| Report Year: 2009 |
| Black Hawk Lake, Sac County |
| Summary Data Table |
| Parameter | 6/1/2009 | 7/6/2009 | 2009 | 2007 | 2006 | 2005 | 2004 | 2003 | 2002 | 2001 | 2000 |
| Lake Depth (m) | 2.3 | 2.5 | 2.4 | 3.4 | 2.3 | 2.7 | 2.6 | 4.1 | 2.7 | 2.7 | 2.4 |
| Thermocline Depth (m) | Nil | Nil | N/A | N/A | N/A | N/A | N/A | N/A | N/A | N/A | N/A |
| Secchi Disk Depth (m) | 0.4 | 0.4 | 0.4 | 0.4 | 0.3 | 0.4 | 0.5 | 0.7 | 0.9 | 0.5 | 0.2 |
| Temperature(oC) | 20.7 | 23.7 | 22.2 | 24.7 | 21.8 | 22.4 | 22.5 | 23.7 | 25.1 | 23.1 | 25.7 |
| Dissolved Oxygen (mg/L) | 8.2 | 4.3 | 6.3 | 8.6 | 8.9 | 9.1 | 8.2 | 8.9 | 7.9 | 6.8 | 4.5 |
| Dissolved Oxygen Saturation (%) | 92 | 51 | 71.2 | 103.4 | 99.4 | 103.7 | 94.2 | 105.9 | 95.6 | 78.6 | 55.5 |
| Specific Conductivity (μS/cm) | 470.0 | 470.0 | 470.0 | 448.9 | 488.1 | 484.1 | 466.8 | 518.0 | 621.1 | 524.5 | 480.6 |
| Turbidity (NTU) | 36.7 | 45.1 | 40.9 | 37.2 | 92.6 | 134.0 | 47.3 | 38.7 | 190.4 | 49.0 | 236.9 |
| Chlorophyll a (μg/L) | 29.0 | 21.0 | 25.0 | 59.8 | 44.5 | 115.4 | 47.4 | 22.8 | 30.4 | 9.2 | 79.3 |
| Total Phosphorus as P (μg/L) | 210 | 244 | 227 | 96 | 125 | 126 | 117 | 113 | 193 | 202 | 476 |
| SRP as P (μg/L) | 94 | 109 | 101 | 53 | 6 | 16 | 14 | 8 | 85 | - | - |
| Total Nitrogen as N (mg/L) | 3.57 | 2.46 | 3.02 | 2.77 | 2.15 | 3.21 | 1.74 | 2.64 | 1.92 | 3.15 | 2.39 |
| (Phenate)Ammonia Nitrogen (NH3 + NH4+) as N (μg/L) | 1556 | 612 | 1084 | 290 | 679 | 195 | 139 | - | - | - | - |
| (Phenate)Ammonia Nitrogen (NH3) as N (un-ionized)(μg/L) | 77.7 | 46.4 | 62.0 | 22.7 | 40.0 | 21.3 | 15.9 | - | - | - | - |
| Nitrate + Nitrite (NO3 + NO2) as N (mg/L) | 0.32 | 0.31 | 0.32 | 1.05 | 0.15 | 1.64 | 0.50 | 1.11 | 0.85 | 1.21 | 0.17 |
| TN:TP ratio | 17 | 10 | 14 | 30 | 19 | 30 | 16 | 28 | 14 | 77 | 5 |
| pH | 8.1 | 8.2 | 8.2 | 8.5 | 8.3 | 8.5 | 8.5 | 8.3 | 8.4 | 7.9 | 8.0 |
| Alkalinity as CaCO3 (mg/L) | 223 | 195 | 209 | 171 | 179 | 190 | 170 | 180 | 206 | 147 | 215 |
| Silica as Si (mg/L) | - | - | - | - | - | 4.47 | 3.65 | 4.85 | 8.27 | - | - |
| Dissolved Organic Carbon (mg/L) | 7.02 | 5.18 | 6.10 | 5.55 | 8.10 | 6.59 | 5.48 | 9.52 | 9.67 | - | - |
| Inorganic Suspended Solids (mg/L) | 20 | 25 | 22 | 15 | 23 | 24 | 19 | 15 | 23 | 18 | 40 |
| Volatile Suspended Solids (mg/L) | 11 | 18 | 15 | 14 | 13 | 16 | 6 | 8 | 5 | 11 | 21 |
| Total Suspended Solids (mg/L) | 31 | 43 | 37 | 29 | 37 | 40 | 26 | 24 | 28 | 29 | 60 |
| Carlson Trophic State Index (Secchi)* | 73 | 73 | 73 | 73 | 77 | 74 | 71 | 66 | 61 | 72 | 82 |
| Carlson Trophic State Index (Chl a)* | 64 | 60 | 62 | 71 | 68 | 77 | 68 | 61 | 64 | 52 | 74 |
| Carlson Trophic State Index (TP)* | 81 | 83 | 82 | 70 | 74 | 74 | 73 | 72 | 80 | 81 | 93 |
| *Index values generally range between 0 and 100, with increasing values indicating more eutrophic conditions. |