HU - Hydrogeology and Environment

Journal of the Dept. of Hydrogeology and Environment, University of Würzburg (ISSN 09309-3757)

Editorial office: BGI, Greisingstr. 8, 97074 Würzburg, GERMANY

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Vol. 34 (In print: 2005)


Vol. 34: 

Origen y Dinámica del Agua Subterránea en el noroeste del Chaco Sudamericano

[Origin and dynamics of groundwater in the northwestern Chaco in South America]

Ronald C. Pasig

The "Gran Chaco Americano" region represents one of the largest and most important ecosystems in the South American continent. This thesis research study is concentrated on the northwestern sector of this immense area, the so-called Chaco Tarijeño region in the southwest of Bolivia and the western sector of the Paraguayan Chaco. The total area included in this research project covers approximately 70.000 km2, of which 80% are to be found in Paraguyan territory and 20% in Bolivian territory. The climate is semi-arid, with average annual temperatures of 25 degrees centigrade and average rainfall of some 700 mm per year. Only the Pilcomayo River runs through the region as a permanent shallow river-bed from northeast to southeast, forming at the Ibibobo military base, a large alluvial cone covering approximately 200.000 km2 and extends inclusively as far as the active river-bed of the Paraguay River in its eastern limits.
The limitating factor for human, agricutural and livestock development in the Chaco region is the lack of good quality water sources in sufficient quantities. There are scarce and seasonally limited shallow water resources, provided mainly by existing streams and rivers. In the meantime this signifies that groundwater resources are found to not be sufficiently explored and in fact the existence of such sources are little known.
In order to increase and improve the hydrological knowledge of this area, data provided by different existing studies of the subject have been examined and analyzed. This data has been the groundwork for this doctoral thesis research study called "Origin and Dynamics of groundwater in the northeast South American Chaco (Chaco Tarijeño and western Paraguayan Chaco).
Isotopical and hydrochemical interpretations allowed predictions about the origin and dynamics of groundwater to be carried out, as well as currently, as in previous more humid paleoclimatic ages. Similar interpretations were obtained by means of geohydraulic analysis. The hydrogeological simulation model MODBIL (Udluft, 2000 ff) has been implemented with the objective of obtaining by a methodically separated way, the rechargeable values of groundwater, shallow and sub-superficial draining and evapo-transpiration of different regions of the Chaco Tarijeño. The synoptic table of all the results analyzed in separate ways, has allowed the carrying out of a precise and reliable hydrogeological balance. Complementarily, a detailed analysis of the hydrogeological information of the central Paraguayan Chaco has been effected, with the objective of increasing and improving knowledge of the salinization problem of the water and soil in the region.

Paper language: spanish; german abstract


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