TOPMODEL, a simple physically based conceptual model, has been widely applied to various water resource investigations. Previous studies of the hydraulic transmissivity function with depth indicate that an exponential function alone may not be appropriate. Recent work suggests that a first-order hyperbolic function can provide improved simulations of base flow recession in the context of TOPMODEL. We present a generalized power function for a range of possible cases and apply this function to the TOPMODEL concepts. The specific function that is most applicable is location dependent.¿ 1997 American Geophysical Union