| Report Year: 2009 |
| Arrowhead Lake (Sac), Sac County |
| Summary Data Table |
| Parameter | 6/1/2009 | 7/6/2009 | 2009 | 2007 | 2006 | 2005 | 2004 | 2003 | 2002 | 2001 | 2000 |
| Lake Depth (m) | 5.5 | 5.7 | 5.6 | 5.9 | 4.4 | 6.0 | 6.1 | 6.2 | 5.7 | 6.3 | 5.7 |
| Thermocline Depth (m) | Nil | 4.6 | N/A | N/A | N/A | N/A | N/A | N/A | N/A | N/A | N/A |
| Secchi Disk Depth (m) | 4.7 | 2.4 | 3.5 | 3.3 | 2.1 | 2.1 | 2.3 | 4.0 | 3.6 | 2.9 | 2.4 |
| Temperature(oC) | 20.5 | 24.0 | 22.2 | 24.5 | 25.0 | 23.1 | 22.7 | 22.9 | 22.7 | 22.7 | 25.2 |
| Dissolved Oxygen (mg/L) | 9.0 | 11.9 | 10.5 | 7.6 | 9.1 | 9.0 | 8.7 | 9.5 | 9.8 | 10.5 | 8.1 |
| Dissolved Oxygen Saturation (%) | 100 | 142 | 120.6 | 91.2 | 109.9 | 104.0 | 99.9 | 109.5 | 112.0 | 112.2 | 98.1 |
| Specific Conductivity (μS/cm) | 520.0 | 480.0 | 500.0 | 488.2 | 495.1 | 490.7 | 488.0 | 451.8 | 464.2 | 545.4 | 629.6 |
| Turbidity (NTU) | 2.4 | 2.2 | 2.3 | 4.1 | 5.4 | 5.9 | 5.4 | 2.4 | 3.0 | 5.0 | 2.6 |
| Chlorophyll a (μg/L) | 2.0 | 5.0 | 3.5 | 5.4 | 6.0 | 14.7 | 8.7 | 5.8 | 6.3 | 8.8 | 7.9 |
| Total Phosphorus as P (μg/L) | 16 | 25 | 21 | 88 | 22 | 25 | 30 | 23 | 26 | 14 | 148 |
| SRP as P (μg/L) | - | - | - | 1 | 1 | 1 | 1 | 1 | 1 | - | - |
| Total Nitrogen as N (mg/L) | 0.74 | 0.80 | 0.77 | 3.80 | 0.82 | 0.77 | 0.68 | 0.68 | 0.78 | 0.88 | 0.76 |
| (Phenate)Ammonia Nitrogen (NH3 + NH4+) as N (μg/L) | 103 | 21 | 62 | 23 | 41 | 35 | 19 | - | - | - | - |
| (Phenate)Ammonia Nitrogen (NH3) as N (un-ionized)(μg/L) | 9.6 | 3.0 | 6.3 | 2.3 | 6.9 | 4.4 | 2.0 | - | - | - | - |
| Nitrate + Nitrite (NO3 + NO2) as N (mg/L) | 0.19 | 0.12 | 0.12 | 1.70 | 0.12 | 0.12 | 0.12 | 0.12 | 0.15 | 0.17 | 0.14 |
| TN:TP ratio | 45 | 32 | 39 | 31 | 37 | 31 | 26 | 30 | 32 | 68 | 13 |
| pH | 8.4 | 8.5 | 8.4 | 8.3 | 8.4 | 8.4 | 8.4 | 8.3 | 8.4 | 8.2 | 8.0 |
| Alkalinity as CaCO3 (mg/L) | 288 | 210 | 249 | 202 | 190 | 187 | 190 | 139 | 166 | 149 | 184 |
| Silica as Si (mg/L) | - | - | - | - | - | 2.33 | 1.73 | 1.11 | 1.53 | - | - |
| Dissolved Organic Carbon (mg/L) | 4.58 | 4.81 | 4.70 | 6.06 | 6.61 | 7.01 | 5.13 | 9.25 | - | - | - |
| Inorganic Suspended Solids (mg/L) | - | 1 | 1 | 2 | 2 | 2 | 3 | 1 | 2 | 2 | 2 |
| Volatile Suspended Solids (mg/L) | 3 | 5 | 4 | 3 | 5 | 4 | 4 | 4 | 2 | 3 | 3 |
| Total Suspended Solids (mg/L) | 3 | 5 | 4 | 4 | 7 | 6 | 7 | 5 | 4 | 6 | 5 |
| Carlson Trophic State Index (Secchi)* | 38 | 48 | 42 | 43 | 50 | 49 | 48 | 40 | 41 | 45 | 47 |
| Carlson Trophic State Index (Chl a)* | 37 | 46 | 43 | 47 | 48 | 57 | 52 | 48 | 49 | 52 | 51 |
| Carlson Trophic State Index (TP)* | 44 | 50 | 48 | 69 | 49 | 51 | 53 | 49 | 51 | 42 | 76 |
| *Index values generally range between 0 and 100, with increasing values indicating more eutrophic conditions. |