IWRA World Water Congress 2008 Montpellier France
2. Towards the Future: Water Resources and Global Changes
of the corresponding author
Dr. Madhusudan Bhattarai
P. O. Box 42, Shanhua,
Tainan, Taiwan 74199, ROC
Phone: (+886-6) 583-7801
Fax : (+886-6) 583- 0009
Environmental Kuznets Curve for
Irrigation, Irrigation Demand, Population Growth, Economic Development, Global Irrigation Modelling, Asia, Africa,
Latin America, Cross-countries Analysis
This paper verifies an existence of the
Environmental Kuznets Curve (EKC) hypothesis for irrigation. The EKC hypothesis suggests for an inverse U-
shaped (or concave) relationship between the level of environmental degradation and income in a given society. It
also implies that some form of environmental deterioration appears inevitable during the initial stage of development,
but subsequent increases in the social income would generate enough incentives to improve the environmental quality.
In line with this reasoning, the EKC relationship for irrigation (referred to here as Irrigation Kuznets Curve, or IKC)
is hypothesized suggesting that the demand for irrigation is greater at the initial stage of development and that
irrigation demand declines as social income increases. This process subsequently gives rise to an inverted U-shaped
relationship between the level of irrigation and the level of income. This information on EKC for irrigation has large
implications on policy planning for irrigation and for analyzing demand for irrigation, and water uses and water
reallocations across sectors.
The major objective of this study is to empirically verify the
presence of the EKC relationship for irrigation and to illustrate its policy implications. Subsequently, it also evaluates:
i) the impact of selected macroeconomic policy, structural and governance related factors (population,
energy use, technological change) affecting the irrigation-income relationship across the countries;
policy implications of the empirical findings on EKC for future demand for irrigation and demand for water
resources, in general.
In this study, the EKC hypothesis for irrigation (i.e., IKC) is examined
across 66 tropical countries from Asia, Africa and Latin America using national-level annual data from 1972 to
1991. The IKC model is once estimated for 66 tropical countries, and separately for 13 countries from Asia where
more than two-thirds of the global irrigated land is located. Two measures of irrigation are used, “percentage of crop
area irrigated” and “relative change in net irrigated area.” In addition to estimating irrigation and income relationship,
effects of other broad-level institutions and policy factors on irrigation are also analyzed such as governance (sum
total of political and civil liberty indices), cereal yield, agricultural value added, manufacturing value added growth,
rural population density, economic growth rate, and per capita electricity use.
Results, Conclusions, and
The empirical results provide strong evidence for the existence of an EKC relationship for
the two measures of irrigation used, and for both the tropical-global and the Asia EKC models. This means that the
pace of irrigation development is faster at the initial stage of a country’s development and that it will be at a slower
rate at the later stage of development. The empirical findings also imply that there is no leapfrogging in the process of
irrigation and agricultural development and management of natural resources in an economy.
relationship (elasticity value) estimated between irrigation and a nation’s income has profound impacts for better
forecasting irrigated-area (and water demand) in an economy, as opposed to the zero-income elasticity of irrigation
assumed in most past studies. Irrigation area and water-demand analyses are so far mostly based upon per capita
requirement type of forecast-modeling technique, which ignores the underlying income effects and societal
substitutional behavior over resources use decisions as shown in IKC modeling here. The study findings contribute
significantly in global debates on water and assessment on future water needs.