Groundwater is an essential component of the hydrological cycle, which behaves slowly, thus providing long-term water storage and subjected to slow evolution. In practice results can be largely irreversible in the case of large aquifers and thick unsaturated zones. Through the interaction with surface water it is a key component to many ecological systems of relevant social and economic value, but also an important water resource for humans and their activities. Both aspects have to be combined to get the maximum social benefit in the long-term, which means that they cannot be maximized separately from the others.
The European Water Framework Directive of 2000 and the so called Groundwater Daughter Directive of 2006 have as a main objective the good ecological status of the Earth’ water bodies and this has to be accomplished in the so defined water bodies. This may be clear for surface water but is more difficult for groundwater, especially because their environmental role is complex, anthropic effects are highly delayed, and the aquifers may and should play the role of natural infrastructures to increase and guarantee the availability of water resources for humans, especially in droughts. The concepts of water heritage, water resource budget in quantity and quality, and loss of them by passive accumulation from human activities has been rarely made explicit with a long-term perspective.
A revised extension of the Water Framework Directive should consider the role of aquifers as natural manageable infrastructures, whose use may be accompanied by some limited environmental loss when there is a positive social benefit, in the same way that the land can be occupied for urban expansion, transportation or surface water storage in dams. This may be associated with some controlled and managed degree of groundwater level drawdown, wetland reduction, increased cost of groundwater abstraction, water quality changes relative to the natural situation, seawater intrusion in coastal aquifers, land subsidence, water reserves decrease, etc. To consider this, a redefinition of the good status has to be worked out, which is especially needed in the southern areas of Europe.
Other aspect to be considered more in detail is the delayed effect of water transfers, irrigation or land drainage, which may greatly alter aquifer recharge and consequently the full water system. The water system will evolve slowly, often only perceived with good monitoring and adequate interpretation. Large passives of pollutants may cumulate, making recovery unfeasible. So, aquifers need different qualification of the status and protection according to their human water supply, environmental and security role. In these aquifers should be imposed adequate standards of well construction to prevent the entry of pollutants. Some difficult to recover aquifers should have reduced requirements, but considering externalities and how to compensate them.