Delineating Recharge to a River Valley Aquifer by Riverine Seismic and EM Methods
Why this work is in the frame
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Bibliographic record
Abstract
The City of Fredericton, New Brunswick, Canada operates a water well field adjacent to the Saint John River. Water is extracted from a semi-confined aquifer that consists of a buried sand and gravel esker ridge discontinuously covered by a clay∕silt aquitard. Geological, hydrogeochemical, and hydraulic data have long pointed to infiltration of river water as the main source of aquifer recharge but the shape and size of the recharge zone has, until recently, remained speculative. A combination of three geophysical surveys, including resistivity imaging along the shoreline, and seismic and electromagnetic profiling on the river itself, have now revealed the complex outline of the area beneath the river where the infiltration likely occurs. Broadband seismic reflections, with dominant frequencies of 2.5kHz were recorded from depths as great as 50m using a boomer source and 1KB Seistec line-in-cone receiver well suited to operation in the shallow water environment. EM31 and EM34 terrain conductivity meters, deployed in an outboard-motor-powered canoe and raft, revealed the subsurface conductivity structure in the same depth range. While the seismic method imaged the clay aquitard stratigraphy including its termination against the esker ridge, the electromagnetic method provided a more complete plan view of the extent of the clay window recharge zone. The two riverine data sets are highly complementary; as a start towards joint interpretation, we introduce the concept of bathymetry-corrected apparent conductivity and show how it helps to sharpen the boundary of the inferred recharge area. Confirmation of the geophysical interpretation is provided by the presence or absence of aquitard material in boreholes that have recently been drilled from a barge on the river.
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Full frame distilled prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. Learned from the 10,348 direct Codex labels and 10,348 direct Gemma labels. Candidate is the union of thresholded teacher heads; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels or direct frontier model labels.
Codex and Gemma teacher scores by category
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.000 | 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 it