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Heterogeneity effects in soil water tranferences process under unsaturated conditions in alluvial soil in the mesoscale

IWRA World Water Congress 2017 - Cancun Mexico
5. Water ecosystems and physical regimes
Author(s): Rodrigo Peronico
Ana Emília Rabelo
Artur Coutinho
Severino Santos Neto
Tassia Melo
José Angelim Silva Neto
Edevaldo Alves Rodrigo Peronico
IFAL/UFPE
rodrigo.lustosa@ifalpalmeira.edu.br
Ana Emília Rabelo
UFPE
anaerabelo@gmail.com
Artur Coutinho
UFPE
arthur.coutinho@yahoo.com.br
Severino Santos Neto
UFPE
martinsdsn@gmail.com
Tassia Melo
IFPB
melo.tassia@yahoo.com.br
José Angelim Silva Neto
UFPE
joseangelim@yahoo.com.br
Edevaldo Alves
UFPE
edevaldofisica@gmail.com
Antônio Antonino
UFPE
acdantonino@gmaail.com


Keyword(s): Ground Penetrating Radar; Tridimensional Infiltrometer; Hydrus; Vadose Zone; Preferential Flow.
Article:

Abstract

Alluviums are geological units of fundamental importance for water supply in semi-arid regions of northeastern Brazil. Characterizing alluvial aquifers becomes a key action in the sustainable management of already scarce water resources in the region. Generally, to quantify the storage capacity of these sites and aquifers recharge the hypothesizes that the soil is homogeneous at the field scale or at the mesoscale are adopted. This context neglects the impacts that a heterogeneous profile can cause in the vadose zone flows processes. It can lead to estimation errors putting at risk those water resources so important for the diffuse population. This paper presents a hydrodynamic modeling of the unsaturated zone with a heterogeneous profile in a soil alluvial in the Capibaribe River Basin - Pernambuco - Brazil. Threedimensional infiltration tests were carried out, using single ring infiltrometers of 8.2 cm diameter at different depths of the soil and 100 cm in diameter to evaluate the influence of heterogeneity on the water flow in the field scale. The collected data were used to determine the hydrodynamic properties of the soil with the aid of the Beerkan method with the BEST algorithm. The soil profile was represented by the mapping performed with the ground penetration radar (GPR) and later built in the Hydrus model, considering a heterogeneous and bidimensional simulation profile. The following scenarios were adopted for the modeling: events of internal drainage, variable flow and infiltration tests. An equivalent profile model was proposed to study the phenomenon of soil water transfer in a simpler way, providing a representative equivalent curve for the profile. This model had a good adjustment, generating water transference predictions close to the real. However, it cannot be used to evaluate the behavior of preferential flows of the soil, since it does not quantify sectors, but rather the entire profile. It was observed that, in a heterogeneous soil profile, hydraulic barriers could be created due to pore connectivity factors and distinct water retention between the layers and, consequently, to generate suspended groundwater. Finally, an empirical model of deep drainage flow was proposed, based on hydrodynamic soil data to quantify possible volumes of water drained by a flow or constant pressure event at the soil surface.

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