| Report Year: 2011 |
| Hawthorn Lake (Barnes City Lake), Mahaska 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) | 7.3 | 7.3 | 7.4 | 7.3 | - | 7.6 | - | - | 8.1 | 8.8 | 8.6 | 8.4 | 8.6 | 8.2 |
| Thermocline Depth (m) | 2.5 | 3.1 | 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) | 0.6 | 0.9 | 1.0 | 0.8 | - | 0.6 | - | - | 0.9 | 0.8 | 1.3 | 0.9 | 1.1 | 0.5 |
| Temperature(oC) | 22.7 | 29.1 | 18.4 | 23.4 | - | 23.3 | - | - | 27.0 | 23.2 | 24.9 | 26.6 | 22.8 | 25.2 |
| Dissolved Oxygen (mg/L) | 10.0 | 9.5 | 5.7 | 8.4 | - | 6.8 | - | - | 7.6 | 8.8 | 8.8 | 9.2 | 7.7 | 7.5 |
| Dissolved Oxygen Saturation (%) | 116 | 124 | 61 | 100.3 | - | 79.6 | - | - | 95.4 | 102.6 | 107.7 | 114.9 | 90.0 | 91.4 |
| Specific Conductivity (μS/cm) | 380.0 | 320.0 | 340.0 | 346.7 | - | 290.0 | - | - | 327.9 | 310.9 | 287.4 | 440.1 | 241.8 | 265.8 |
| Turbidity (NTU) | 34.9 | 7.2 | 6.2 | 16.1 | - | 11.3 | - | - | 74.6 | 43.6 | 12.2 | 22.4 | 17.5 | 128.2 |
| Chlorophyll a (μg/L) | 102.8 | 46.5 | 25.0 | 58.1 | - | 17.0 | - | - | 30.0 | 28.7 | 15.3 | 45.7 | 35.5 | 12.9 |
| Total Phosphorus as P (μg/L) | 63.5 | 52.4 | 70.0 | 62.0 | - | 74.2 | - | - | 56 | 44 | 45 | 49 | 51 | - |
| SRP as P (μg/L) | <11 | <11 | <11 | <11 | - | <9 | - | - | <1 | 1.3 | 2.1 | <1 | - | - |
| TKN (mg/L) | 1.4 | 1.4 | 1.3 | 1 | - | - | - | - | - | - | - | - | - | - |
| Total Dissolved Solids (g/L) | 0.3 | 0.2 | 0.2 | 0.2 | - | - | - | - | - | - | - | - | - | - |
| Total Nitrogen as N (mg/L) | - | - | - | - | - | 1.3 | - | - | 0.99 | 1.26 | 1.24 | 1.16 | 1.83 | 1.29 |
| (Phenate)Ammonia Nitrogen (NH3 + NH4+) as N (μg/L) | <145 | <145 | 193.27 | <145 | - | <130 | - | - | 27 | 74 | - | - | - | - |
| (Phenate)Ammonia Nitrogen (NH3) as N (un-ionized)(μg/L) | <PQL | <PQL | 4 | <PQL | - | <130 | - | - | 0 | 7 | - | - | - | - |
| Nitrate + Nitrite (NO3 + NO2) as N (mg/L) | 0.81 | <0.4 | <0.4 | <0.4 | - | - | - | - | 0.13 | 0.48 | 0.31 | 0.29 | 0.83 | 0.12 |
| TN:TP ratio | - | - | - | - | - | 19 | - | - | 18 | 29 | 32 | 27 | 39 | - |
| pH | 8.4 | 8.4 | 7.8 | 8.2 | - | 8.3 | - | - | 8.2 | 8.4 | 8.4 | 8.0 | 8.2 | 7.5 |
| Alkalinity as CaCO3 (mg/L) | 119 | 130 | 121 | 123 | - | 112 | - | - | 135 | 114 | 82 | 96 | 99 | 172 |
| Silica as Si (mg/L) | - | - | - | - | - | - | - | - | 1.94 | 2.49 | 1.76 | 2.23 | - | - |
| Dissolved Organic Carbon (mg/L) | <7.6 | <7.6 | <7.6 | <7.6 | - | <6.2 | - | - | 6.17 | 4.01 | 9.70 | 8.24 | - | - |
| Inorganic Suspended Solids (mg/L) | 8 | <5 | <5 | 5 | - | 11 | - | - | 4 | 7 | 5 | 5 | 6 | 8 |
| Volatile Suspended Solids (mg/L) | 13 | <8 | <8 | <8 | - | <8 | - | - | 5 | 6 | 4 | 9 | 5 | 6 |
| Total Suspended Solids (mg/L) | 21 | 10 | 7 | 13 | - | 15 | - | - | 10 | 13 | 10 | 14 | 10 | 14 |
| Carlson Trophic State Index (Secchi)* | 68 | 62 | 61 | 63 | - | 67 | - | - | 62 | 63 | 56 | 62 | 59 | 69 |
| Carlson Trophic State Index (Chl a)* | 76 | 68 | 62 | 70 | - | 58 | - | - | 64 | 64 | 57 | 68 | 66 | 56 |
| Carlson Trophic State Index (TP)* | 64 | 61 | 65 | 64 | - | 66 | - | - | 62 | 59 | 59 | 60 | 61 | - |
| *Index values generally range between 0 and 100, with increasing values indicating more eutrophic conditions. |