Nitrogen Loading Calculator

Work out nitrogen loading instantly with clear inputs, formula shown and shareable results.

About Nitrogen Loading Calculator

Nitrogen load is flow times concentration, and annualising it lets the discharge be compared against a catchment loading target expressed in kilograms per hectare per year. Nutrient-sensitive catchments often operate loading caps or trading schemes, so headroom rather than concentration determines whether growth can be accommodated.

Formulas

Nitrogen load

Load (kg/day) = flow x total N / 1000; annual = daily x 365

Area loading

Area loading = annual load / catchment area

Worked example

With the default values below, Nitrogen Loading Calculator returns Annual Nitrogen Load of 82,125.0. Change any input above and every figure here is recalculated in your browser.

Inputs used

Flow Rateminimum 0 m3/day: 5,000 m3/day
Total Nitrogenminimum 0 mg N/L: 45 mg N/L
Receiving Catchment Areaminimum 0 ha: 2,500 ha
Target Area Loadingminimum 0 kg N/ha/year: 20 kg N/ha/year

Results

Annual Nitrogen Load: 82,125.0
Daily Nitrogen Load: 225.000
Area Loading Rate: 32.8500
Headroom To Target Loading: -32,125.0

Step by step

1Values used
2Nitrogen load
3Area loading
4Annual Nitrogen Load= 82,125.0
5Daily Nitrogen Load= 225.000
6Area Loading Rate= 32.8500
7Headroom To Target Loading= -32,125.0

Assumptions and limits

The result is derived only from the 4 inputs listed above. Anything not among them is not part of the calculation.
In particular, this calculator does not take inflation, tax or compounding frequency into account.
Figures are rounded for display to 4 decimal places, so totals built from several rounded parts can differ slightly from the unrounded arithmetic.
Catchment nutrient budgets and neutrality requirements are set by environmental regulators and planning authorities. Confirm the applicable methodology.

How these calculators are built and tested is described on the Methodology page. If a figure looks wrong, please report it.

Catchment nutrient budgets and neutrality requirements are set by environmental regulators and planning authorities. Confirm the applicable methodology.

Frequently Asked Questions

Why express loading per hectare?

Because eutrophication risk relates to nutrient input per unit of catchment or waterbody area. It allows point and diffuse sources to be compared on a common basis.

What is nutrient neutrality?

A requirement that new development must not increase catchment nutrient load, met by offsetting through treatment upgrades, land use change or credit purchase. It has become a binding constraint on housing in some sensitive catchments.