| Report Year: 2011 |
| Arrowhead Lake (Sac), Sac County |
| Summary Data Table |
| Parameter | 5/17/2011 | 6/28/2011 | 8/17/2011 | 2011 | 2010 | 2009 | 2007 | 2006 | 2005 | 2004 | 2003 | 2002 | 2001 | 2000 |
| Lake Depth (m) | 5.9 | 5.9 | 5.6 | 5.8 | 5.9 | 5.7 | 5.9 | 4.4 | 6.0 | 6.1 | 6.2 | 5.7 | 6.3 | 5.7 |
| Thermocline Depth (m) | Nil | Nil | 5.0 | 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) | 5.0 | 1.7 | 2.7 | 3.1 | 3.3 | 3.6 | 3.3 | 2.1 | 2.1 | 2.3 | 4.0 | 3.6 | 2.9 | 2.4 |
| Temperature(oC) | 16.0 | 21.7 | 26.0 | 21.2 | 23.5 | 23.0 | 24.5 | 25.0 | 23.1 | 22.7 | 22.9 | 22.7 | 22.7 | 25.2 |
| Dissolved Oxygen (mg/L) | 9.3 | 7.0 | 6.8 | 7.7 | 8.1 | 9.4 | 7.6 | 9.1 | 9.0 | 8.7 | 9.5 | 9.8 | 10.5 | 8.1 |
| Dissolved Oxygen Saturation (%) | 94 | 80 | 84 | 86.2 | 93.9 | 110.0 | 91.2 | 109.9 | 104.0 | 99.9 | 109.5 | 112.0 | 112.2 | 98.1 |
| Specific Conductivity (μS/cm) | 490.0 | 480.0 | 480.0 | 483.3 | 510.0 | 486.7 | 488.2 | 495.1 | 490.7 | 488.0 | 451.8 | 464.2 | 545.4 | 629.6 |
| Turbidity (NTU) | 0.9 | 4.6 | 3.0 | 2.8 | 1.5 | 2.0 | 4.1 | 5.4 | 5.9 | 5.4 | 2.4 | 3.0 | 5.0 | 2.6 |
| Chlorophyll a (μg/L) | <5 | 10.7 | 6.7 | 6.8 | <5 | <5 | 5.4 | 6.0 | 14.7 | 8.7 | 5.8 | 6.3 | 8.8 | 7.9 |
| Total Phosphorus as P (μg/L) | 19.5 | 18.9 | 22.0 | 20.2 | 31.5 | 21.8 | 90 | 23 | 25 | 28 | 23 | 27 | 15 | - |
| SRP as P (μg/L) | <11 | <11 | <11 | <11 | <8 | <9 | <1 | <1 | <1 | <1 | 1.3 | <1 | - | - |
| TKN (mg/L) | 0.6 | <0.5 | 2.5 | 1 | <0.5 | - | - | - | - | - | - | - | - | - |
| Total Dissolved Solids (g/L) | 0.3 | 0.3 | 0.3 | 0.3 | - | - | - | - | - | - | - | - | - | - |
| Total Nitrogen as N (mg/L) | - | - | - | - | - | <0.75 | 2.50 | 0.82 | 0.77 | 0.68 | 0.68 | 0.78 | 0.88 | 0.76 |
| (Phenate)Ammonia Nitrogen (NH3 + NH4+) as N (μg/L) | <145 | <145 | <145 | <145 | <136 | <130 | <26 | <26 | <26 | <26 | - | - | - | - |
| (Phenate)Ammonia Nitrogen (NH3) as N (un-ionized)(μg/L) | <PQL | <PQL | <PQL | <PQL | <PQL | <130 | 2 | 3 | 2 | 1 | - | - | - | - |
| Nitrate + Nitrite (NO3 + NO2) as N (mg/L) | <0.4 | <0.4 | <0.4 | <0.4 | <0.5 | - | 1.72 | 0.12 | 0.12 | 0.12 | 0.12 | 0.16 | 0.17 | 0.14 |
| TN:TP ratio | - | - | - | - | - | 34 | 17 | 36 | 32 | 28 | 30 | 31 | 67 | - |
| pH | 8.3 | 8.1 | 8.2 | 8.2 | 8.4 | 8.4 | 8.3 | 8.4 | 8.4 | 8.4 | 8.3 | 8.4 | 8.2 | 8.0 |
| Alkalinity as CaCO3 (mg/L) | 227 | 213 | 209 | 217 | 201 | 233 | 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) | <7.6 | <7.6 | <7.6 | <7.6 | <6.4 | <6.2 | 6.06 | 6.61 | 7.01 | 5.13 | 9.25 | - | - | - |
| Inorganic Suspended Solids (mg/L) | <5 | <5 | <5 | <5 | <4 | <4 | 2 | 2 | 1 | 3 | 1 | 2 | 2 | 2 |
| Volatile Suspended Solids (mg/L) | <8 | <8 | <8 | <8 | <9 | <8 | 3 | 5 | 5 | 4 | 4 | 2 | 3 | 3 |
| Total Suspended Solids (mg/L) | <6 | <6 | <6 | <6 | <5 | <5 | 4 | 7 | 6 | 7 | 5 | 4 | 4 | 5 |
| Carlson Trophic State Index (Secchi)* | 37 | 52 | 46 | 44 | 43 | 42 | 43 | 50 | 49 | 48 | 40 | 41 | 45 | 47 |
| Carlson Trophic State Index (Chl a)* | 41 | 54 | 49 | 49 | 46 | 42 | 47 | 48 | 57 | 52 | 48 | 49 | 52 | 51 |
| Carlson Trophic State Index (TP)* | 47 | 47 | 49 | 47 | 54 | 49 | 69 | 49 | 50 | 52 | 49 | 52 | 43 | - |
| *Index values generally range between 0 and 100, with increasing values indicating more eutrophic conditions. |