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back to my conributions to the British Permaculture Designers' Teachers' Handbook
(nb. water management in Britain)
Why I would include this subject.
Water management is fundamental to the development of sustainable systems at all scales (garden to planet). Water, soils and bio-diversity (in that order) mark the three essential criteria for the assessment of sustainability in any ecological system.
This can be taught early in a course and provides a general introduction. It could be followed by more detailed work such as reed beds, aquacultures, waste water recycling etc.
Guide to session duration.
Approximately 30 minutes.
How I teach this topic.
White/black board. Main points generated or drawn from group. Leader collates information (or supervises as a group member collates).
Water as essential to life and life processes
Holistic approach vital. Failure of existing water management strategies due to fragmented approach (e.g. farmers, town planners, river authorities, water companies)
Main water storage takes place in the soil, not dams, reservoirs etc. (11% as opposed to less than 0.5%)
Generally within a few hours of the cessation of rain, run-off ceases and dams, reservoirs, rivers and streams are fed by water from soil storage.
At present, emphasis is placed on dams and reservoirs as main water storages fed by run-off. Ditching and drainage often undertaken above such storages in order to increase run off. Agricultural practices (land, marsh drainage) similarly increase run off. Town planning similarly increases run off (roofs, roads and other hard surfaces). All the above encourage removal of water from the system as rapidly as possible- at best into dams and reservoirs, at worst (more likely) into rivers and thus the sea (ie the water is rapidly lost from land based systems).
Run off increases erosion; as speed of flow increases so too does the amount of debris which can be carried (and therefore amount of materials lost from the land based system).
Similar inappropriate practices have reduced the opportunity for water absorption by soils (eg. deforestation, soil impaction by animals and machines, hard surfaces such as roads, buildings etc.).
Therefore as designers we should observe and act on natural processes which have evolved to ensure minimum run-off and maximum absorption in soils.
Reducing run-off and increasing absorption can be achieved by:
(It should be noted that these are also anti-erosion strategies)
As designers we should be concerned with increasing overall yield by ensuring that any plantings associated with water management contain economically viable species (e.g. fuel, fodder, food or cash crops etc.).
In towns and cities where water absorption into soils may be neither appropriate nor possible, increased attention needs to be given to the trapping of water from roof and road surfaces, cleaning and recycling, and/or "downstream" absorption and/or storage (in soils if possible, otherwise in dams and reservoirs).
Link to ethics and principles.
Earthcare: Effective, sustainable management of water resources is essential to existing ecologies.
Peoplecare: Adequate supplies of clean water are essential to human settlements.
Design exercises/group activities.
Useful organisations and booklist.