Environmental Engineering Reference
In-Depth Information
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Irrigators and civilization battle floods and huge silt load in rivers and
canals until the thirteenth century.
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Mongolian invasions, the Black Death, and Tamerlane put an end to the
maintenance of irrigation and drainage works in the Middle Ages.
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The twentieth century has some rehabilitation of infrastructure:
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1950s: beginning of large impoundments, flood reduction, and drainage
construction to address declining water quality.
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1960s: Gradual decline in water quality (i.e., increased salinity) due to
reception of concentrated return flows from upstream urban, industrial,
and agricultural water users.
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1970s: shift from irrigation and drainage to overdrainage to “reclaim”
(i.e., dry out) the marshes.
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1980s: marshes are embroiled in the Iran-Iraq war.
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1990s: radical acceleration of overdrainage and associated oppression.
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2000s: regime change, unrest, and movement to restore marshes.
The end result has been less water of poorer quality due to increasing salinity, less silt
and organic matter, a shift from irrigation and drainage to overdrainage facilities, and
a reduced indigenous population and knowledge base (Dickey and Madison 2004).
When one examines a salinity map of Iraq, it is possible to trace the water and salt
coming down from the mountains and tending to concentrate in the lower watershed
(this happens in any watershed) with drainage management affecting the regional
distribution of the salt.
There are salt risks present if no marsh restoration occurs:
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Loss of marsh cultural, ecosystem, and economic values
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Loss of critical time, knowledge, and ecosystem resiliency
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Loss of outflow water quality polishing with consequent potential impacts
on the marshes and the Gulf
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Increased dust emissions from desiccated land surfaces
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Increased vulnerability to future flooding
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Acceleration of seawater intrusion due to lack of recharge to the delta
And there are salt considerations to be aware of during the restoration process:
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Avoid ecotoxicity by restricting exposure to highly concentrated waters
that contain specific elements like selenium that are associated with the
salt ions.
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Gather and use indigenous knowledge of salt management in terms of salt-
tolerant plant communities, land variability, and flow regimes, and subsis-
tence agriculture based on historical wisdom.
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Identify and protect critical salt management infrastructure.
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Change operation or configuration of overdrainage facilities to keep water
present or to help return it to the marshes.
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Avoid new salt loads such as those from flood storage in saline sinks prior
to discharge into the marshes.
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