THE ROLE OF GEOPHYSICS IN CHARACTERIZING THE HYDROLOGIC SETTING OF HYDROLOGIC OBSERVATORIES

CUAHSI’s plan for a network of large-scale hydrologic observatories requires a thorough assessment of the hydrologic setting of each representative catchment. In responding to a recent informal poll by CUAHSI (see the url below), the geophysical community has identified a number of areas where it might contribute, ranging from broad reconnaissance studies to detailed site investigations. While most hydrologists are familiar with the application of geophysics to groundwater investigations, recent progress has been made in applying geophysics to surface water runoff studies as well.

Profound contributions can be made to identifying the hydrologic constraints on a field problem through relatively straight-forward geophysical applications – such as seismic, ground penetrating radar (GPR), electromagnetic, DC resistivity, gravity and magnetic methods – particularly when using multi-disciplinary approaches. A general feeling is that much can be gained from putting these “standard” tools into the hands of more people, and making the techniques generally accessible to non-specialists and specialists alike. To do so, one needs to consider the trade-off between industry\national lab\university collaborations on one hand, and the combination of university-based centralized and distributed facilities on the other. Does the hydrologic community need a single “expert” central facility, or would it be best served by nurturing ties among the broadest range of interested collaborators – some local, some regional, some national, some international?

Preliminary site characterization of a potential hydrologic observatory is only the first step. Geophysics can, and should, be used in on-going programs to monitor time-dependent hydrologic variables, from near surface soil moisture to the integrated volume of water in an aquifer. Geophysics provides a natural means to aggregate data that are typically limited spatially (such as soil moisture measurements with a tensiometer or aquifer characteristics from a monitoring well) to the large scale required for the network of observatories envisioned by CUAHSI.

A synopsis of comments from a number of geophysicists can be found at: http://www.geo.brown.edu/research/Hydrology/CUAHSI_Geophysics_HMTF/