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sci.eutrophication-Vollenweider Calculator
Calculates lake phosphorus loading, predicted concentration, and trophic state using Vollenweider's empirical model and OECD criteria. Critical phosphorus loading beyond which lakes eutrophy = 0.6 g P/m²/yr (Vollenweider) — Shagawa Lake (Minnesota) restoration achieved oligotrophic status after reducing external P load by 87%.
Inputs
P In Mg L
Reference formula or conversion factor shown for context.
Q M3 Yr
Reference formula or conversion factor shown for context.
V M3
Three-dimensional space occupied (m³ or L). 1 m³ = 1,000 L.
Sigma Sed
Speed in a specified direction (m/s). Required for momentum, kinetic energy, and wave calculations.
Results
equilibrium P concentration (mg/L)
The proportional relationship between two quantities.
hydraulic retention time τ (years)
The computed duration or time value.
surface overflow rate qs (m/yr)
Flow rate Q — the volume of fluid passing a point per unit time.
phosphorus load (g/m²/yr)
pH of the solution. Below 7: acidic. 7: neutral. Above 7: basic (alkaline).
Vollenweider 1975: P_eq = P_in/(1 + σ/qs)
Sample size or count used in the calculation.
trophic state
pH of the solution. Below 7: acidic. 7: neutral. Above 7: basic (alkaline).