Paper Number: 1422
Groundwater Dynamic in a period of drought - alluvial plain of Mogi Guaçu River, Sao Paulo, Brazil.
Pereira, S.Y.1, Pereira, P.R.B.2 and Ricardi-Branco, F.S.3
1University of Campinas, Geosciences Institute, Geology and Natural Resources Department. 51, Joao Pandia Calogeras Street, Campinas – Sao Paulo, Brazil, sueliyos@ige.unicamp.br .
2Sao Paulo Secretariat of Environment, Forestry Institute. 931, Horto Street, Sao Paulo – Sao Paulo, Brazil, paulobrumpereira@gmail.com
3University of Campinas, Geosciences Institute, Geology and Natural Resources Department. 51, Joao Pandia Calogeras Street, Campinas – Sao Paulo, Brazil, fresia@ige.unicamp.br.
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Shallow aquifers are responsible
for supporting the Savannah and Semideciduous forests that occur in wide
plains in Brazil. In long periods of drought, the decay of groundwater
levels may affect these forests. The study area has 4 km2 and
localizes in the floodplain of the Mogi Guaçu River in the EEcMG
(Ecological Station of Mogi-Guaçu). The research aimed to understand the
dynamics of groundwater in periods of drought. In the hydrographic basin
of the Mogi-Guaçu River, the average annual temperatures range from
20.5°C to 22.5°C, and the average annual rainfall varies from 1,400 to
1,600 mm. In the rainy season (October to March), the average
precipitation accumulated varies from 1,100 to 1,250 mm, and in the dry
season (April to September) from 250 to 300 mm [1]. The Alluvial
Semideciduous Forest occurs predominantly along the Mogi-Guaçu River.
Two areas of Wet Field are located within the EEcMG, and they present
some grass coverings [2]. 20 monitoring wells were installed in
terraces, recent plains, abandoned meanders, and Wet Field. The
sediments of the aquifer show medium sandy texture, and hydraulic
conductivity ranged from 3.83 X 10-6 m/s to 1.03 X
10-3 m/s [2]. The results of monitoring water table levels
held in September 2015 represent the dry season of a period that lasted
two years in the region. Figure 1 shows groundwater flow of higher areas
to the north towards the south (effluent behavior of Mogi Guaçu River).
Wet Field presents shallow water level (less than 2 meters depth) in the
middle of the plain. In general, the water table level reached more than
5 meters depth (in some places got around 15 meters depth) in terraces
and recent plains close to the river, affecting the undergrowth. During
this drought period, Comprido creek fed and maintained the Wet Field,
but in terraces and recent alluvial plain a no-recharge condition was
observed. * FAPESP 2013/22729-2.
Figure 1: Mogi Guaçu alluvial plain – on the left, potentiometric map; on the right side, water level map - September 2015 (dry season).
References:
[1] CBH-Mogi - Mogi-Guaçu river Watershed Committee. [1999]. Technical Report. 252 pp.
[2] Ricardi-Branco, F.S. et al. [2015]. In: Springer Earth System Sciences. 1ed., p. 667-705.