Ana Cristina Oliveira Cancoro de Matos

Time-variations of equivalent water heights'from Grace Mission and in-situ river stages in the Amazon basin

Gravity Recovery and Climate Experiment (GRACE) mission is dedicated to measuring temporal variations of the Earths gravity field. In this study, the Stokes coefficients made available by Groupe de Recherche en Geodesie Spatiale (GRGS) at a 10-day interval were converted into equivalent water height (EWH) for a ~4-year period in the Amazon basin (from July-2002 to May-2006). The seasonal amplitudes of EWH signal are the largest on the surface of Earth and reach ~ 1250mm at that basins center. Error budget represents ~130 mm of EWH, including formal errors on Stokes coefficient, leakage errors (12 ~ 21 mm) and spectrum truncation (10 ~ 15 mm). Comparison between in situ river level time series measured at 233 ground-based hydrometric stations (HS) in the Amazon basin and vertically-integrated EWH derived from GRACE is carried out in this paper. Although EWH and HS measure different water bodies, in most of the cases a high correlation (up to ~80%) is detected between the HS series and EWH series at the same site. This correlation allows adjusting linear relationships between in situ and GRACE-based series for the major tributaries of the Amazon river. The regression coefficients decrease from up to down stream along the rivers reaching the theoretical value 1 at the Amazons mouth in the Atlantic Ocean. The variation of the regression coefficients versus the distance from estuary is analysed for the largest rivers in the basin. In a second step, a classification of the proportionality between in situ and GRACE time-series is proposed.

ANALYSIS OF WATER MASS VARIATION IN WETLANDS REGIONS USING DATA FROM GRACE SATELLITE MISSION: THE PANTANAL CASE

ABSTRACT. The natural heritage of biodiversity of the Paraguay river basin is subject to potential impacts due to climate change. To monitor these environments at large spatial scales, the satellite gravity mission GRACE (Gravity Recovery and Climate Experiment) provides time-variable Earth’s gravity field models that reflect the variations due to mass transport processes, like continental... Keywords : water storage, satellite gravity mission, river gauge, rainfall. RESUMO . O patrimonio natural de biodiversidade da bacia do rio Paraguai esta sujeito a potenciais impactos das mudancas climaticas. Para monitorar esse ambiente em escala espacial, a missao satelital GRACE (Gravity Recovery and Climate Experiment) fornece modelos do campo de gravidade da Terra variaveis no tempo devido ao processo de transporte de massa, como as variacoes de armazenamento de agua... Palavras-chave : armazenamento de agua, missao satelital, cotas do nivel d’agua, precipitacao.

Water Level Temporal Variation Analysis at Solimões and Amazonas Rivers

The Amazonas and Solimoes rivers and their tributaries represent the largest river system in the world. It involves an extremely high water volume, discharging into the Atlantic Ocean approximately 20% of the total water volume of the whole world. The main factor which influences the water level is the intensive rainfall over those regions, consequence of the humid characteristic of the tropical climate. This paper is intended to show water level variation along both Solimoes and Amazonas rivers as a direct consequence of three different kinds of ocean-atmosphere interactions: El-Nino, La-Nina and the inter-hemispheric Sea Surface Temperature – SST gradient into the Atlantic Ocean. For this study it has been used 13 limnimetric stations where geodetic heights were derived from GPS observations combined with GEOAMA (Amazon geoid model), developed at Laboratory of the Topography and Geodesy (LTG). The orthometric height of the water surface was derived. The variation of water level measurements from 1993 through 2006 has been analysed for the greatest flood and the lowest ebb periods, June and October respectively. This study allowed to calculate the river gradient in the mentioned period.