Groundwater-surface water interaction in Frenchman's Bay watershed, Ontario: implications for urban recharge, contaminant storage and migration
Bibliographic record
Abstract
Urban development has, historically, been more concerned with the hydraulic characteristics of the drainage systems and technological solutions for controlling floods and pollution than understanding the hydrological characteristics and sustainability of urban catchments. Given the complexity in evaluating the hydrologic behaviour of urban catchments, these systems remain poorly understood and an under-researched field of hydrogeology. Conventional models that solely concentrate on urban runoff as the primary cause of reduced natural recharge do not effectively deal with new sources or pathways of recharge created specifically by urbanization. The hydrologic cycle of Frenchman's Bay watershed, a 27 km2 highly urbanized catchment just east of Toronto, Ontario, Canada has undergone a fundamental change in the last 50 years due to increased urban cover. Isotopic hydrograph separation of groundwater and surface waters in stormflow showed that only about 15% of rainfall appears as overland flow and that groundwater accounts for 21% of the total stormflow. Furthermore, it was estimated that 35% of the total rainfall contributes to groundwater recharge. Analytical and numerical models were used to quantify and validate the elements of the urban water cycle. A modified soil moisture balance for the watershed highlighted the significance of localized recharge through preferential pathways. It was found that localized recharge through bypass flow has increased net recharge by about 36%. Moreover, infiltration of roof runoff and physical losses from water mains have essentially maintained urban recharge at preurban levels. Numerical simulations verified increased recharge that occurs following urbanization through onsite infiltration of roof runoff and bypass flow. A chloride mass balance revealed that approximately 50% of road salt applied to the catchment is stored in the shallow subsurface. The presence of oxygen-18 depleted groundwaters with higher bicarbonate concentrations in the most urbanized part of the catchment further substantiates the existence of a highly responsive urban aquifer. The findings of this study have important implications in our understanding of the complex behaviour of urban aquifers including groundwater-surface water interactions and contaminant flow paths.
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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 | 0.001 |
| Scholarly communication | 0.001 | 0.000 |
| Open science | 0.001 | 0.000 |
| Research integrity | 0.000 | 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".