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Greater Poland · teaching diagram A-1

Drains beneath a Greater Poland field

The plan shows intent. Whether the pipe was built and whether it carries water today are separate pieces of evidence. Select a segment and see what is missing.

Front of the sheet: a cultivated field seen from above, with no pipes visible Schematic drawing, not a photograph: a field with crop rows, a ditch on the right and a round marker for outlet Z0 on its edge. The position of the selected segment from the plan is marked with a dashed line. These are coordinates from the plan, not a trace visible in the field.
Reverse of the sheet: schematic plan of drainage network A-1 Teaching diagram, not a map: the horizontal collector Z1 leads through the short outlet Z0 to the ditch on the right. Three laterals S1, S2 and S3 join the collector from above. The line style shows the kind of evidence entered for a segment; the legend is lower down the page.

The front is a drawing, not a photograph: we have no photograph of a field with usage rights. The dashed line on the front is the position of the segment according to the plan, not a trace in the field. The line type on the reverse shows the kind of evidence (legend). Diagram A-1 is a model, not a plan of any plot.

Without JavaScript you see the initial state: all segments are only designed; construction and today’s state have not been checked.

Select a segment (or tap a line on the reverse)

Route from the selected segment to the ditch: three layers of evidence

  • Designdesignedin diagram A-1 (model)
  • Constructionnot checkedsegments with a record: 0/3
  • State todaynot checkedsegments observed: 0/3

You cannot say that Lateral S2 is working: the route S2 → Z1 → Z0 → ditch has not been confirmed as clear. Presence on the plan proves nothing here on its own.

What you need in hand to write “working”

The plan shows intent. A construction record shows that someone laid the pipe, or that no trace of it was found in the files. An observation or test today shows the state on the day of observation. No layer replaces the next. Water flows through a single series: if one link on the route to the ditch is broken or unexamined, a conclusion about the whole pipeline is unwarranted. Below you enter what evidence you would have in hand. This is an exercise on model A-1, not a register of a real network.

Example evidence combinations (model)

Links on the route to the ditch

Conclusion for the selected route

You cannot say that Lateral S2 is working: the route S2 → Z1 → Z0 → ditch has not been confirmed as clear. Presence on the plan proves nothing here on its own.

Still to check whether a construction record exists: S2, Z1, Z0.

Missing an observation or test of today’s state: S2, Z1, Z0.

“Not found” means only that the source search returned no result. It is not proof that there is no pipe. “Clear” refers to the day of observation.

State of all segments

  • Lateral S1: construction: not checked; today: not checked.
  • Lateral S2 (selected): construction: not checked; today: not checked.
  • Lateral S3: construction: not checked; today: not checked.
  • Collector Z1: construction: not checked; today: not checked.
  • Outlet Z0: construction: not checked; today: not checked.

Legend of lines on the reverse

  • dashed: designed only
  • solid graphite: construction record exists
  • dotted: not found in the files
  • blue: observation today, clear
  • red with a cross: observation today, broken
  • yellow glow: selected segment and route to the ditch

On the front of the sheet the round marker by the ditch shows the state of outlet Z0 alone: “?” not checked, “✓” clear, “×” broken.

Why continuity to the ditch matters: the same downpour, two ends of a range

The strip of soil above segment Lateral S2 receives rain. The retained pool (notional 40 mm) stays in the micropores and the drain does not take it. The free pool (notional 20 mm) can be removed up to the limit, but only if the route to the ditch is clear. Both columns count the same rain. Which of them may be taken as the result depends on the evidence from part 2; where it is missing, the result is a range. Start: 30 + 12 mm; the capacities and the limit are teaching parameters, not measurements from Greater Poland.

Result unknown. After 3 steps the drain will carry away between 0 and 24 mm, and the excess leaving the strip will be between 10 and 34 mm.

First tops up the retained pool (up to 40 mm); the rest feeds the free pool.

Removes water only from the retained pool.

How much the drain can remove from the free pool when the route to the ditch is clear (model assumption).

The step is repeated this many times with the values above.

Without JavaScript the sliders are unavailable and the figures beside them show the default values: rainfall 20 mm per step, evapotranspiration 4 mm, drain limit 8 mm, 3 steps.

A · clear route

Upper bound of the range. It is not known whether this is the case.

retained
36 mm
free
20 mm
removed by drain
24 mm
excess outside the strip
10 mm

42 + 60 − 12 − 24 − 10 = 56 mm

B · broken route

Lower bound of the range. It is not known whether this is the case.

retained
36 mm
free
20 mm
removed by drain
0 mm
excess outside the strip
34 mm

42 + 60 − 12 − 0 − 34 = 56 mm

Equation: start 42 mm + rainfall − evapotranspiration − drain − excess = end. The sum balances in both columns.

The 8 mm limit per step is a model assumption (column A). Column B is the same rain with a break in the network: 0 mm. An unverified segment is a range between them, not a value in the middle.

Files are not a map of working pipes

Limits of this page

  • Diagram A-1 is a teaching device: the layout of segments, the 40 and 20 mm capacities, the 30 + 12 mm start, the limit and the rainfall are notional. They do not describe any plot in Greater Poland.
  • The drawing is not a map or an overlay on an orthophoto map. We have no scan of an estate plan and no photograph of a field with usage rights, so the front of the sheet is a drawing.
  • The existence of a design does not prove construction, and documented construction does not prove that the pipe is clear today. The evidence entered is an exercise; the page does not know the state of any real network.
  • The balance of two pools shows a relationship; it is not a hydrological model. The page does not assess how a system works on a particular plot and does not advise on rebuilding. Entering someone else’s land and working on a ditch require the consent of the owner or manager.
  • To be verified: the source descriptions below were carried over from an earlier version and were not reopened when this page was built.

What was removed from version V2 and why

  • Three view tabs: the plan and the surface are now always together on one sheet. The soil cross-section was replaced by the balance bar.
  • Moisture zones on the surface: removed, because the diagram does not predict where water will stand.
  • Segments S4 and S5, contour lines, a 3‰ gradient: decoration with no description and no effect on the result.
  • The “link limit to network” switch and the independent mode: replaced by two columns side by side. A 0 mm limit set with the slider is still distinguished from a network failure.
  • Field notebook in browser storage: removed. The page saves nothing.
  • Remote photograph from Auckland Museum: not embedded (the page works offline); only the link remains.

Kept: the chain of continuity to the ditch, the unverified state as a range instead of a single number, the two 40/20 mm pools in the same order within a step, conservation of the total, the sources.

Sources