Unusual drawdown curves for a pumping test in an unconfined aquifer at Lachenaie, Quebec: field data and numerical modeling
Bibliographic record
Abstract
An unconfined aquifer was instrumented with monitoring wells over a surface area of about 100 m × 100 m. The aquifer is a sand deposit overlying a thick nonfissured layer of Champlain Sea clay. The paper presents the results of a pumping test at a constant flow rate. None of the curves of drawdown versus time presented the S shape of current theories; however, all drawdowns indicated that the aquifer was homogeneous. The values for the specific yield were too low and varied with distance and time instead of being constant. The theories for steady and unsteady states provided different values for the saturated hydraulic conductivity. To understand the field behavior that differs from theoretical predictions, the pumping test conditions were modeled numerically using a finite element method. The transmissivity was derived from the Dupuit equation, and different curves for capillary retention and unsaturated permeability were examined. The numerical drawdowns agree with the experimental drawdowns. Several numerical models were investigated. All of them solved the inverse problem correctly for steady-state conditions and fairly well for transient conditions with highly nonlinear characteristic functions. The best solution to the transient problem was obtained using trial and error, by considering how the drawdown curves might be modified due to anisotropy and stratification. According to these field tests and the numerical analysis, the S shape is not the rule, and a different shape can be perfectly normal due to the complexity of unsaturated flow.Key words: pumping, unconfined aquifer, permeability, drawdown, numerical modeling.
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.001 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.001 | 0.001 |
| Science and technology studies | 0.001 | 0.001 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.001 | 0.000 |
| Research integrity | 0.001 | 0.000 |
| Insufficient payload (model declined to judge) | 0.001 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one source (direct Gemma or distilled Codex), not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".