Summary
CATHERINE, developed by the BRGM, analyses simultaneous variations in the levels of a river and an adjacent aquifer.

CATHERINE is an acronym of "CAlcul THEorique de l’influence d’une RIvière sur des NIveaux de nappe" (Theoretical calculation of river influence on groundwater levels).

## CATHERINE functions

CATHERINE offers a simple means of performing the following operations:

For an aquifer with a rectilinear boundary (river, lake or sea) whose level varies over time:

• To calculate the hydraulic diffusivity of an aquifer from monitoring of  simultaneous variations over time of the piezometric level at a given point in the water table and the water level in a river, lake or sea. If the storage coefficient is known, transmissivity (and permeability) can be deduced. Conversely, if the transmissivity is known, the storage coefficient can be deduced.
• To calculate variations in the piezometric level at a given point in an aquifer with known diffusivity and bounded by a river, lake or sea where the  variations in height over time are known.
• To correct a piezometric level for water level variations due to tides, to the passage of a flood or to a dam release. The corrected piezometric level can then be used to interpret a pumping test or to model the relationship between rainfall and water level.

For energy transfer calculations, the following operations can be performed:

For an aquifer or soil area with a rectilinear boundary (river, lake or sea) whose temperature varies over time:

• To calculate the thermal diffusivity of an aquifer from monitoring of the simultaneous variations over time of the temperature at a given point in a heat-conducting medium (e.g. soil or immobile groundwater) and the temperature at a boundary. If the thermal conductivity is known, the calorific capacity can be deduced. Conversely, if the calorific capacity is known, the thermal conductivity can be deduced.
• To calculate temperature variations at a given point with known thermal diffusivity and where the temperature variations of the boundary are known. Thermal variations in a soil area can then be worked out from changes in the surface (or air) temperature.
• Correction of temperature variations due to temperature variations on a soil surface. The corrected temperatures can then be used to analyse the efficiency of a heat storage facility.

The analytical solution method is very easy to apply.

CATHERINE can determine the parameters to be used with the MARTHE application.