Vegetation growth zonation of Sri Lanka for improved water resources planning

Water resources planning depends on the physical environments, notably on the vegetation and hydrological conditions in river basins. Vegetation growth—both natural and human induced—has a strong dynamic behavior which, especially at larger scales, is difficult to survey in the field. Low cost imagery from the NOAA–AVHRR satellite provides new opportunities to estimate vegetation development and biomass production. Composite maps of biomass production were compiled as the primary basis to establish a growth zone classification. A total of 92 vegetation growth zones were delineated by visual interpretation. Digital vector maps of land use and soil type, as well as digital raster maps of moisture availability index, soil moisture and actual evapotranspiration have been explored to describe vegetation growth zones from satellite data. These vegetation growth zones will contribute more to water resources planning than existing agro-ecological zonations and land use mapping, because vegetation growth is based on the environment and has strong linkages with the hydrological processes occurring in different parts of the basin. It provides a vehicle to relate water demand and water use in river basins to various types of vegetation.