Abstract
Variations in surface water extent and storage are poorly characterized from regional to global scales. In this study, a multi-satellite approach is proposed to estimate the water stored in the floodplains of the Orinoco Basin at a monthly time-scale using remotely-sensed observations of surface water from the Global Inundation Extent Multi-Satellite (GIEMS) and stages from Envisat radar altimetry. Surface water storage variations over 2003–2007 exhibit large interannual variability and a strong seasonal signal, peaking during summer, and associated with the flood pulse. The volume of surface water storage in the Orinoco Basin was highly correlated with the river discharge at Ciudad Bolivar (R = 0.95), the closest station to the mouth where discharge was estimated, although discharge lagged one month behind storage. The correlation remained high (R = 0.73) after removing seasonal effects. Mean annual variations in surface water volume represented ~170 km3, contributing to ~45% of the Gravity Recovery and Climate Experiment (GRACE)-derived total water storage variations and representing ~13% of the total volume of water that flowed out of the Orinoco Basin to the Atlantic Ocean.
Highlights
Terrestrial waters represent less than 1% of the total water stored on Earth, play a major role in climate variability and are necessary for sustaining terrestrial life and human needs
We present a multi-year analysis of inundation at both seasonal and interannual time-scales over 1993–2007, a validation of altimetry-based water levels located along the Orinoco main stem and its major tributaries and an estimation of the surface water storage that we evaluated against in situ and remotely-sensed hydrological information, including river discharge, rainfall and total water storage, based on gravimetry from space data
This study presents an analysis of the surface water extent (1993–2007) and storage (2003–2007) in the floodplains of the Orinoco Basin at a spatial resolution of ~25 km
Summary
Terrestrial waters represent less than 1% of the total water stored on Earth, play a major role in climate variability and are necessary for sustaining terrestrial life and human needs. Among the various reservoirs in which fresh water is stored (e.g., ice caps, glaciers, snowpack, soil moisture and groundwater), surface waters (rivers, lakes, reservoirs, wetlands and inundated areas) play a crucial role in the global biogeochemical and hydrological cycles [1,2] Among these hydrological reservoirs, wetlands and floodplains have a substantial impact on flood flow alteration, sediment stabilization, water quality and groundwater recharge and discharge [3,4], even though they cover only about 6% of the Earth’s surface [5]. During its stay in these permanent and temporary inundated areas, water is delayed in its transit to the sea and subject to evapotranspiration, and often undergoes large biogeochemical changes due to sedimentation, nutrient uptake by biota and modifications of redox conditions [14,15,16] Water storage in these wetlands and their outflows represents a significant part of the water balance in the basin [17,18,19]
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