108
Chapter 12
Pan-European Land Cover Monitoring (PELCOM) distinguishes typically
non-irrigated arable land, irrigated arable land, permanent crops (e.g.,
vineyards, orchards), winter crops and complex cultivation practices. These
databases are both essential pieces of information for global terrestrial ecohydrological descriptions, and critical for the description of agro-ecological
zones found within river basins. Multi-temporal and multi-spectral
classifications have also been worked out for the delineation of agro-ecoclimatic zones (e.g., Brown et al., 1993; Menenti et al., 1993; Lambin and
Ehrlich, 1996; Maselli et al., 1996) and are essential for the distribution of
water among for instance irrigated agriculture, wetlands and forests.
Traditional inventories of the world’s irrigated areas are almost
exclusively based on information provided by governments, and the
procedures followed in the data gathering process is inherently nonsystematic. For example, official irrigation statistics often reflect design
areas rather than actually irrigated areas. Although FAO promulgates the
AQUASTAT database, its accuracy, in the absence of independent
estimates, is difficult to assess. The number of irrigation seasons can vary
from once in a few years up to three times per year for paddy crops
cultivated in the humid tropics. Furthermore, irrigated areas expand and
shrink continuously due to market prices, land degradation and unreliability
in the irrigation service.
Until recently, the ability to delineate irrigated areas systematically and
globally did not exist. A test with NOAA satellite data in Argentina using
the Fourier analysis methodology proposed by Azzali and Menenti (1996),
revealed that the satellite interpreted permanently irrigated area was 843,300
ha whereas the FAO statistics gave 1,632,000 ha—hence a 94% difference!
A comparison for the Iberian Peninsula using FAO figures and data from the
CORINE land cover database revealed larger deviations. Hence, our
knowledge on the extent of irrigated areas is poor by inadequate
conventional methods, and the need exists to get more accurate statistics at
the regional scale.
3.
INFORMATION NEEDS FOR THE ANALYSIS OF
IRRIGATED AGRICULTURE
In spite of the rapid growth of the aforementioned databases on global
and regional scale, information to improve the water resources management
in large-scale irrigation systems is seriously inadequate. River basins are
faced with water competition among users and the quantification of water
flowing to the sea, wetlands, flushing, navigation, in-stream recreational
purposes and so on is gaining importance. A well-balanced partitioning of
Chapter 12
Pan-European Land Cover Monitoring (PELCOM) distinguishes typically
non-irrigated arable land, irrigated arable land, permanent crops (e.g.,
vineyards, orchards), winter crops and complex cultivation practices. These
databases are both essential pieces of information for global terrestrial ecohydrological descriptions, and critical for the description of agro-ecological
zones found within river basins. Multi-temporal and multi-spectral
classifications have also been worked out for the delineation of agro-ecoclimatic zones (e.g., Brown et al., 1993; Menenti et al., 1993; Lambin and
Ehrlich, 1996; Maselli et al., 1996) and are essential for the distribution of
water among for instance irrigated agriculture, wetlands and forests.
Traditional inventories of the world’s irrigated areas are almost
exclusively based on information provided by governments, and the
procedures followed in the data gathering process is inherently nonsystematic. For example, official irrigation statistics often reflect design
areas rather than actually irrigated areas. Although FAO promulgates the
AQUASTAT database, its accuracy, in the absence of independent
estimates, is difficult to assess. The number of irrigation seasons can vary
from once in a few years up to three times per year for paddy crops
cultivated in the humid tropics. Furthermore, irrigated areas expand and
shrink continuously due to market prices, land degradation and unreliability
in the irrigation service.
Until recently, the ability to delineate irrigated areas systematically and
globally did not exist. A test with NOAA satellite data in Argentina using
the Fourier analysis methodology proposed by Azzali and Menenti (1996),
revealed that the satellite interpreted permanently irrigated area was 843,300
ha whereas the FAO statistics gave 1,632,000 ha—hence a 94% difference!
A comparison for the Iberian Peninsula using FAO figures and data from the
CORINE land cover database revealed larger deviations. Hence, our
knowledge on the extent of irrigated areas is poor by inadequate
conventional methods, and the need exists to get more accurate statistics at
the regional scale.
3.
INFORMATION NEEDS FOR THE ANALYSIS OF
IRRIGATED AGRICULTURE
In spite of the rapid growth of the aforementioned databases on global
and regional scale, information to improve the water resources management
in large-scale irrigation systems is seriously inadequate. River basins are
faced with water competition among users and the quantification of water
flowing to the sea, wetlands, flushing, navigation, in-stream recreational
purposes and so on is gaining importance. A well-balanced partitioning of