Groundwater Resources of Península Valdés

Abstract

In this chapter, the groundwater resources of Península Valdés are analyzed in order to recognize the influence of the late Cenozoic stratigraphic record and the geomorphology on the hydrogeology of the region. The geology of the study area defines a hydrogeological sequence that begins with a non-saturated zone of variable thickness and an essentially aquifer-like behaviour. Under the non-saturated zone there is a phreatic aquifer within the Quaternary deposits or in the sandstones of the Puerto Madryn Formation, and below it, one or more semi-confined or confined aquifers in the same formation or in the underlying Gaiman Formation. The aquifer levels located in the Puerto Madryn Formation are main water supply that supports the farming activities in the region. The groundwater hydrodynamic and the associated hydrochemical and isotopic characteristics are closely related to the climate and to the relationship between the geomorphology and lithology of the region. As climate is quite homogeneous all over the peninsula, the different relationships between the geomorphological and lithological unit allows to define four hydrogeological regions: (1) Aeolian landforms, which represents the main recharge zone with the low salinity waters; (2) Terrace levels, as the circulation area with high salinity waters, (3) Endorheic depressions that are the inland discharge sector where the evaporation is the dominant process and hypersaline playa lakes occurs, and (4) Coastal systems which represents both the regional discharge area as well as the local recharge zone with low salinity groundwater reservoirs.

Glossary

Aquicludes

Rocks or unconsolidated material of low hydraulic conductivity which yield inappreciable quantities of water to drains, wells, springs and seep

Aquifer

Permeable water-bearing rocks or unconsolidated material capable of yielding exploitable quantities of water

Aquifuges

Rocks or unconsolidated material that cannot absorb or transmit water

Aquitard

Rocks or unconsolidated material that transmits water at a very slow rate compared with an aquifer

Clast-supported

Conglomerate or sand in which most individual clasts are in contact with each other. The matrix (finer material between the gravel clasts, such as sand, silt or mud) fills the spaces between the clasts

Confined aquifers

Aquifer overlain and underlain by an aquifuge, aquiclude or acuiclude

Hydraulic conductivity

Is a measure of the soil ock or unconsolidated material’s ability to transmit water when submitted to a hydraulic gradient. 

Matrix-supported

Conglomerate or sand where the individual clasts are held together by the matrix (i.e. they are not necessarily in contact with each other). The rock may appear disorganized without any clear internal structure

Non-saturated zone or unsaturated zone

Portion of the lithosphere in which the interstices are filled partly with air and partly with water

Phreatic aquifer

An aquifer that is physically in contact with the atmosphere through the groundwater surface

Piper plot

Ternary diagram useful to visualize the chemistry of a rock, soil, or water sample. The apex of the diagram include major cations and anions founded in nature

Saturated zone

Zone of the water-bearing material in which all voids, large and small, are filled with water

Semi-confined

Aquifer overlain and/or underlain by a relatively thin semi-pervious layer, through which flow into or out of the aquifer can take place