Groundwater dynamics and surface water-groundwater interaction in a prograding delta island, Louisiana, USA
Bibliographic record
Abstract
Delta islands make up the majority of coastal delta area. However, the groundwater hydrology of young, prograding delta systems and its relationship to surrounding surface water dynamics are poorly understood. Deltas in coastal environments are assumed to function as chemical “buffers”, filtering nutrient-rich terrestrial runoff through the island structures and surface water ecosystems as it travels to the sea, but the magnitude of this effect cannot be accurately quantified without understanding the physical relationships between the surface water and groundwater. This study developed the first conceptual model of the hydrology of prograding delta island groundwater systems. The study was based on field data collected at Pintail Island, a 2 km2 island within the Wax Lake Delta in Louisiana. Hydraulic properties and processes were quantified at multiple depths at locations spanning the island elevation gradient. Groundwater and surface water levels were monitored. A weather station recorded precipitation, air, and wind conditions. The groundwater within Pintail Island was both spatially and temporally dynamic throughout the study period of Sept/9/2013 to Feb/4/2014. The aquifer within the distal limbs of the island responded as a connected, saturated unconfined aquifer. The portions of Pintail Island within the older, proximal, higher elevation apex were found to be a two-layer system with fine sediments and organic matter overlying sandy deposits. The aquifer within this section of the island responded differently during times of elevated surface water (storm events) and times of normal surface water (calm periods) and differently from the distal-island unconfined system. The fine, shallow (roughly 0-60cm depth) sediments capping this older, higher portion of the island appeared to inhibit vertical flow between the surface and subsurface, creating semi-confined conditions within the sands in the deeper island subsurface. High water levels led to overpressurization of the apical aquifer, which was maintained between storms due to the low hydraulic gradient and the low permeability of the porous medium. During inundating storm events, groundwater potentials mimicked surrounding surface water levels. This conceptual model of a prograding coastal delta island now provides a foundation for further, hydrologically-realistic study of delta ecology and nutrient exchange.
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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 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.001 |
| Science and technology studies | 0.001 | 0.000 |
| Scholarly communication | 0.001 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.002 | 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".