[Terrapreta] Dams & wetter air (Off topic, or not off topic. That is the question.)

[Michael Bailes]

I am sorry I can't find the total square miles kilometres of extra water
that dams present to evaporation.

However here are a few articles that will give you a bit of the flavour of
what has been happening in the last 50-100 years.but here is the evaporation
in a small corner of Queensland for example

 Water authorities in south-east Queensland have calculated
evaporationlosses are equal to the annual consumption of
> 1.6 million households.

<http://forums.hypography.com/chemistry/6506-salt-nacl-sodium-chloride.html?highlight=salt>
http://forums.hypography.com/search.php?searchid=204157


About 1,200 dams higher than 15 metres are started worldwide every year.
>
 Current major river engineering projects planned or under construction
> include:
>
> - A programme to build a staircase of six major hydroelectric dams on the
> Mekong, a river whose biodiversity is considered second only to the Amazon
> and whose fishery and floodplains support much of the population of
> Cambodia.
>
> - A plan to build a 3,400 kilometres shipping channel, the Hidrovia, up
> the Paraguay and Parana Rivers into the 200,000 square kilometres Pantanal,
> one of the world's largest tropical wetlands.
>
> - The construction of the Three Gorges Dam, the world's largest hydro
> project, across the Yangtze River, displacing more than 1.2 million people
> and irrevocably changing the river system.
>
>
http://www.unep.org/ourplanet/imgversn/83/williams.html

* *

*

1.4.6. Water power – Dammed or damned?
*

The power of water can be harnessed to supply the energy needed for
development without recourse to other more polluting forms of generation.
Hydro-power brings benefits, but it also causes great environmental damage
including lowering of river flows downstream, disruption to natural patterns
of soil fertility, displacement of peoples, increased health risks,
destruction of habitat both upstream and downstream, and the potential for
major conflict over international property rights. Thus, the negative
environmental effects may far outweigh any social or economic benefits.
Nevertheless there are in place or planned over 38,000 large dams in the
world and countless smaller ones – over half of these large dams are in
China, including the recently-begun Three Gorges complex on the Yangtse.

   - The Aswan Dam supplies half of Egypt's total energy needs and has
   brought freedom from seasonal flooding; but at a cost . . .

  100 million tonnes of silt, clay and sand are now filling Lake Nasser.
This silt would formerly have fertilised fields in the floodplain, so vast
amounts of fertiliser are imported to counter the loss;

Offshore sardine fisheries have been hit hard – there has been a drop of 83%
in annual harvest in the eastern Mediterranean caused by lack of nutrients
and effects of low flows, etc. on breeding grounds; of the 47 species of
fish formerly harvested, only 17 were harvestable a decade after completion
of the dam.

The Nile Delta is in retreat and soil salinity and waterlogging has
increased (the FAO reckon that 35% of Egypt's cultivated land is affected by
salinisation and 90% by waterlogging); recent research indicates that Egypt
could lose 19% of its habitable land within 60 years, displacing 16% of its
population.

The incidence of schistosomiasis has exploded among people living around
Lake Nasser.

 Laos is to build 23 dams by the year 2010 in order to supply cheap
electricity to the tiger economy of Thailand; such a major taming of the
Mekong and its tributaries could have a serious effect upon flows in both
Laos and Vietnam.
The great flooded forest region of the Amazon is threatened by low flows
caused by upriver damming projects and direct habitat destruction. It is
estimated that in the lower Amazon only 15-20% of previously flooded forest
remains. The 6,500 km length of the Amazon contains one-fifth of all the
world's freshwater discharge into the oceans; during half the year portions
up to 20km from the river are flooded to a depth of several metres covering
an area of 150,000 sq km (total of the Amazonian rainforest = 5 million sq
km)
The flow of the Colorado is impeded by 10 major dams. Unless there is
extremely high rainfall, the river does not reach the Sea of Cortez; as a
result the fisheries in the sea have collapsed and coastal communities
devastated.
21 million people in India have been dislocated as a result of dam projects
in the last 40 years.



http://www.ramsar.org/wwd/0/wwd_bureau_hulyer.htm

IN 100 YEARS
> growth in human population which has increased from approximately 1.6billion to over 6 billion.
>
A lot of sweaty humans?

The International Rivers Institute not happy about dams
http://www.irn.org/basics/ard/index.php?id=damqa.html

This is getting abit more to the point

> Today, there are more than 45,000 large dams (dams more than 15 meters
> high) in the world—most of them built in the last 35 years (WCD 2000:8,
> 11). This storage capacity represents a 700 percent increase in the standing
> stock of water in river systems since 1950 (Vörösmarty et al. 1997:210).
>
> The increase in storage capacity has permitted the expansion of
> agriculture through the use of irrigation, as well as the capability to
> distribute water more evenly throughout the year in many areas of the world
> where seasonal water shortages are a problem.


But water demand is growing quickly, jeopardizing the availability of the
> supplies we would like to collect, store and use. Global water consumption
> rose sixfold between 1900 and 1995—more than double the rate of population
> growth—and continues to grow rapidly as agricultural, industrial, and
> domestic demand increases (WMO 1997:9).



>From the Nile to China's Yellow River, some of the world's great water
> systems are now under such pressure that they often fail to deposit their
> water in the ocean or are interrupted in the course to the sea, with grave
> consequences for the planet.
>
>     Adding to the disaster, all of the 20 longer rivers are being
> disrupted by big dams. One-fifth of all freshwater fish species either face
> extinction or are already extinct.
>
 http://www.truthout.org/cgi-bin/artman/exec/view.cgi/58/18345




>    - *Irrigation problems. * Food supply is threatened not only by
>    water shortages themselves but also by ineffective irrigation practices.
>    Although only 17 per cent of all croplands are under irrigation, these lands
>    produce one third of the world's total food supply.37<http://www.unfpa.org/swp/2001/english/notes.html#2-37>Less than half of all water withdrawn for irrigation purposes actually
>    reaches the crops. The rest soaks into unlined canals, leaks out of pipes or
>    evaporates on its way to the fields.38<http://www.unfpa.org/swp/2001/english/notes.html#2-38>
>
> Badly planned and poorly built irrigation systems have reduced yields on
> one half of all irrigated land, according to a 1995 estimate by FAO.39<http://www.unfpa.org/swp/2001/english/notes.html#2-39>The two main problems are salinization and waterlogging of crops. FAO
> estimates that salt build-up in soil has severely damaged 25-30 million
> hectares of the world's 255 million hectares of irrigated land.40<http://www.unfpa.org/swp/2001/english/notes.html#2-40>Another 80 million hectares are affected by a combination of salinization
> and waterlogging. 41<http://www.unfpa.org/swp/2001/english/notes.html#2-41>
> Every year, on average, about 1.5 million hectares of irrigated land is
> taken out of production because of salt build-up alone, half of the amount
> of land brought into production. --


http://www.unfpa.org/swp/2001/english/ch02.html

http://forums.hypography.com/chemistry/6506-salt-nacl-sodium-chloride.html?highlight=salt





Michael the Archangel

"You can fix all the world's problems in a garden. . . .
Most people don't know that"
FROM
http://www.blog.thesietch.org/wp-content/permaculture.swf
-------------- next part --------------
An HTML attachment was scrubbed...
URL: /pipermail/terrapreta_bioenergylists.org/attachments/20071108/beb3a707/attachment.html