1 - What is waterlogging? (This is probably the most frequently asked question}
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In agriculture, waterlogging means that the soil is considered too wet to cultivate crops profitably
(except lowland rice). Waterlogging can be stagnation of water on top of the soil surface and/or the presence of a high water table inside the soil (at a depth of say 0.7 m on average). Surface waterlogging can be seen as a flood control problem or a surface drainage problem. Subsurface waterlogging can be tackled by a subsurface drainage system. As an alternative one may opt for another kind of land use. More information can be found in an article on Drainage Criteria and in a paper on world wide cases of Drainage Systems. See also Wikipedia (watertable control) or WaterWiki (land drainage)
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2 - What kind of drainage systems are applicable under what conditions?
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It is difficult to give a generally valid answer to this question, but the
paper on surface and subsurface drainage systems
gives a summary of practical experiences with different methods under varying
agro-climatologic conditions.
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3 - How can I calculate drainage discharge needs and irrigation/leaching requirements for salinity control using water and salt balances without resorting to simulation models like SaltMod and SahysMod?
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The answers, including the water balance of interceptor (interception) drainage, may be found in
a lecture note on Drainage for Agriculture
presenting Drainage and Hydrology/Salinity, Water and Salt balances. |
4 - What is the influence of land slope on the spacing of subsurface drains?
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The answer is: for drain spacing calculations the slope of the land has little
influence. For this purpose, sloping lands may considered as if they were flat. This is a paper with mathematical explanations
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5 - How can hydraulic conductivity (permeability) of the soil be measured and determined?
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The measurement of hydraulic conductivity can be done in the laboratory or in the
field, above or below the water table, using small scale (auger hole method,
infiltration method) and large scale methods (e.g. using drainage data in existing
experimental fields or in farm land). A full description is given in the chapter "Measurement of hydraulic conductivity of soils". See also the table of contents on line. For well pumping tests to determine aquifer hydraulic properties see the WellDrain model (software page).
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6 - Drain spacing equations for horizontal tile/pipe drains are well known. Can subsurface drainage also be done by (tube)wells and how can the required spacing be calculated?
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The calculation of well spacings for subsurface drainage can be done with
the WellDrain program (see software page). The theory behind it is discussed
in the paper
Well spacing equations. For well pumping tests to determine aquifer hydraulic properties see the WellDrain model (software page).
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7 - What is the optimimum depth of the water table and how can we develop suitable drainage criteria to design a subsurface drainage system
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This is the lecture note on
Agricultural Drainage criteria. The table of contents can be seen on line.
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8 - What envelope materials (filters, wraps) are used for pipe drains?
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This is a pdf file made of scannned pages
on the subject taken from an ILRI publication.
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9 - How is the river and surface water pollution tackled in The Netherlands?
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I am not a lawyer nor a specialist on pollution with organic compounds. Yet I made
a summary of the Dutch "Law Pollution Surface Water" to the best of my ability.
This is the summary. Further a powerpoint presentation of the summary ("summary of the summary") can be downloaded or viewed on-line. |
