v) Growing drought tolerant crops such as cassava, sorghum... on well m
ulched raised beds or ridges. The furrows serve as water reservoir t
rap-ping fresh water from the flooding season.
vi) Building flood protecting polders for growing fruit trees or hlgh qu
ality crops in flood-prone areas, particularly the Mekong Delta.
4.2.3 Restricted use of underground water. It is economical to develop sh
al-low aqulfers for small scale irrigation by an individual or a sm
all group of farmers, Among the advantages of this technology are t
he renewable storage of the aquifer by annual flooding or rainfall,
the minimal loss in conveyance, and the low cost of construction.
4.3 Expansion of new irrigated areas.
International investments for new dams, reservoirs, and irrigation scheme
s have been on the decline substantially due to high cost, Iow efficienci
es, and envi-ronmcntal hazards. However, the huge corporate profits of th
ese large engi-neering projects often overruled environmental and social
benefits. Therefore despite all crltics, such mammoth projects as the Thr
ee Gorges Project in China, the Son la Project in northern Vietnam, the N
am Ngeun 11 Project in Laos... will go ahead. As indlcated above, when ne
w irrigation schemes are necessary, careful selection of dam sites where
only least environmental and social impacts will have to be allowed.
4.4 Desalination
We can have as much fresh water as we want from desalination of seawater,
but at extremely high cost (USD 1-2 per m3) wlth the present technology
that only the oll-rich countries in the Persian Gulf can afford. This wat
er can be used to grow hlgh quality vegetables by hydroponic method under
the glasshouse, but hard]y for food crops.
4.5 Improving water allocation policies
Experiences with irrigation systems In Asla showed that much of the ineff
lcien-cies in the use of expensive water for agriculture can be attribute
d to inappro-priate allocation policies. The painful result is big losses
and wasteful use. Future demand for irrigation can come from savings fro
m current uses. Mark Rosegrant, and expert in water management policy of
the International Pood Policy Research Institute, concurred that such a r
eform will not be easy, because both long-standing practice and cultural
and religious beliefs have treated water as a free good, and because entr
enched interests benefit from the existlng sys-tem of subsidies and admin
istered allocations of water. However, there may be four types of alterna
tive water mechanisms to consider in setting appropriate
