Global groundwater environmental flow violations
Bibliographic record
Abstract
Groundwater serves as a vital resource to meet growing freshwater demands, particularly for the irrigation sector, driven by population growth and socioeconomic development. Apart from this application, however, groundwater also supports surface water bodies through groundwater discharge. While irrigation demands are important, environmentally safe levels of groundwater discharge must also be maintained.We applied two methods of calculating groundwater environmental flows using modelled groundwater discharge. The first, Presumptive Standard1, stipulates that 90% of naturally occurring groundwater discharge should be maintained. The second, Q902, considers the 90th percent exceedance from a 60-month moving window as the environmental flow. We then calculated violations when the human-impacted groundwater discharge, accounting for sectoral water use, dropped below the environmental flows.At the river basin scale, we assessed violation frequency and severity. Notably, despite Presumptive Standard violations occurring more frequently than Q90 violations, both methods identified the same spatial trends: basins in intensively irrigated regions experienced the most frequent and severe violations.Similarly, we assessed the frequency and severity of violations during low-flow periods, isolated using the Q90 as a low-flow threshold, when the role of groundwater to support surface water bodies increases. During these critical instances, the Presumptive Standard and Q90 estimated nearly identical violation schemes.The groundwater environmental flow violations were further compared to surface water environmental flow violations, following the methodology of Variable Monthly Flow3. This comparison highlighted the importance of including groundwater in environmental flow assessments, as many regions experience high levels of groundwater violations compared to surface water violations.In addition to frequency and severity, we assessed the timing of violations in select basins with high levels irrigated agriculture. Timing refers to the specific instances when violations occurred. This analysis showed the progression of violation trends over time and emphasized the driving force of groundwater abstractions on environmental flow violations.Our study shows that including groundwater in assessments of environmental flows is vital, as groundwater is a finite source which plays a crucial role in supporting surface water bodies. When conducting such an assessment, however, the selected groundwater environmental flow threshold may have an effect. If all timesteps are to be considered, the choice of methodology between the Presumptive Standard and Q90 will make a difference. If the focus is on low-flows, however, the choice of methodology will not greatly impact the assessment.1. Gleeson, T. & Richter, B. How much groundwater can we pump and protect environmental flows through time? Presumptive standards for conjunctive management of aquifers and rivers. River Res Appl 34, 83-92 (2018).2. de Graaf, I. E. M., Gleeson, T., (Rens) van Beek, L. P. H., Sutanudjaja, E. H. & Bierkens, M. F. P. Environmental flow limits to global groundwater pumping. Nature 574, 90-94 (2019).3. Pastor, A. V., Ludwig, F., Biemans, H., Hoff, H. & Kabat, P. Accounting for environmental flow requirements in global water assessments. Hydrol Earth Syst Sci 18, 5041-5059 (2014).
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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 | 0.001 | 0.002 |
| Meta-epidemiology (narrow) | 0.001 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.001 |
| Bibliometrics | 0.003 | 0.006 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.001 | 0.001 |
| Open science | 0.000 | 0.002 |
| Research integrity | 0.001 | 0.000 |
| Insufficient payload (model declined to judge) | 0.003 | 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".