Application of Radar Altimetry in Detecting the Changes of Wetlands and Lakes in the Prairie Pothole Region
Franklin W Schwartz(1) , Bo Zhang(1) , C.K. SHUM(1) , C.K. SHUM(1) , and Yuchan YI(1)
The Ohio State Univ,
125 S. Oval Mall, Mendenhall Lab 275,
Columbus, OH 43210,
The influence of climate change and climate variability in the Prairie Pothole region (PPR) of North America has emerged as a problem of particular concern in recent years, given two scale of the region, satellite remote sensing has emerged as a critical technology for the investigation of hydrology, ecology, geology and climatology. The severe drought in 1988-92 led to tremendous shrinkage of the lakes and wetlands. This extreme was followed by the most significant wet period of the century in the middle to late 1990s. Although imagery satellite sensors have been widely applied in hydrological studies, the large-scale space/time syntheses were prohibited by cloud coverage and limited availability of the repeatable scenes. Fortunately, Radar altimetry, e.g., NASA/CNES TOPEX/POSEIDON (T/P) mission, with relatively short measurement cycles (weeks), a diminished atmospheric influence (at Ku-band radar frequency) and a longer than 10 years observational span (1992 to present), provides an excellent tool to assess hydrological changes, e.g., the extents and their changes of potholes, in the PPR. New techniques are developed using backscatter data from radar waveforms to develop a practical classification approach to examine how the numbers and general size of pothole lakes and wetlands change, representing the water body extent changes, on a seasonal and interannual basis. Imagery data from Landsat and Terra/ASTER satellite sensors are processed to evaluate the water abundance on ground surface and the results are also used to validate radar altimetry observations. The results indicated that the classification scheme developed in our study is capable of quantifying the water proportion of land surface by the analysis of the backscattering coefficient and waveform data from T/P, towards studying of hydrological processes in the PPR of North America. Based on statistic analysis, trend and seasonality of Topex data over our testing sites are significantly correlated to simultaneous hydrological variation of wetlands.