Abstract

This hydrogeological study is part of the project "Study of groundwater in the Ubaté and Chiquinquirá valleys," implemented by the Hydrogeology Division of Ingeominas (Colombia) in collaboration with the Groundwater Research Service of TNO (The Netherlands).

Based on the data already provided by the research carried out in this project, such as geological, geoelectrical, hydrochemical, hydrological, and climatological data, and the results of the pumping tests carried out in the wells drilled during the project, in addition to the data provided by the inventory of wells, cisterns and springs in the region under study, as well as measurements of groundwater levels, the subsoil of the area in question is classified according to hydrogeological characteristics (Chapter 4) and a description of the groundwater system is given (Chapter 5). The groundwater resource assessment is presented mainly in a qualitative form; the available information does not justify quantitative conclusions regarding the overall possibilities for groundwater exploitation in the studied area. The results of this study are largely presented in the hydrogeological map.

In the Ubaté and Chiquinquirá area, there are Quaternary sediments and Tertiary and Cretaceous sedimentary rocks, divided into three classes of hydrogeological units (1, 11, 111). Class I represents unconsolidated Quaternary sediments. Within this class, hydrogeological units 11 and 12 refer to parts of the Quaternary fluvial-lacustrine deposits in which semi-confined aquifer levels can be found, exploitable using wells.

Class 11 refers to Tertiary and Cretaceous consolidated rocks subdivided into two hydrogeological units (111 and 112). Unit 111 indicates aquifers composed of the permeable sandstones of the Cacho Sandstone and the Tender Sandstone and Raizal Sandstone Members of the Guadalupe Formation, which may offer economic possibilities for groundwater exploitation through wells. The entire Chiquinquirá Sandstone Formation is classified as unit 111; the Middle Level of this formation forms a fractured sandstone aquifer that is considered exploitable by wells.

Class III also includes consolidated Tertiary and Cretaceous rocks. In contrast to class 11, class 111 represents only geological units mostly classified as aquitards, which are of little consideration for future groundwater exploitation using wells. This class refers to the following geologic units: the Chipaque Formation (1111); the Labor and Plaeners Sandstone Member of the Guadalupe Formation (1112); the Bogotá and Guaduas Formations (1113); the Los Pinos Member of the Guadalupe Formation; and the San Gil Formation (1114).

The best groundwater exploitation possibilities are found in the Quaternary aquifers (Units 11 and 12) east of Ubaté, west of Boquerón de Lenguazaque, east of Simijaca, and east-northeast of Chiquinquirá. Production per well is more than 1 liter per second in the case of Unit 11 and less than one liter per second in the case of Unit 12.

The concentration of iron in groundwater is generally high, and therefore, treatment is necessary to ensure its potability.

The groundwater potential of the study area is limited and does not lend itself to large-scale exploitation. However, it is sufficient in some cases to supply drinking water to small population concentrations.

Further research is recommended to improve knowledge of the resource.