Understanding the WatershedUnderstanding where you are in the watershed is an important step in site analysis. This video discusses how water moves in the large scale landscape and how location within a watershed affects a site. Oregon State University Free Permaculture Course (http://open.oregonstate.edu/courses/p...)
A Water ManifestoBelow is an extract from the Manifesto of the Permaculture People’s Party, April 2008, which is a good summary for a sane water policy.
Swales
If we allow 100% for the water that fall on an area of land, probably 80% of this precipitation is as a result of condensation of moist air on leaves. Some countries measure both rainfall and condensation (South Africa and Tasmania).
If we allow 100% for precipitation, 88% of it runs off the land and goes into the sea or to inland depressions or evaporates, leaving only 12% for all the duties of water. This is the major waste of water.
If you survey dead level lines across the landscape at intervals not exceeding 100m and commencing at 2m below the top of the slope, then all the water that runs across the surface of the land will pool in channels dug along these lines, ranging from .5 to 3m width and .5 to 1.5 m deep, called swales. The spoil from this channel is piled on the lower lip of the swale.
If rain persists above 12mm in one hour, water flows across the lands and pools in the swales. No water leaves the property. Usually within 3 hours, all this water soaks in and is immune from evaporation or run off loss. That is the swale system affords a total water conservation of precipitation. No other system does this.
What is the ultimate use of this water? Modern swales in California within the settlement of Village Homes stored in their first year about 2m of saturated soil below the swale base. That is now some 18m deep, and we can expect all swales in effect to store vast quantities of water adjacent to the swale. After a few years, trees planted below the line of the swale are drought immune and add their share of condensation moisture to precipitation.
A landscape of swales and trees is in effect drought proof and eternally productive. Thus we believe that all such earthworks should be not only tax deductible but encouraged by all authorities in order to restore landscapes to health.
We have inspected 60 year old swales that Franklin Delano Roosevelt had people build through deserts, dug by FDR’s corps of workers in the 1930’s. They have never ceased to stabilise the dry lands evaporation and erosion and grow large trees.
A proportion of all state money should always go towards the construction of swales in cities and all farms. This we see as a national priority to off set desertification and global warming.
Swales need to be part of every subdivision plan and are easily placed in open forests because it is possible to dig above and below the survey line and thus around trees. The only places where swales are not recommended by us are the steep slump slopes of deforested basalt flows. These are liable to slump with high water content in the soil.
It is safe for wheeled tractors to create swales up to 12% slope. Above this they must be hand dug or made by crawler excavators.
We believe it is possible to restore the entire Murray – Darling system with a national swaling program for the system. This would be a permanent solution for river flow but would never cope with lavish irrigation of unsuitable crops such as rice and cotton.
In Tucson, Arizona, those gardens we have swaled from the downpipe are noticeably green while others are desert gardens.
Rainwater
Rainwater from roofs should be stored in large tanks for every house and impeding bylaws that prevent this should be nullified. Every building can supply its own water needs. Some commercial buildings can supply water for many homes.
We support a 100% government subsidy for the purchase, construction, fittings and associated plumbing services for rainwater tanks.
Wycheproof collects the water from all housing roofing and pumps it out to holding lagoons for public use. Ideally such lagoons should be roofed to prevent evaporation or covered with floating white blocks to reflect the sun, as in South Africa.
Civil Engineering
All civil engineers must be instructed on uses of swales to accept road run-off on both sides of the road to grow rows of trees as seen in Mexico, and NEVER to concentrate run-off in concrete pipes and shoot it down hill from the road. In this way they have created gullies by our roads. They must be directed to go back and swale all of our water. Every desert gulch has been created by civil engineers. Australia can not afford any such incidents. The civil engineer of Pt Augusta, South Australia, created swales and so this town looks like a forest when approached. |
“Water, energy and food are freely available for the whole of humankind!”
Dieter Duhm, from the Tamera Manifesto for a New Generation on Planet Earth.
