José Geilson Alves Demétrio

Síntese da hidrogeologia nas bacias sedimentares do Amazonas e do Solimões: Sistemas Aquíferos Içá-Solimões e Alter do Chão

Geological maps and stratigraphic charts of the Amazon and Solimoes sedimentary basins were reviewed, emphasizing the formations Alter do Chao, Ica and Solimoes, the largest reserves of fresh groundwater in these basins. The lack of information on these formations was minimized by sample probe and stratigraphic profiles of construction, lithological and geophysical water and oil wells, obtained in the Base Operacional Geologo Pedro de Moura, Urucu region, about 650 km southwest of Manaus (AM). In the Amazon Basin, the Aquifer System Alter do Chao is characterized by unconfined and confined aquifers, with transmissivity between 1.5 and 9.1 x 10-3 m²/s, indicated for public supply. In the Solimoes Basin, this system is confined by Aquiclude Solimoes, recovered by the Ica-Solimoes Aquifers. The reserve is estimated as 33,000 km³. The Aquifer System Ica-Solimoes, in Urucu, is unconfined-confined, with two aquifers hydraulically connected: the superficial, with top and bottom at depths near 20 and 70 m, respectively; and the deeper, between 50 and 120 m. With an outcrop area of 948,600 km² in the Solimoes Basin, the reservation of this system was estimated as 7,200 km³, less expressive than the Aquifer System Alter do Chao. The average hydrodynamic parameters were: T = 3 x 10-3 m²/s, S = 5 x 10-4 and K = 1 x 10-4 m/s, orders of magnitudes similar to those found in the aquifer Alter do Chao. Assessing the interrelationships and potential of these two regional aquifers sought to contribute to the hydrogeological knowledge in the Amazon Basin region, where researches on groundwater are still incipient.