To reach sustainable levels of use of a natural resource, the
appropriation of that natural resource should not be higher than
the natural regeneration rate (Eder and Narodoslawsky, 1999).
Translating this principle to water use is straightforward for
groundwater. The withdrawal of groundwater should not exceed
the groundwater recharge rate so that groundwater levels do not
drop due to human activities. For rivers, this principle involves
ensuring that sufficient water is left for environmental flows and
related ecosystem services.
Godfrey and Todd (2001) provide a particularly vivid representation
of the sustainable use of water in both a qualitative and