| Report Year: 2011 |
| Big Hollow Lake, Des Moines County |
| Summary Data Table |
| Parameter | 5/25/2011 | 7/13/2011 | 8/23/2011 | 2011 | 2010 | 2009 | 2007 | 2006 | 2005 | 2004 | 2003 | 2002 | 2001 | 2000 |
| Lake Depth (m) | 9.2 | 7.0 | 8.5 | 8.2 | - | - | - | - | - | - | - | - | - | - |
| Thermocline Depth (m) | 2.3 | 1.8 | 2.4 | 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) | 2.6 | 1.0 | 0.3 | 1.3 | - | - | - | - | - | - | - | - | - | - |
| Temperature(oC) | 21.7 | 27.6 | 26.6 | 25.3 | - | - | - | - | - | - | - | - | - | - |
| Dissolved Oxygen (mg/L) | 11.9 | 15.8 | 16.2 | 14.6 | - | - | - | - | - | - | - | - | - | - |
| Dissolved Oxygen Saturation (%) | 135 | 200 | 202 | 179.0 | - | - | - | - | - | - | - | - | - | - |
| Specific Conductivity (μS/cm) | 490.0 | 330.0 | 370.0 | 396.7 | - | - | - | - | - | - | - | - | - | - |
| Turbidity (NTU) | 2.7 | 10.3 | 21.3 | 11.4 | - | - | - | - | - | - | - | - | - | - |
| Chlorophyll a (μg/L) | 6.9 | 38.4 | 39.5 | 28.3 | - | - | - | - | - | - | - | - | - | - |
| Total Phosphorus as P (μg/L) | 34.4 | 50.7 | 42.4 | 42.5 | - | - | - | - | - | - | - | - | - | - |
| SRP as P (μg/L) | <11 | <11 | <11 | <11 | - | - | - | - | - | - | - | - | - | - |
| TKN (mg/L) | <0.5 | 2.7 | 1.6 | 1 | - | - | - | - | - | - | - | - | - | - |
| Total Dissolved Solids (g/L) | 0.3 | 0.2 | 0.2 | 0.3 | - | - | - | - | - | - | - | - | - | - |
| Total Nitrogen as N (mg/L) | - | - | - | - | - | - | - | - | - | - | - | - | - | - |
| (Phenate)Ammonia Nitrogen (NH3 + NH4+) as N (μg/L) | <145 | <145 | <145 | <145 | - | - | - | - | - | - | - | - | - | - |
| (Phenate)Ammonia Nitrogen (NH3) as N (un-ionized)(μg/L) | <PQL | <PQL | <PQL | <PQL | - | - | - | - | - | - | - | - | - | - |
| Nitrate + Nitrite (NO3 + NO2) as N (mg/L) | 1.17 | 3.52 | 0.99 | 2 | - | - | - | - | - | - | - | - | - | - |
| TN:TP ratio | - | - | - | - | - | - | - | - | - | - | - | - | - | - |
| pH | 8.6 | 9.3 | 9.3 | 9.1 | - | - | - | - | - | - | - | - | - | - |
| Alkalinity as CaCO3 (mg/L) | 132 | 72 | 74 | 93 | - | - | - | - | - | - | - | - | - | - |
| Silica as Si (mg/L) | - | - | - | - | - | - | - | - | - | - | - | - | - | - |
| Dissolved Organic Carbon (mg/L) | <7.6 | <7.6 | <7.6 | <7.6 | - | - | - | - | - | - | - | - | - | - |
| Inorganic Suspended Solids (mg/L) | <5 | 8 | <5 | <5 | - | - | - | - | - | - | - | - | - | - |
| Volatile Suspended Solids (mg/L) | <8 | 9 | 9 | <8 | - | - | - | - | - | - | - | - | - | - |
| Total Suspended Solids (mg/L) | <6 | 17 | 13 | 11 | - | - | - | - | - | - | - | - | - | - |
| Carlson Trophic State Index (Secchi)* | 46 | 60 | 76 | 56 | - | - | - | - | - | - | - | - | - | - |
| Carlson Trophic State Index (Chl a)* | 50 | 66 | 67 | 63 | - | - | - | - | - | - | - | - | - | - |
| Carlson Trophic State Index (TP)* | 55 | 61 | 58 | 58 | - | - | - | - | - | - | - | - | - | - |
| *Index values generally range between 0 and 100, with increasing values indicating more eutrophic conditions. |