So they support the idea that Mars had an active hydrological system back then; long-term contact with water is needed for the formation of clays.

This hydrological system is inter-twined with a regional flow systems not bound by the morphological limits of the moraine.

Switzerland has a varied and complex hydrological system.

This hydrological system is extremely vulnerable to pollution because of the very high permeability of the carbonate aquifer.

The combined flow was then estimated at 40 million cubic meters, making it one of the largest hydrological systems in Canada.

The chateau stands in good order today, and although the park and its follies have been neglected, the extensive hydrological system still functions.

These lakes form a hydrological system that is unique in the earth's deserts.

The mountains within the park are also managed within this conservation philosophy in order to preserve the hydrological system that feeds the springs.

Its aim is to conserve and make the best use of the whole hydrological system by viewing it as a unit.

It seems to be of paramount importance to understand the old hydrological systems, if they are to be properly restored.