Diverse irrigated areas were mapped in the Krishna River Basin (258,912 km 2 ), southern India, using an irrigated fraction approach and multiple ancillary data sources. Unsupervised classification of a monthly time series of net difference vegetation index (NDVI) images from the Moderate Resolution Imaging Spectrometer (MODIS) over January–December 2002 generated 40 classes. Nine generalized classes included five irrigated classes with distinct NDVI time signatures: continuous irrigation, double‐cropped, irrigated with low biomass, minor irrigation, and groundwater irrigation. Areas irrigated by surface water began greening 45 days after groundwater‐irrigated areas, which allowed separation of surface and groundwater irrigation in the classification. The fraction of each class area irrigated was determined using three different methods: ground truth data, a linear regression model calibrated to agricultural census data, and visual interpretation of Landsat TM imagery. Irrigated fractions determined by the three methods varied least for the double‐cropped irrigated class (0.62–0.79) and rangeland (0.00–0.02), and most for the minor irrigated class (0.06–0.43). Small irrigated patches (
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Document Type: Research Article
Department of Geography and Regional Development, University of Arizona, Tucson, AZ 85721
International Water Management Institute, Headquarters, Colombo, Sri Lanka
International Water Management Institute, South Asia Regional Office, Patancheru, Andhra Pradesh, India, 502‐324
Publication date: 2006-10-10
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