Recarga de sistemas lénticos en zonas de páramo casi de estudio: Origen de la recarga del sistema laguna negra,localizada en el páramo de ocetá a partir de la elaboración de un modelo hidrogeológico conceptual

Abstract

The lentic system laguna negra is located in the Boyacá department in jurisdiction of Mongua and Mongui municipalities. Due to the increment of sustainable tourism activities in the region and in addition to the fact that the laguna negra lentic system is provided the municipalities mentioned above and towns surrounding the sector, it is in essential to have knowledge about the hydrogeologic dynamic of the paramo system and specifically the recharge phenomenon in the glacial lagoons in the paramo zones, in order to have a previous knowledge of the hydric processes involved and in this way establish better planning in the conservation of hydric resources. Considering the importance of strategic ecosystems of paramos in Colombia and their special interest in hydric and environmental conservation subjects, the problem to be developed with the specific case study is presented in order to have a knowledge about the hydric recharge behavior of the laguna Negra and its close correlation with the hydrological and hydrogeological dynamics in paramo areas. The laguna negra lentic system being a glacial lagoon located in high mountain zones (paramo), it is a system that may have considerable contributions from both in precipitation and in surface runoff and groundwater flow that recharge it. Likewise, since they are located in paramo areas, these ecosystems are water generators due to specific processes that happens over there. Therefore, for resource planning and prevention of this systems type it is necessary to know technically the hydric contributions, characterize and quantify them in order determinate the availability in terms of hydric supply and that this technical research serves xi as a grounding to take environmental and governmental decisions routed to its conservation and use. The development of this master thesis was supported by the implementation of a conceptual hydrogeological model, in which it the geological characterization of the was performed and the subsequence mapping of geological units in a base integrating geological, stratigraphic and structural information using ArcGis software. This information was supplemented by the application of three spots of the geophysical method (vertical electrical sounding) in the area, to establish the distribution of the geological strata and their possible thickness based on the litophysical correlations, resistivity values and the geological data analyzed. Therefore, it was determinate the existence of lithologic of the lower cretaceous associated to the Une formation (Kiu), Fomeque formation (Kif) and quaternary deposits related to lagoon deposits (Ql) and glacial outburst deposits (Qcg), which are arranged in an eroded anticline type structure that defines the geometry area and the layers disposition. The hydrological model was made from hydro meteorological data associated with multitemporal data series for the nearest station in the study area, and through obtaining the total monthly precipitation parameters and monthly temperature, the hydric balance in the area was carried out using the Thornwaite methodology in which potential evapotranspiration was calculated and parameters corresponding to deficit, reserves and surplus, respectively were determined. The hydraulic parameters of the geological materials were obtained through the relationship of several authors corresponding to porosity, effective porosity, and electric conductivity for the geological lithologies described in the geological model. To establish xii the hydraulic flows behavior integrated into the model, a flow network was created for the area together with its flow lines, establishing the possible flow directions taking into account the topography of the area, hydraulic gradient and the equipotential lines obtained. For the construction of the hydrogeochemical model a hydrochemical analysis was carried out for four samples in which anion and majority cation analyses were performed on possible sources involved in the recharge of the laguna negra lentic system and parameters related to hydrochemical facies and cation exchange processes were determined through the interpretation of hydrochemical diagrams using Diagrammes software. As a complement to the hydrogeochemical model, the analysis of stable isotopes (Oxygen 18 and Deuterium) of four samples was performed to determine the isotopic ratios of the possible sources against a global and local isotopic line to establish the isotopic behavior and trend, and to determine possible origins of the sources according to their isotopic ratios. Eventually mixing models were created based on the relationship of the mass balance equation for two differentiable periods as possible scenarios (rainy season-drainage season) and to determine with the possible sources and the relationship of rainwater origin diagrams, in order to establish the percentage of relationship between each source for the generation of water from the laguna negra lentic system. Finally, the information obtained from the above-mentioned inputs is used to create the conceptual hydrogeological model (HCM) that allows us to know the hydrogeological dynamics of the area, possible water interactions with the environment and the hydrogeological disposition of the characterized units