Rui Hugman

Non-Linear Uncertainty Analysis

In contrast to linear uncertainty analysis, non-linear methods do not suffer from the limitation of assuming a linear relationship between model predictions and model parameters. Given that such relationships are rarely linear, this is an important consideration. Nevertheless, non-linear methods are not free of assumptions, can sometimes incur a higher implementation cost than linear methods, […]

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Covariance Matrices: The PPCOV Suite

A variance-covariance matrix, often referred to as a covariance matrix, is a square matrix that provides covariances between pairs of elements of a random vector. A covariance matrix of model parameters describes the variance of each parameter and the covariance of that parameter with that of every other parameter. For cases in which parameters represent points

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Linear Uncertainty Analysis

Linear uncertainty analysis is also known as “first order second moment” (or “FOSM”) analysis. It provides approximate mathematical characterisation of prior predictive probability distributions, and of posterior parameter and predictive probability distributions. It has other uses as well. It can be used to demonstrate how the history-matching process bestows worth on data. It can also

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How Complex Should a Groundwater Model Be? by Catherine More and John Doherty Because environmental systems are complex, models must be complex too. Otherwise, how can they simulate the impact of human management on natural systems? This applies especially to groundwater systems. After all, water flows through heterogeneous media and interacts with surface water bodies in complex ways. This line of

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OLPROC: Processing Observations Made Easy

OLPROC is a model dancing partner. Its role is to postprocess model outputs in order to match them with field measurements, as well as to assist in automatic creation of PEST input datasets involving complex, multi-component objective functions. Starting from a set of field measurement data and model output files, this tutorial demonstrates how OLPROC

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Worked Example: Simultaneous Interpretation of Six Pumping Tests

Simultaneous fitting of drawdowns induced by pumping at multiple sites in an area of complex geology revealed important patterns of connected permeability Over a six month period in July 2014, BHP conducted six pumping tests of between 5 and 11 days duration near the site of its OB31 pit in the Pilbara region of Western

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