No abstract

A method for obtaining pointwise or spat•lly averaged estimates ofa nonintrinsicfunction is introduced based on residual kriging. The method relies on a stepwise iterative regression proeess for simultaneously estimating the global drift and residual semivariogram. Estimates of the function are then obtained by solving a modified set of simple kriging equations written for the residuals. The modification consists of replacing the true variogram in the kriging equations by the variogram of the residual estimates as obtained from the iterative regression process. The method is illustrated by considering groundwater levels in an Arizona aquifer. The results are eompared with those obtained for the aquifer by the generalized covariance paekage BL UEPA CK-3D.

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Abstract. Recent work has emphasized development of full-range water-retention functions that are applicable under both wet and dry soil conditions, but evaluation of such functions in numerical modeling has been limited. Here we show that simulations using the Rossi-Nimmo (RN) full-range function compared favorably with those using the common Brooks-Corey function and that the RN function can improve prediction of water potentials in near-surface soil, particularly under dry conditions. Simulations using the RN function also improved prediction of temperatures throughout the soil profile. Such improvements could be important for calculations of liquid and vapor flow in near-surface soils and in deep unsaturated zones of arid and semiarid regions.

In part 1 of this paper a new, statistically based approach to the problem of estimating patially varying aquifer transmissivities on the basis of steady state water level data was presented. Part 2 describes a case study in which the new method is applied to actual field data from the Cortaro Basin in southern Arizona. The paper does not present a perfect example of how the new inverse method should be used but only a preliminary demonstration of some of its capabilities in dealing with realistic data. The estimated transmissivities are shown to compare favorably with those obtained earlier for the same basin by an ad hoc trial‐and‐error procedure. Both sets of transmissivity values have been used successfully in conjunction with a mixed explicit‐implicit finite element model to reproduce 25 years of water level variations in the Cortaro Basin in response to pumpage during the period 1940–1965. The finite element model has revealed some important features of the local hydrogeological regime which have not been recognized previously.