TC Bolivia: CABAS Project - Improvement of the Ability of the Bolivian Geological Survey to Explore for Groundwater Resources
Report of the project:
- Bolivia - Strengthening the Hydrogeology Department of the Servicio Nacional de Geología y Minería
- Bolivien - Stärkung der Hydrogeologischen Abteilung des Servicio Nacional de Geología y Minería
Background
Source: BGR
In the rural areas of Bolivia, agriculture is the most important source of income. In many cases, agricultural production is limited by the lack of water for irrigation. This limit to agricultural income has led to massive migration from some rural areas. For example, the dry Chaco Tarijeño and the area around the Uyuni salt lake. This massive migration leads to uncontrolled growth of the cities. Insufficient regional planning leads to largely uncontrolled use of the groundwater resources. No governmental agency has the expertise or authority to assess groundwater resources and develop guidelines for their management. Emphasis is placed, therefore, on increasing the scientific and administrative capabilities of the counterpart agency.
Objectives
The long-term objective of the project is to improve the supply of water to the urban and rural population by properly planning the development and protection of the groundwater resources. The CABAS (Convenio Alemán-Boliviano de Aguas Subterráneas) project is being conducted by BGR and its counterpart agency, the Department of Hydrogeology (Departamento de Hidrogeología) of the Bolivian Geological Survey and Bureau of Mines (Servicio Nacional de Geología y Técnico de Minas, SERGEOTECMIN). The Department of Hydrogeology of SERGEOTECMIN and associated organizations whose task is to explore for, assess, and develop groundwater resources are to be strengthened by sharing scientific knowledge and experience and modern technical and methods know-how and equipment. This is done in on-the-job training, seminars, and post-graduate courses.
The main areas in which work is being done to improve the qualifications of the SERGEOTECMIN staff are
- hydrogeological surveys,
- geophysical surveys,
- remote sensing,
- development of a hydrogeological database,
- preparation of hydrogeological maps, and
- development of a basis for the legal framework for the management and protection of groundwater resources.
The on-the-job training is concentrated on the development and management of groundwater resources in selected areas of Bolivia: in the Cochabamba basin, the Chaco Tarijeño, the Pampas de Lequezana near Potosí, and to a lesser extent in the area around Uyuni salt lake and the Tarija urban area.
Rapid population growth and a lack of regional planning in the Cochabamba Valley have led to largely uncontrolled use of the groundwater resources. In this area, planning documents are urgently needed. Agricultural development in the Chaco Tarijeño is limited by the low precipitation rate. There is a lack of knowledge about the limited groundwater resources. The Pampas de Lequezana is a major potato growing area. As in the Chaco region, an improved water supply is of decisive importance for sustainable development of agriculture in the region.
Results
The following results have been attained:
Valle Central de Cochabamba: The Central Cochabamba Valley, at an elevation of about 2500 m in the eastern Andes, covers about 1150 km². Cochabamba, the third largest city of the country with a population of about 600,000, is in this valley.
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- A network of 37 groundwater observation wells (some of them as production wells) has been set up. Measurements have been made monthly since 1991. The data show that the aquifer is not overused. The groundwater table has not fallen in this time period. An annual cycle of groundwater levels results from the low summer rainfall.
- Chemical and bacteriological analysis of samples from 50 wells shows that the deeper groundwater is generally of good drinking water quality. Water from shallow aquifers sometimes shows some contamination.
- Information about the sediments in the valley basin was obtained from geoelectric measurements in the valley: The margins of the course-grained talus fans were determined. It was found that the sediments become increasingly fine-grained with increasing depth, i.e., they become increasingly less permeable. A map of areas with conditions favorable for the development of groundwater resources was made on the basis of the geoelectric data.
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- A 300-m-deep borehole (Cb-308) was drilled to investigate the quality of the groundwater at this depth. In general, deep groundwater is less contaminated than near-surface groundwater and is thus more suitable for drinking water. However, the hydraulic properties of the deep aquifer were found to be unsuitable for development. Therefore, groundwater from shallower aquifers (less than 200 m depth) must be the principal source of drinking water, making groundwater protection all the more necessary.
- Hydrogeological maps: Two hydrogeological maps with explanatory notes were prepared as part of the map series "1 : 250,000 Thematic Maps of Mineral Occurrences in Bolivia". During the preparation of the Cochabamba and Uncía map sheets, Bolivian hydrogeologists were trained to continue the project independently.
- A hydrogeological database was set up in the counterpart agency. Relevant data was entered in the database; the data was visualized on maps and in graphs and used for reports.
