| Report Year: 2009 |
| Diamond Lake, Poweshiek County |
| Summary Data Table |
| Parameter | 7/20/2009 | 6/16/2009 | 2009 | 2007 | 2006 | 2005 | 2004 | 2003 | 2002 | 2001 | 2000 |
| Lake Depth (m) | 6.3 | 5.7 | 6.0 | 6.2 | 5.9 | 6.4 | 6.4 | 6.3 | 6.0 | 6.3 | 6.4 |
| Thermocline Depth (m) | 0.8 | 2.8 | N/A | N/A | N/A | N/A | N/A | N/A | N/A | N/A | N/A |
| Secchi Disk Depth (m) | 0.7 | 2.2 | 1.4 | 1.0 | 0.7 | 1.2 | 0.8 | 1.0 | 0.9 | 1.8 | 1.2 |
| Temperature(oC) | 25.6 | 22.3 | 24.0 | 26.7 | 26.4 | 25.7 | 23.4 | 24.9 | 26.5 | 23.5 | 25.8 |
| Dissolved Oxygen (mg/L) | 11.5 | 10.0 | 10.8 | 8.9 | 9.1 | 11.3 | 11.6 | 9.8 | 8.6 | 9.5 | 10.4 |
| Dissolved Oxygen Saturation (%) | 141 | 115 | 127.9 | 110.8 | 113.7 | 137.9 | 137.1 | 118.4 | 106.3 | 110.8 | 127.4 |
| Specific Conductivity (μS/cm) | 300.0 | 330.0 | 315.0 | 293.2 | 345.5 | 338.6 | 315.2 | 288.0 | 309.5 | 303.9 | 261.9 |
| Turbidity (NTU) | 9.3 | 6.2 | 7.8 | 15.0 | 10.1 | 116.1 | 503.0 | 14.4 | 18.5 | 6.6 | 6.9 |
| Chlorophyll a (μg/L) | 13.0 | 9.0 | 11.0 | 47.2 | 39.1 | 118.1 | 30.9 | 33.5 | 26.7 | 21.0 | 13.9 |
| Total Phosphorus as P (μg/L) | 66 | 57 | 61 | 87 | 79 | 69 | 103 | 107 | 97 | 84 | 283 |
| SRP as P (μg/L) | - | - | - | 2 | 1 | 4 | 8 | 4 | 8 | - | - |
| Total Nitrogen as N (mg/L) | 1.69 | 2.14 | 1.92 | 1.69 | 1.18 | 1.13 | 1.38 | 1.48 | 1.30 | 1.94 | 1.67 |
| (Phenate)Ammonia Nitrogen (NH3 + NH4+) as N (μg/L) | 17 | 37 | 27 | 51 | 16 | 50 | 116 | - | - | - | - |
| (Phenate)Ammonia Nitrogen (NH3) as N (un-ionized)(μg/L) | 8.2 | 10.0 | 9.1 | 12.1 | 2.5 | 7.4 | 16.0 | - | - | - | - |
| Nitrate + Nitrite (NO3 + NO2) as N (mg/L) | 0.63 | 1.33 | 0.98 | 0.47 | 0.12 | 0.13 | 0.20 | 0.12 | 0.22 | 0.85 | 0.12 |
| TN:TP ratio | 26 | 38 | 32 | 21 | 15 | 16 | 14 | 14 | 17 | 34 | 7 |
| pH | 9.2 | 8.9 | 9.0 | 8.9 | 8.4 | 8.7 | 8.8 | 8.7 | 8.4 | 8.3 | 7.7 |
| Alkalinity as CaCO3 (mg/L) | 127 | 142 | 135 | 110 | 118 | 131 | 109 | 84 | 103 | 130 | 183 |
| Silica as Si (mg/L) | - | - | - | - | - | 2.10 | 5.32 | 3.10 | 3.75 | - | - |
| Dissolved Organic Carbon (mg/L) | 4.42 | 4.93 | 4.68 | 5.53 | 6.75 | 5.07 | 4.65 | 9.58 | 9.69 | - | - |
| Inorganic Suspended Solids (mg/L) | 22 | 4 | 13 | 3 | 6 | 5 | 3 | 3 | 5 | 3 | 1 |
| Volatile Suspended Solids (mg/L) | 3 | 3 | 3 | 6 | 9 | 6 | 8 | 6 | 4 | 3 | 4 |
| Total Suspended Solids (mg/L) | 25 | 7 | 16 | 8 | 15 | 12 | 10 | 10 | 8 | 6 | 6 |
| Carlson Trophic State Index (Secchi)* | 66 | 49 | 55 | 61 | 65 | 58 | 63 | 60 | 62 | 51 | 57 |
| Carlson Trophic State Index (Chl a)* | 56 | 52 | 54 | 68 | 67 | 77 | 64 | 65 | 63 | 60 | 56 |
| Carlson Trophic State Index (TP)* | 64 | 62 | 63 | 69 | 67 | 65 | 71 | 72 | 70 | 68 | 86 |
| *Index values generally range between 0 and 100, with increasing values indicating more eutrophic conditions. |