| Report Year: 2009 |
| Hawthorn Lake (Barnes City Lake), Mahaska County |
| Summary Data Table |
| Parameter | 7/20/2009 | 6/16/2009 | 2009 | 2007 | 2006 | 2005 | 2004 | 2003 | 2002 | 2001 | 2000 |
| Lake Depth (m) | 7.5 | 7.7 | 7.6 | - | - | 8.1 | 8.8 | 8.6 | 8.4 | 8.6 | 8.2 |
| Thermocline Depth (m) | 6.2 | 4.5 | N/A | N/A | N/A | N/A | N/A | N/A | N/A | N/A | N/A |
| Secchi Disk Depth (m) | 0.6 | 0.7 | 0.6 | - | - | 0.9 | 0.8 | 1.3 | 0.9 | 1.1 | 0.5 |
| Temperature(oC) | 22.9 | 21.2 | 22.0 | - | - | 27.0 | 23.2 | 24.9 | 26.6 | 22.8 | 25.2 |
| Dissolved Oxygen (mg/L) | 6.0 | 9.0 | 7.5 | - | - | 7.6 | 8.8 | 8.8 | 9.2 | 7.7 | 7.5 |
| Dissolved Oxygen Saturation (%) | 69 | 101 | 85.2 | - | - | 95.4 | 102.6 | 107.7 | 114.9 | 90.0 | 91.4 |
| Specific Conductivity (μS/cm) | 280.0 | 280.0 | 280.0 | - | - | 327.9 | 310.9 | 287.4 | 440.1 | 241.8 | 265.8 |
| Turbidity (NTU) | 13.4 | 9.7 | 11.5 | - | - | 74.6 | 43.6 | 12.2 | 22.4 | 17.5 | 128.2 |
| Chlorophyll a (μg/L) | 10.0 | 9.0 | 9.5 | - | - | 30.0 | 28.7 | 15.3 | 45.7 | 35.5 | 12.9 |
| Total Phosphorus as P (μg/L) | 71 | 65 | 68 | - | - | 56 | 43 | 45 | 48 | 50 | 150 |
| SRP as P (μg/L) | - | - | - | - | - | 1 | 1 | 1 | 1 | - | - |
| Total Nitrogen as N (mg/L) | 1.31 | 1.63 | 1.47 | - | - | 0.99 | 1.26 | 1.24 | 1.16 | 1.83 | 1.29 |
| (Phenate)Ammonia Nitrogen (NH3 + NH4+) as N (μg/L) | 48 | 141 | 95 | - | - | 27 | 75 | - | - | - | - |
| (Phenate)Ammonia Nitrogen (NH3) as N (un-ionized)(μg/L) | 6.4 | 7.3 | 6.8 | - | - | 0.4 | 7.1 | - | - | - | - |
| Nitrate + Nitrite (NO3 + NO2) as N (mg/L) | 0.21 | 0.79 | 0.50 | - | - | 0.12 | 0.47 | 0.31 | 0.29 | 0.87 | 0.13 |
| TN:TP ratio | 19 | 25 | 22 | - | - | 18 | 29 | 33 | 28 | 42 | 9 |
| pH | 8.5 | 8.1 | 8.3 | - | - | 8.2 | 8.4 | 8.4 | 8.0 | 8.2 | 7.5 |
| Alkalinity as CaCO3 (mg/L) | 117 | 116 | 117 | - | - | 135 | 114 | 82 | 96 | 99 | 172 |
| Silica as Si (mg/L) | - | - | - | - | - | 1.94 | 2.49 | 1.76 | 2.23 | - | - |
| Dissolved Organic Carbon (mg/L) | 4.69 | 4.61 | 4.65 | - | - | 6.17 | 4.01 | 9.70 | 8.24 | - | - |
| Inorganic Suspended Solids (mg/L) | 14 | 7 | 11 | - | - | 5 | 7 | 5 | 5 | 6 | 8 |
| Volatile Suspended Solids (mg/L) | 1 | 5 | 3 | - | - | 5 | 6 | 4 | 9 | 5 | 6 |
| Total Suspended Solids (mg/L) | 16 | 12 | 14 | - | - | 10 | 13 | 10 | 14 | 10 | 14 |
| Carlson Trophic State Index (Secchi)* | 67 | 66 | 67 | - | - | 62 | 63 | 56 | 62 | 59 | 69 |
| Carlson Trophic State Index (Chl a)* | 53 | 52 | 53 | - | - | 64 | 64 | 57 | 68 | 66 | 56 |
| Carlson Trophic State Index (TP)* | 66 | 64 | 65 | - | - | 62 | 58 | 59 | 60 | 61 | 76 |
| *Index values generally range between 0 and 100, with increasing values indicating more eutrophic conditions. |