More information on the hydrogeology of the Central Cochabamba Valley ...
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Chaco Tarijeño: The Chaco Tarijeño region (c. 14,000 km²) is the southeast corner of Bolivia on the border to Paraguay and Argentina. Tertiary alluvial deposits cover the Chaco Tarijeño plain, which gradually falls from an elevation of about 500 m in the west near Villamontes to about 280 m in the east. The plain is crossed from the NW to the SE (about 150 km) by the Rio Pilcomayo.
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- Working together with the counterpart agency, a network of weather stations was set up in the Chaco Tarijeño. Precipitation between 1992 and 1996 varied from 300 mm in the eastern part of the Chaco to 900 mm in the west. In the Andes foothills to the west, values as high as 1100 mm were measured.
- Geoelectric soundings were made to determine the distribution of fresh water and the location of the fresh water/saline water boundary.
- Isotope hydrological analyses showed that the groundwater in the Chaco is recharged in the Andes foothills to the west, from where it flows to the east in the relatively deep, fine-grained, Tertiary and Quaternary sediments. Well yields in the Chaco range between 0.5 and 5 L/s. The groundwater is locally saline, in most areas, however, the groundwater is of sufficient quality for any use. A 1 : 250 000 hydrogeological map with explanatory notes was prepared.
- A hydrogeological database was set up in the counterpart agency.
More information on the hydrogeology of the Chaco Tarijeño ...
Pampas de Lequezana: This region is approx. 40 km east of Potosi in the eastern Andes. The study area covers about 130 km² on a peneplain at elevations between 3200 and 3300 m.
- Working together with the counterpart agency, a network of groundwater observation wells was set up in the Pampas de Lequezana. Ten stations for measuring precipitation were installed. An initial groundwater balance indicates a very low groundwater recharge rate. Increasing use of motorized pumps is leading increasingly to high-input agriculture; thus there is the danger that the aquifers will be pumped in excess of recharge.
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Literature:
Project activities and results were particularly documented and published in around 60 technical reports and in volumes of the "Boletín del Servicio Nacional de Geología y Técnico de Minas (SERGEOTECMIN)".
- HUARANCA, R. & NEUMANN-REDLIN, CHR. (1998): Mapas Temáticos de Recursos Minerales de Bolivia: Mapa Hidrogeológico y Memoria Explicativa, Hoja Cochabamba 1 : 250.000. - Boletín del Servicio Nacional de Geología y Minería (SERGEOMIN), 16: 75 pág., 8 fig., 19 fot., 8 tab.; Cochabamba.
- HUARANCA, R. & NEUMANN-REDLIN, CHR. (2000): Mapas Temáticos de Recursos Minerales de Bolivia: Mapa Hidrogeológico y Memoria Explicativa, Hoja Uncía 1 : 250.000. - Boletín del Servicio Nacional de Geología y Minería (SERGEOMIN), 33: 48 pág., 3 fig., 19 fot., 7 tab.; Cochabamba.
- NEUMANN-REDLIN, CHR., RENNER, S. & TORRES, J. (2000): Hidrogeología del Valle Central de Cochabamba, Bolivia.- Proc. of the 1. Joint World Congress on Groundwater, Fortaleza, Ceará, Brasil, July 31 - August 04, 2000. (PDF, 113 KB)
- PASIG, R. (1998): Estudio Hidrogeológico del Chaco Tarijeño de Bolivia. - Boletín del Servicio Nacional de Geología y Minería (SERGEOMIN), 15: 97 pág., 34 fig., 8 fot., 20 tab., 4 map.; Cochabamba.
- PASIG, R., VILLENA, H. & NEUMANN-REDLIN, CHR. (2000): Hydrogeology of the Chaco Tarijeño (Bolivia) .- Z. Angew. Geol., SH1 (2000), p. 201-205; Hannover. (PDF, 132 KB)
- RENNER, S. & VELASCO, C. (2000): Geología e Hidrogeología del Valle Central de Cochabamba. - Boletín del Servicio Nacional de Geología y Minería (SERGEOMIN), 34: 104 pág., 38 fig., 10 tab., 3 map.; Cochabamba. (PDF, 8 MB)
- STRAHL, J. (1998): Estudio Palinológico del Pozo de Perforación Cb 297 en el Valle Central de Cochabamba. - Boletín del Servicio Nacional de Geología y Minería (SERGEOMIN), 14: 77 pág., 7 fig., 97 fot., 2 tab.; Cochabamba.