Influence of Subsurface Pipe Perforations on Transient Water Table Response and Steady Soil-Water Flux under Subirrigation
Bibliographic record
Abstract
Highlights Water table rise was slower under a sparsely perforated pipe as compared to a pipe that was densely perforated. Response time increased as buried pipe depth decreased for both combinations of perforation characteristics. Fluxes from buried pipes spaced at 15 m in loamy sand satisfied the water demand for cereal/grain crops (6 mm d -1 ). Increasing perforation density on the pipe wall is the most effective way to reduce exit head losses. Abstract . It is important to consider the water table rise into the unsaturated zone when designing subsurface irrigation systems that consist of buried perforated corrugated pipes. Corrections to pipe spacing equations for head losses due to perforations are based on the entrance resistance, which is derived for buried pipes operating in drainage mode. However, the boundary condition at the soil-pipe interface when operated in subsurface irrigation mode requires the use of the exit resistance to accurately account for perforations in the pipe wall. Simulations of a subsurface irrigation system with four soil textures, three lateral pipe spacings, and three buried depths were carried out, with the numerical model COMSOL, to demonstrate the effects of variable perforation characteristics on the transient water table rise into the unsaturated zone. Soil-water fluxes were also computed for the system when operated under steady-state conditions. The simulated water table rise exceeded or approached a predetermined target water level of 1.65 m above the buried pipes in coarse-textured soils (loamy sands and silt loams) with lateral pipe spacings as large as 10 m. Increasing the number and length of rectangular slots in the pipe wall (densely perforated) can reduce the water table response time to reach the target level by 15 h in a silt loam soil and 25 h in a clay soil. The optimum pipe spacing needed to sustain a soil-water flux of 6 mm d-1 (common to eastern Canada and the U.S. Midwest) can be increased from 15.1 to 16.2 m in loamy sands by using densely perforated pipes. In contrast, increasing perforations in pipes buried in clays and sandy clays will result in pipe spacing increases of less than 0.2 m because these fine-textured soils have lower hydraulic conductivity. This study has demonstrated that variable perforation characteristics can be included in the analysis and design of subsurface drainage systems for improving water management. Keywords: Corrugated perforated pipes, Exit resistance, Head loss, Subirrigation, Unsaturated zone, Water table response.
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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 | 0.000 | 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) | 0.001 | 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".