Prepared under the Support of The National Aeronautics and Space Administration Grant NAG 5-134This work develops a simple, second-order parameterization of the water fluxes at a landsurface for use as the appropriate boundary condition in general circulation models of the global atmosphere. The derived parameterization incorporates the high non-linearities in the relationship between the near-surface soil moisture and the evaporation, runoff and percolation fluxes. Based on the one-dimensional statistical-dynamic derivation of the annual water balance developed by Eagleson (1978), it makes the transition to short term prediction of the moisture fluxes, through a Taylor expansion around the average annual soil moisture. A comparison of the suggested parameterization is made with other existing techniques and available measurements. A thermodynamic coupling is applied in order to obtain estimations of the surface ground temperature.