EcoGuardian / Grant
Nutrient Calculator
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Advanced Stormwater Runoff Nutrient Calculator
This calculator preserves the original website’s arithmetic. Its area input is labeled hectares, but its runoff formula does not convert hectares to square meters. The nutrient coefficient units also do not reconcile with the reported loads. Results are retained for comparison and are not validated design estimates.
Calculation Results
Enter your land use, area, and annual rainfall to compare the original model’s outputs.
- Annual Runoff Volume
- m³
- Total Nitrogen Load
- kg/year
- Total Phosphorus Load
- kg/year
Annual Nutrient Load Comparison
Total Nitrogen
Total Phosphorus
Nutrient Load (kg/year)
Nutrient Coefficient Reference Table
| Land Use | Nutrient | Coefficient Value | Range |
|---|---|---|---|
| Forest | Total Nitrogen | 1.2 kg/ha/year | 0.8 - 1.6 |
| Forest | Total Phosphorus | 0.04 kg/ha/year | 0.02 - 0.06 |
| Agriculture | Total Nitrogen | 5.2 kg/ha/year | 3.5 - 6.9 |
| Agriculture | Total Phosphorus | 0.3 kg/ha/year | 0.2 - 0.4 |
| Urban | Total Nitrogen | 7.8 kg/ha/year | 5.2 - 10.4 |
| Urban | Total Phosphorus | 0.8 kg/ha/year | 0.5 - 1.1 |
Original formulas and model notes
Runoff volume = (rainfall ÷ 1000) × area × runoff coefficient.
Nitrogen load = runoff volume × nitrogen coefficient. Phosphorus load = runoff volume × phosphorus coefficient.
Runoff coefficients: Forest 0.2; Agriculture 0.3; Urban 0.7. Original coefficient values and ranges are retained above. Empty, negative, and non-finite inputs are rejected.