The hydroelectric coupling generating self-potential anomalies recorded on the Earth's surface has received a considerable attention in the last four years. Geophysical applications include the use of this phenomenon for mapping subsurface fluid flow, the study of hydrothermal activity, and the use of self-potential anomalies to monitor volcanic activity and the possibility, still debated, of seismic activity forecasting through the use of electromagnetic precursors of electrokinetic nature. We model here two key-parameters relevant of the hydroelectric coupling in clayey porous rocks. These two parameters are the &zgr;-potential and the specific surface conductivity, which depend on the electrochemistry of the pore water/mineral interface. They are modeled in the case of a kaolinite saturated by a NaCl brine using a triple layer model (TLM) in which the parameters are optimized using the Simplex algorithm. ¿ 2001 American Geophysical Union