BGR Bundesanstalt für Geowissenschaften und Rohstoffe

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TC Supraregional: Sustainable Use of the Transboundary Groundwater Resources of the Guaraní Aquifer System (GAS-PY)

Report of the project:

Location and extension of the Guaraní Aquifer and project organisationOutline map and project organisation Source: BGR

The Guaraní Aquifer System (Sistema Acuífero Guaraní, SAG) in South America extends over an area of about 1.1 million km² and underlies one third of the La Plata Basin. The SAG is formed by sandstones, which are regionally covered by basalts. The estimated volume of fresh groundwater amounts to 30,000 km³, and thus the SAG represents one of the largest groundwater reservoirs of South America. The groundwater system is shared by Argentina (21% of the land surface), Brazil (68%), Paraguay (8%) and Uruguay (3%) showing a population of 90 million inhabitants in that region, with a majority in population and groundwater production in Brazil.

The SAG is supposed to play a vital role in the current and future regional water supply. In relation to this strategic importance, a multinational project "Environmental Protection and Sustainable Development of the Guaraní Aquifer System" has been initiated by the Global Environment Facility (GEF) and was supported by the World Bank (WB). The overall project target was to form the technical and institutional platform for a most suitable, sustainable groundwater management and protection. Starting in May 2003, the project has been executed during six years by the Organization of American States (OAS) through the General SAG Secretariat in Montevideo (Uruguay) and in close cooperation with the four national executing units. The project has been under the control and the political guidance of the steering committee. On a long term, all project results served safeguarding the interests of future generations.

Location and cross sections of the Guaraní AquiferLocation and cross sections of the Guaraní Aquifer Source: BGR

At present, groundwater from the SAG is pumped pre-dominantly at the sandstone-outcrop areas where the depth to the water table is low to moderate. The quality of the mainly unprotected groundwater is already endangered by anthropogenic influences e.g. by pollution from urban centres and from the agriculture at an industrial scale. Furthermore, the water demand is increasing as a result of the rapidly growing urbanisation; in total an enhanced exploitation of the transboundary groundwater resource is predictable. For the sustainable use, management and protection of the SAG common activities by the adjacent states are imperatively needed before negative impacts will occur.

The SAG sandstones have been formed during the Triassic to Jurassic age (roughly 250 to 145 million years B.P.) and were overlaid during the Cretaceous age (145 to 130 million years B.P.) by volcanic material (basalt of the geological formation Alto Paraná in Paraguay and Serra Geral in Brazil). Regionally the basalt cover can reach a thickness of more than 1000 metres. In the central and northern parts of the SAG the basalts are superimposed by sandstone formations of younger Cretaceous age which are known as Acaray formation in Paraguay and as a formation of the Baurú group in Brazil. The SAG sandstones have different regional names: Botucatú in Brazil, Misiones in Paraguay and Tacuarembó in Argentina and Uruguay. Only after 1990 the same hydrogeological significance of these sandstone formations was recognized and unified by the name "Guaraní Aquifer".

Settlement areas of the indigenous population and mean annual rainfall in ParaguaySettlement areas of the indigenous population Source: BGR

The name "Guaraní (Aquifer)" has been chosen also in remembrance, honour and respect to the indigenes people, especially to those from the Guarani language family, who had their homelands in the SAG area originally. In Paraguay the Guaraní people’s settlements are concentrated to the oriental region of the country. Present living conditions in Argentina, Brazil and Paraguay are comparable to each other and are characterized in general by low standards in education, employment and basic domestic supply, e.g., with water and electricity.

On behalf of the German Ministry for Economic Cooperation and Development (BMZ) the Federal Institute for Geosciences and Natural Resources (BGR) supported the SAG-GEF project through assisting Paraguay to meet the requirements from the SAG-GEF project in the fields of hydrogeology and groundwater resources evaluation and prognosis, and through direct advice to the SAG-GEF project, e.g. in the formulation of recommendations concerning the groundwater management of the complete aquifer system.

Hydrogeological situation and model resultsHydrogeological situation and model results Source: BGR

Within the frame of technical cooperation the project SAG-PY has been run between BGR and the Ministry of Environment SEAM (Secretaría del Ambiente, Dirección General de Protección y Conservación de los Recursos Hídricos, DGPCRH) as the direct partner in Paraguay. By the project activities Paraguay (via SEAM) has strengthened its role as a reliable partner on a par with the international water community. The SAG-PY project results are considered as Paraguay’s national contribution to the SAG-GEF project.

The compilation of all relevant hydrogeological and other data has been summarised in a digital base map of the oriental region of Paraguay and has been supplemented by several thematic maps. Field activities, including investigations on hydrochemistry and isotopes hydrology, have improved the knowledge about the Guaraní aquifer in Paraguay. Based on the hydrogeological conceptual model, a numerical groundwater simulation model has been developed. This model calculates the groundwater flow and allows the quantification of the groundwater resource. Due to the geohydraulic reasons of a transboundary aquifer situation, the model investigation area includes parts of the neighbouring countries of Brazil and Argentina. Ultimately, the results from the model calibration and from predictive simulations form the basis for the development of strategies in groundwater management and protection. Further on, the project SAG-PY has contributed countrywide to a better awareness of the vitally important resource water, in particular of the groundwater from the Guaraní aquifer.

Transboundary groundwater management of Pedro Juan Caballero and Ponta PorãTransboundary groundwater management Source: BGR

The SAG-GEF project has initiated the fundamentals for a common groundwater management in the Guaraní region, and in August 2011 the four partner countries Argentina, Brazil, Paraguay and Uruguay have concluded a multilateral contract about a strict cooperation in Guaraní groundwater policy and management. By this, the strategic action plan (PEA) developed by SAG-GEF and also in collaboration with BGR has got a realistic background: the countries are establishing the SAG coordinating unit under the umbrella of the La Plata Commission (CIC) in Buenos Aires, in order to facilitate common pilot projects. One of the future pilot projects with a high priority will be related to the groundwater transboundary situation between Paraguay and Brazil.

Effective groundwater production from the Guaraní Aquifer in Ponta Porã in BrazilGroundwater production in Ponta Porã Source: BGR

A favourite economic development and the rapid growth of population cause a dramatic stress on the groundwater resources of the shallow basalt aquifer. Additionally, environmental and groundwater pollution complicate the supply of more than 200,000 people with clean water at a sufficient quantity. For this reason Ponta Porã has already started with groundwater production from the subjacent SAG. Because of the drawdown effects at a regional scale the twin community intends to practise a common transboundary groundwater management, in accordance to the spirit of the "Guaraní agreement". The political will has been communicated during several workshops with participants from both countries. The partners intend also to facilitate a bilateral hydrogeological study after establishing a water commission and as the precondition for future common groundwater management. It is obvious that the rehabilitation of the shallow basalt aquifer is of prior importance and the implementation of a central sewage collector and treatment system is of urgent need.

Concluding remark:

By various activities and within an international framework the project SAG-PY has contributed to the protection of the Guaraní aquifer system. Approaches to a sustainable transboundary groundwater resources management serve to the supply of future generations.


Partner: "Dirección General de Protección y Conservación de los Recursos Hídricos (DGPCRH)" of the Secretaría del Ambiente (SEAM)


Literature:

Leader:

Further Reading:

Maps:


Contact:

    
Dr.-Ing. Sara Ines Vassolo
Phone: +49-(0)511-643-2818

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