Which of the following is a renewable natural resource?

Concept

A renewable resource is replenished by natural processes on a timescale relevant to human use.

A non-renewable resource forms so slowly that its stock is effectively finite on that timescale.

Application

Ground water is replenished when precipitation infiltrates soil and rock as part of the hydrological cycle. Subject to sustainable withdrawal, it therefore fits the renewable-resource criterion.

Contrast

• Petroleum forms from ancient organic matter over geological time and is depleted far faster than it is replaced.

• Natural gas is a fossil fuel formed over geological time, so its reserves are finite on a human timescale.

• Coal develops from buried plant matter over millions of years, so consumption exhausts it far faster than it can form.

Cross-check

Applying the replenishment-timescale test separates ground water from the three fossil fuels.

Therefore, ground water is the renewable natural resource among the choices.