| Report Year: 2009 |
| Arrowhead Pond (Pottawattamie), Pottawattamie County |
| Summary Data Table |
| Parameter | 7/14/2009 | 6/10/2009 | 2009 | 2007 | 2006 | 2005 | 2004 | 2003 | 2002 | 2001 | 2000 |
| Lake Depth (m) | 4.1 | 3.9 | 4.0 | - | - | 4.0 | 4.1 | 4.0 | 4.0 | 4.3 | 4.0 |
| Thermocline Depth (m) | 1.5 | 3.7 | N/A | N/A | N/A | N/A | N/A | N/A | N/A | N/A | N/A |
| Secchi Disk Depth (m) | 0.8 | 0.5 | 0.7 | - | - | 0.5 | 0.4 | 0.7 | 0.9 | 1.2 | 0.9 |
| Temperature(oC) | 25.2 | 19.7 | 22.5 | - | - | 24.3 | 21.4 | 24.3 | 26.3 | 23.1 | 25.1 |
| Dissolved Oxygen (mg/L) | 17.9 | 7.5 | 12.7 | - | - | 6.4 | 9.3 | 12.3 | 10.5 | 10.0 | 10.9 |
| Dissolved Oxygen Saturation (%) | 218 | 82 | 150.1 | - | - | 76.3 | 106.7 | 143.4 | 128.7 | 117.6 | 132.8 |
| Specific Conductivity (μS/cm) | 430.0 | 440.0 | 435.0 | - | - | 442.6 | 377.1 | 383.5 | 357.8 | 411.7 | 437.3 |
| Turbidity (NTU) | 7.2 | 26.3 | 16.8 | - | - | 35.1 | 103.5 | 22.8 | 42.5 | 26.7 | 27.1 |
| Chlorophyll a (μg/L) | 73.0 | 14.0 | 43.5 | - | - | 101.4 | 56.6 | 18.2 | 137.8 | 76.6 | 26.3 |
| Total Phosphorus as P (μg/L) | 104 | 151 | 127 | - | - | 169 | 257 | 164 | 197 | 174 | 251 |
| SRP as P (μg/L) | - | 36 | 36 | - | - | 27 | 117 | 7 | 24 | - | - |
| Total Nitrogen as N (mg/L) | 3.27 | 1.01 | 2.14 | - | - | 2.05 | 2.79 | 1.57 | 2.08 | 2.01 | 1.36 |
| (Phenate)Ammonia Nitrogen (NH3 + NH4+) as N (μg/L) | 16 | 361 | 185 | - | - | 215 | 203 | - | - | - | - |
| (Phenate)Ammonia Nitrogen (NH3) as N (un-ionized)(μg/L) | 2.5 | 20.9 | 11.7 | - | - | 16.9 | 13.7 | - | - | - | - |
| Nitrate + Nitrite (NO3 + NO2) as N (mg/L) | 1.76 | 0.97 | 1.37 | - | - | 0.50 | 1.31 | 0.12 | 0.15 | 0.78 | 0.12 |
| TN:TP ratio | 32 | 7 | 19 | - | - | 13 | 15 | 10 | 11 | 13 | 6 |
| pH | 8.9 | 8.2 | 8.5 | - | - | 8.2 | 8.4 | 8.9 | 8.9 | 8.2 | 8.4 |
| Alkalinity as CaCO3 (mg/L) | 197 | 206 | 202 | - | - | 185 | 162 | 123 | 168 | 189 | 209 |
| Silica as Si (mg/L) | - | - | - | - | - | 6.05 | 11.51 | 5.44 | 6.06 | - | - |
| Dissolved Organic Carbon (mg/L) | 3.77 | 5.66 | 4.72 | - | - | 4.93 | 4.94 | 11.15 | 11.32 | - | - |
| Inorganic Suspended Solids (mg/L) | 11 | 5 | 8 | - | - | 4 | 33 | 4 | 14 | 6 | 7 |
| Volatile Suspended Solids (mg/L) | 14 | 6 | 10 | - | - | 13 | 17 | 9 | 20 | 6 | 9 |
| Total Suspended Solids (mg/L) | 25 | 11 | 18 | - | - | 17 | 50 | 13 | 21 | 12 | 16 |
| Carlson Trophic State Index (Secchi)* | 63 | 70 | 66 | - | - | 69 | 73 | 64 | 62 | 58 | 62 |
| Carlson Trophic State Index (Chl a)* | 73 | 56 | 68 | - | - | 76 | 70 | 59 | 79 | 73 | 63 |
| Carlson Trophic State Index (TP)* | 71 | 76 | 74 | - | - | 78 | 84 | 78 | 80 | 79 | 84 |
| *Index values generally range between 0 and 100, with increasing values indicating more eutrophic conditions. |