The footprint of global change shows up in multiple indicators. As evidence accumulates, some paradoxes also emerge. At multiannual time scales, one intriguing aspect is why some ecosystems seem to follow more closely indicators of general atmospheric dynamics (e.g., CO₂ increase, hemispheric mean annual temperature) than the local weather and deposition records. Pathways of mechanistic causality must exist that explain the apparent paradox. Probably, they are related to processes of a different characteristic reaction and renewal times. One of the systems in which the phenomenon has been observed is the plankton of remote lakes. The TRANSFER project aims to address this issue.

In recent years, the notion known as the ‘old water paradox’ has gained strength: in headwaters catchments, stream discharge responds in minutes to hours to the storms, but runoff water is aged months to years.

Geophysical techniques provide virtual images of the subsoil that allow us to infer the structure of the geological materials and assess the presence of underground water. In the TRANSFER project, we have counted on the expertise and cooperation of the group on Environmental and Economic Geology and Hydrology (GEAH) of the University of Barcelona and B&B Geòlegs consulting to obtain profiles of the terrain by Electrical Resistivity Tomography (ERT).

The isotopes of water (deuterium, tritium and ¹⁸O) can be used to determine the “age” of water, that is, the time water spends in the catchment in average since it is deposited as rain or snow, the so called mean residence time (MRT). Despite hydrograms show that the amount of water falling on the headwater catchments in the National Park during a storm is drained out in just three or four days, and that the bulk of the seasonal snowcover melts in two or three months, we have estimated (from previous deuterium and ¹⁸O measurements) that the MRT of water is of the order of one year or longer in these alpine catchments.