Applied to deal with pollution problems and can be adapted to manage groundwater when individual withdrawals cannot be noticed. The tax approach assumes that consumption can be influenced by the cost of water supply. If water abstraction is metered an inidivdual tax system (Pigouvian) can be used. If asbtraction points are unknown or if the water is unmeterd, the regulator can charge all actors using groundwater with an ambient tax with level proporitnal to the over-exploitation level. The regulator can assess the abstraction level based on simple observations of groundwater levels or using groundwater models. Each user is then charged with the same tax level irrespective of their actual groundwater consumption.