Paddy Field Characteristics in Water Use: Experience in Asia - Water and Agriculture: Sustainability, Markets and Policies - page 210

1.5 billion ha. However, irrigable land in Asia occupies some 66% of the world's
irrigable land area of about 270 million ha. The majority of this irrigable land is in paddy
fields that extend over the whole of the Asian monsoon region. It goes without saying that
the majority of Asia's massive population is supported by intensive paddy rice cultivation
which offers high land productivity, based on irrigation.
Paddy rice cultivation in the Asian monsoon region is not only an excellent form of
agriculture offering high land productivity and stable yields, but it could also be seen as a
sustainable and environmentally friendly economic activity that suits the climatic and
topographical conditions of this warm, humid region. This form of agriculture, an
economic activity, has continued to evolve for hundreds to thousands of years at many
sites, as witnessed by archaeological traces of 7000-year-old rice cultivation in China.
And still today, it forms a unique natural feature and cultural climate by the endeavour of
people living in symbiosis with water.
This unique natural feature and cultural climate, a complex amalgamation of this
sustainable human activity, society and the natural environment, ranks alongside rice
itself as another product of paddy rice farming. Water in paddy fields and irrigation-and-
drainage system serves as a network of wetlands and waterways, and creates an excellent
secondary natural environment with an enriched flora and fauna. Furthermore, it also
supports the convenience of life for city dwellers through recharging groundwater,
reducing peak flood flows, supporting biodiversity and so on. These functions are non-
commoditised “products” provided jointly and consumed publicly.
When a given economic activity brings profit to other economic entities through non-
market means, we say that it performs positive economic externality, or it has an external
economy. We shall call above-mentioned functions “the multi-functional roles of paddy
field irrigation” as positive economic externalities. In the Asian monsoon region, as
elsewhere, the rapid modernisation of socio-economic activity and the rapid growth of
cities and industries have inevitably impacted on the rural socio-economy. In many places
in arid and semi-arid regions, as the socio-economy grows, improper agricultural water
use has caused problems such as accumulation of soil salinity, depletion of groundwater
resources and degradation of biodiversity. What impacts will the rapid modernisation of
Asian-style small-scale, labour-intensive paddy rice cultivation bring to the natural
environment created by rural society and paddy rice farming, and the multi-functional
roles of paddy field irrigation enjoyed by city dwellers?
In responding to these questions, we shall illustrate the multi-functional roles of
paddy field irrigation in humid regions by comparing their hydrological environment,
forms of irrigation and characteristics of paddy fields with those in arid and semi-arid
regions. We shall go on to examine methods of quantitatively or economically evaluating
these multi-functional roles, and make policy proposals for Asian monsoon countries and
the rest of the world on the problems awaiting solution.
2. Characteristics and roles of paddy rice farming in the Asian Monsoon Region
2.1 Natural conditions
The Asian monsoon region embraces the Indian Ocean to the south, the expansive
region of Tibet, the Himalayan mountain mass and continental China to the north, and the
Pacific Ocean to the east. Most of it consists of high-precipitation warm regions that have