M-05 – ALMONDA AND ALVIELA KARSTIC SPRINGS
Main organizer: Albino Medeiros (AIH-GP)
Co-organizer: José Crispim (FCUL)
Maciço Calcário Estremenho (MCE), is a geomorphologic unit with well-defined limits. It is mostly formed by middle Jurassic limestones. In the west, the Candeeiros mountain emerges abruptly from the platform of Aljubarrota reaching approximately the altitude of 600 m over a length of about 30 km; the southern and eastern slopes contact with terrains of the tertiary Tagus Basin along an extensive fault scarp.
The discharge regime of the main springs presents very rapid and significant changes. The main springs are located at the limits of the massif at the contact with the less permeable rocks of Tertiary and Cenozoic. Almonda and Alviela springs are located in eastern and southern margin.
The spring of "Olhos de Água do Alviela" is the most important of all MCE. Its maximum discharge is over 1 Mm3/day and the dry season discharge is very seldom below 30 000 m3/day. The mean annual discharge is 120 Mm3/year. The spring used to be one of the most important contributors in water supply to the Lisbon region through an aqueduct 120 km long.
Following in importance the aforementioned spring are the Almonda spring. The data available do not allow an estimate of the total discharge. By comparison with Alviela the total discharge of Almonda spring could be between 80 and 100 Mm3/year.
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