versão impressa ISSN 0001-3765
An. Acad. Bras. Ciênc. v.72 n.2 Rio de Janeiro jun. 2000
PANTANAL WETLAND RIVERS AND LAKES WATER LEVEL MONITORING USING TOPEX-POSEIDON SATELLITE ALTIMETRY: PRELIMINARY RESULTS
Elaine Medeiros de Mattos* and Naomi Ussami
Departamento de Geofísica, Instituto Astronômico e Geofísico, Universidade de São Paulo.
Presented by IGOR G. PACCA
Topex-Poseidon radar altimetry operating since 1992 was originally designed to study large scale oceanographic processes with high accuracy. Satellite repeating tracking period is almost 10 days. Topex sensor data over continental areas have been used to monitor water level variations over large lakes and rivers in remote areas, where gauge stations are not available or water-level data are not easily accessible (Birkett, C.M., 1998, Water Resour. Res., 34, 1223). Along track data are ~500m spaced and the average lateral track spacing is ~350km near the equator. In the present work we discuss the results of monitoring three different sites within the Pantanal Wetland, SW Brazil, between years 1993 and 1998, using the averaged altimeter data. Site number one is a large lake located on the eastern margin of the Paraguay river, close to Ladario gauge station. Water layer is more than 3-m thick and the accuracy in measuring water level variation is ±12cm. Site number two is separated from site one by ~350km and it is located between Cuiabá and São Lourenço rivers. In this area, a larger dispersion in measured data is observed due to the size of water body and a more complex reflected signal waveform possibly caused by the topographic interference. In spite of this dispersion, it is still possible to recognize a time shift of 3 months in the maximum-minimum water levels between sites one and two. In areas where the water layer is less than 0.5m, large scatter of altimeter data is observed during the dry season. In those areas it is only possible to discriminate between dry and wet periods. The use of radar waveform data (echo) can improve the estimate of water level variation. Better lateral coverage can be obtained by using radar altimeter data from ERS 1/2 missions but in this case, the repeating period is 35 days.
( November 19, 1999 ) .
* FAPESP Scholarship (I.C. # 98/07682-8).