO2) as N (mg/L) | 0.57 | 0.12 | 0.31 | 0.72 | 0.12 | - | 0.66 | 0.37 | 0.28 | 0.49 | 0.57 |
| TN:TP ratio | 30 | 12 | 21 | 18 | 12 | - | 20 | 14 | 8 | 16 | 5 |
| pH | 8.3 | 8.9 | 8.6 | 8.6 | 8.8 | - | 8.8 | 8.6 | 8.8 | 8.4 | 7.3 |
| Alkalinity as CaCO3 (mg/L) | 156 | 147 | 152 | 130 | 145 | - | 123 | 92 | 96 | 132 | 128 |
| Silica as Si (mg/L) | - | - | - | - | - | - | 6.04 | 4.03 | 6.40 | - | - |
| Dissolved Organic Carbon (mg/L) | 4.30 | 4.75 | 4.53 | 4.76 | 7.01 | - | 3.75 | 8.76 | 8.34 | - | - |
| Inorganic Suspended Solids (mg/L) | 5 | 11 | 8 | 7 | 4 | - | 4 | 6 | 20 | 2 | 5 |
| Volatile Suspended Solids (mg/L) | 2 | - | 2 | 9 | 7 | - | 6 | 6 | 11 | 8 | 5 |
| Total Suspended Solids (mg/L) | 7 | 11 | 9 | 16 | 11 | - | 10 | 12 | 29 | 9 | 10 |
| Carlson Trophic State Index (Secchi)* | 50 | 62 | 55 | 65 | 61 | - | 57 | 58 | 69 | 55 | 57 |
| Carlson Trophic State Index (Chl a)* | 55 | 56 | 55 | 69 | 66 | - | 66 | 60 | 75 | 69 | 65 |
| Carlson Trophic State Index (TP)* | 60 | 70 | 66 | 76 | 73 | - | 72 | 75 | 80 | 77 | 87 |
| *Index values generally range between 0 and 100, with increasing values indicating more eutrophic conditions. |