SEASONAL GROUND COVER MONITORING WITH LANDSAT TIME SERIES DATA IN THE GRAZING LANDS OF THE GREAT BARRIER REEF CATCHMENTS Michael Schmidt and Rebecca Trevithick Department of Environment and Resource Management Climate Building 80 Meiers Rd Indooroopilly QLD 4068 Phone: 07 3896 9297 Facsimile 07 3896 9843 michael.schmidt@nrw.qld.gov.au Abstract Ground cover is a critical attribute of the landscape affecting infiltration and can functionally be related to surface runoff, nutrient fluxes and soil erosion. Ground cover relates to living and non-living materials on the soil surface. Besides the direct economic value for graziers, varying levels of ground cover have indirect economic and major ecological implications on productivity, land condition and biodiversity. Remote sensing offers one of the few ways to monitor long term ground cover change over large spatial extents. This work is supporting the recently initiated Great Barrier Reef Water Quality Protection Plan to limit negative environmental impacts to the Great Barrier Reef. Landsat Thematic Mapper and Enhanced Thematic Mapper+ imagery have recently become freely available and thus make possible time series applications on medium-high spatial resolution data at a temporal resolution greater than annual. This contribution outlines the operational product development of a seasonal ground cover product based on different temporal compositing methods. Introduction Queensland's rangelands are subject to high climate variability on seasonal, annual, decadal and longer timescales, making management for economic and environmental sustainability difficult. Ground cover levels may vary due to anthropogenic management of grazing enterprises and agricultural land management practices, or natural seasonal changes in rainfall. Dynamic ground cover information is important for reliably estimating soil erosion and nutrient flux into the stream network and the adjacent Great Barrier Reef (GBR). With the United States Geologic Survey (USGS) opening their Landsat image archive freely to the public, all archived images from 1999 onwards are now available with next to no budget constraints. This coverage of up to 20 images per year creates new opportunities for Landsat based time series analysis and environmental monitoring approaches. To date, the ground cover monitoring program within the Department of Environment and Resource management (DERM) has reported annually on 1