For example, abstraction charge rates are higher for domestic users while volumes abstracted for drinking w'ater supply are much lower than volumes abstracted for irrigation purposes. The pressure exerted on the resource can also be assessed through the difference between the volumes of water that are abstracted and the volumes that are returned to the environment. For example, it is estimated that around 90% of the volume used for cooling thermal and nuclear power plants is returned to the w'atercourse, w'hile irrigation returns a small portion of its abstracted volume to the environment. The latter explains why rates for cooling purposes are quite low compared to other uses, but does not explain why rates for irrigation are low'er than rates applied to drinking water supply, know'ing that almost all volumes used by households are returned to the environment after treatment.