“[.] And we are fundamentally inclined to claim that the falsest judgments [...] are the most indispensable for us; that without accepting the fictions of logic, without measuring reality against the purely invented world of the unconditional and self-identical, without a constant falsification of the world by means of numbers, man could not live. That renouncing false judgments would mean renouncing life and a denial of life.
To recognize untruth as a condition of life; that certainly means resisting accustomed value feelings in a dangerous way; and a philosophy that risks this would by that token alone place itself
beyond good and evil.”
www.betami.com.br Back-and-Front-end MODFLOW | PEST Management Platform
First things first:
- How a PEST derived numerical model looks like for us, mere mortals which do not excel in maths and computer science?
Topography; 3D GRID; Numerical horizontal end vertical discretization's
To build a mathematical, numerical groundwater model we also need the targets:
Hydraulic Heads (H), and a couple expected boundary conditions fluxes:?
Targets: Hydraulic Heads (m) and boundary conditions fluxes (m3/d) ... to be pursued
For boundary conditions we pick 23 even distributed drains DRN; 21 General Heads GHB; 30 Streams SRT; Plus 22 pilot points of recharge RCH, 16 EVPT and 36 hydraulic conductivities (K), + anisotropies (HANI | VANI). Then also 21 fixed Constant Heads CHD and, sure enough, the 18 pristine hydraulic Heads.
By practical experience, it can be said that all sensibilities must be very low. The only way to reach a even distributions throughout the model. But these sensibilities must not be too low (or bad located, or conceptually inappropriate, or numerical impractical, and so on… ), at the point of not making any difference at all (for the automated engine in charge of choosing these variables).
Only a well balanced sun of all the variable’s sensibilities “or susceptibilities” guarantees a unbiased solution.
14 pages or so covers all the “basics” of a groundwater model exercise done by PEST automatizations. It comes from a synthetic example extensively described at a couple of GMDSI tutorials. https://gmdsi.org/education/tutorials/
PEST parameters selection’s https://www.betami.com.br/12-the-jacobian-matrix
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