Simulation of Large-Scale Field Infiltration Experiments Using a Hierarchy of Models Based on Public, Generic, and Site Data

Abstract

mental safety assessment in common situations where time and resources are severely limited. Comparative simulations of a large-scale field infiltration experi-As the question is quite broad, we narrowed it down ment at the Maricopa Agricultural Center (MAC) near Phoenix, AZ, were conducted using a hierarchy of models based on public, generic, by asking what is the ability of simple models and relaand site data joined with pedotransfer functions and an inverse procetively inexpensive data to reproduce and predict reliadure. Our purpose was to investigate the ability of simple models and bly the time evolution of water content profiles in nine relatively inexpensive data to reproduce and predict reliably the time 10-m-deep neutron monitoring boreholes during largeevolution of water content profiles in nine 10-m-deep neutron moniscale infiltration experiments at the MAC near Phoenix, toring boreholes at the site. By relying solely on public sources of in-AZ? To address this narrower question, we conducted formation one might conclude that soil at the MAC site is uniform to comparative simulations of the experiments, using moda depth of 16 m, with a water table at about 22 m. Upon collecting soil samples at the site, we learned the soils are layered and laterally els of increasing complexity and a hierarchy of supportdiscontinuous, with a perched water table at about 13 m. To identify ing data. The fastest and least expensive way to assess the least level of complexity required to simulate infiltration at the the geologic makeup and hydraulic properties of a site MAC, we compared models that consider one-and two-dimensional flow is to rely on public sources of information coupled with in a uniform soil, a soil consisting of uniform layers, and a stratified generic databases. Such information and data seldom soil with laterally distinct zones. There is a paucity of hydraulic characsupport more than a very simple model of the site. A terization data for the site. To investigate the feasibility of obtaining more accurate but time-consuming and costly approach hydraulic parameter estimates for the models on the basis of soil type, we ascribed uniform properties to each layer or zone using mean values is to describe site geology on the basis of disturbed soil of three generic databases. To improve these estimates, we ascribed samples collected at the site and to assess their hydraulic variable soil hydraulic properties to individual soil samples using reproperties using pedotransfer functions. This may justify gression and neural network pedotransfer functions based on soil type the postulation of a more detailed site model. Even and bulk density; we then used them to obtain Bayesian updates of more accurate but demanding and expensive is to collect mean hydraulic properties in each layer or zone. We used the various relatively undisturbed soil samples for laboratory determodels and mean parameter estimates to simulate water contents mination of their hydraulic properties. Additional alterduring one of several infiltrati...

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