Hydrology
The Amazon Basin receives 11.87 x 10¹²m³/year of rainwater. It loses 6.43 x 10¹²m³ through evapotranspiration, and 5.45 x 10¹²m³/year through the Amazon River discharge. The average mass of water vapor in the Amazon is 24 x 10¹º tons.
Flooding is an important aspect of várzea hydrology. Near the coast, the Marajó várzea is influenced by tidal flooding. This tidal activity floods the Marajó twice daily. The Marajó has poorly drained, heavily mottled soils. Further inland, the Gurupa várzea is influenced by both tidal and seasonal flooding. The daily flood level can be from 4-7 m when the seasonal flood pulse is greatest, and 2-3 m when the seasonal flood is lowest. This constant fluvial activity has created intricate sedimentary islands, and the várzea is called "region of the islands." The other three várzea, Iquitos, Monte Alegre, and Purus, are further inland. They typically flood for up to 8 months (Iquitos is up to 10 months) per year.
Considering this flooding, it is very clear how the sediment rich rivers of the amazon influence the várzea. This sediment originates from nutrient rich sediment in the Andes, and it is for this reason that the várzea are so desired for agriculture. This could also be part of why várzea are so biodiverse.
Flooded Trees Seasonal Water Levels
(click to enlarge)
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