Mapping and monitoring lakes in the Brazilian Pantanal wetland using synthetic aperture radar imagery

1. The Pantanal wetland in South America is being threatened by human development, such as the construction of hydropower dams in the upper Paraguay River and the Hydrovia. The consequences of these developments are difficult to predict, but will potentially cause irreversible loss of habitat and biodiversity. 2. Radar satellite imagery can be used to establish baseline information that is crucial for monitoring changes in this region. In the case of the Pantanal, the pixel spacing of the imagery is a major concern if the goal is to count, map, and monitor lakes. To address this, Radarsat and JERS-1 data were acquired and used to produce a series of coarser-resolution images in order to understand the capabilities of the various resolutions to map Pantanal lake ecosystems. The simulations included resolutions of the existing JERS-1 mosaics (100m resolution) and the proposed ALOS/PALSAR mosaics (50m resolution). 3. Using the 15 in data it was found that in the Nhecolandia region of the Pantanal, only about 7% of lakes have an area larger than 0.2 km(2), 47% have an area larger than 0.05 km(2), and 50% are smaller than 0.05 km(2). Therefore, it is important to consider the substantial number of lakes smaller than 0.05 km(2). 4. The size of the errors in determining lake area depends on lake size, lake shape, and the image pixel spacing - long and small lakes have greater errors, and 100m resolution images show unacceptable errors. The error in estimating lake area associated with the pixel spacing of the Radarsat ScanSAR image is 12.5% and 25%, and for the proposed mosaics of ALOS/PALSAR it is 30% and 47% for lakes larger and smaller than 0.05 km 2 respectively. Therefore, based on simulated results, the spatial resolution of the observing SAR was an important determining factor in the capacity to discriminate small lakes in the Pantanal. Copyright (c) 2007 John Wiley & Sons, Ltd.