Environmental Engineering Reference
In-Depth Information
food chain. It then identified low-cost strategies to reduce the risk, which tests
by farmers and consumers showed to work. The project's success influenced
policy in Ghana to allow the use of urban wastewater (PN38) (Abaidoo et al.,
2009; CPWF, 2012).
Excess
Excess water fits our definition of “not being the right amount”. It can vary
from the brief aftermath of a rainstorm, which may damage crops sensitive to
waterlogging, to massive flooding. Floods can result in:
•
ruinous damage to farms and cities;
•
improved income opportunities through wet- or dry-season agriculture,
capture fishing or aquaculture; or
•
both simultaneously, although costs and benefits may accrue to different
groups.
A recent example of a flood disaster is that of the Chao Phrya Basin, central
Thailand in 2011, caused by a combination of bad decisions on reservoir man-
agement, copious late-season precipitation, and the inadequacy of the Bangkok
flood-control system (Komori et al., 2012). There is danger of similar, costly,
man-made floods along a cascade of dams in the Mekong Basin if the dams
are full, late-season rainfall is high, and the dam operators do not communicate
and coordinate water release from the dams (MK3) (Ward et al., 2012).
We found in the Ganges Basin Focal Project that,
Floods are a common feature . . . Flooding in rivers is mainly caused by
inadequate capacity within the banks of the rivers to contain higher flows
[that may be generated by exceptional rainfall or exceptional runoff
resulting from land-use imposed changes in soil structure and thus water
infiltration], riverbanks erosion and silting of riverbeds, landslides leading
to obstruction of flow and change in the river course, poor natural
drainage due to flat floodplains and occurrence of coastal cyclones, and
intense rainfall events . . . Among the South Asian countries, India is more
vulnerable to flood events, followed by Bangladesh.
(PN60) (Mishra, 1997; Sharma, 2010)
The Limpopo Basin suffers severe floods, interspersed with droughts. Although
the basin is on average water scarce, there are peak-rainfall periods during
which large amounts of runoff flow from the basin quickly as floods. The flood
flows are not captured and are not available to agriculture (PN62) (Sullivan
and Sibanda, 2012).
Not all floods are harmful. Smallholder communities use seasonally flooded
lands in Bangladesh for aquaculture to generate substantial income (PN35)
(Sheriff, 2010). The wet-season flood and dry-season ebb of the Mekong
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