Se ha verificado que la especie invasora lenteja de agua ocupa la mayoría de los espejos de aguas tranquilas en la Bogotá-Región y ha generado repercusiones negativas para los ecosistemas cambiando las dinámicas de las especies. El manejo actual de remover manual o mecánicamente la planta es técnica y económicamente difícil dada la capacidad de la especie de replicarse rápidamente. El presente proyecto de investigación busca aprovechar esa capacidad de replicación para la identificación y caracterización de alternativas de economía circular que permitan el aprovechamiento eficiente de la planta. El trabajo se desarrolló en tres fases, la primera encaminada a validar la problemática en la región, la segunda priorizó las alternativas de aprovechamiento a través de un análisis multicriterio y la tercera desarrolló pruebas de laboratorio para corroborar la factibilidad de las alternativas de aprovechamiento priorizadas en la fase dos. Las alternativas mejor calificadas corresponden al compostaje, bioetanol y biodiesel respectivamente, para las cuales, la producción de bioetanol presentó los mejores resultados en laboratorio. | Ingeniero Ambiental | Pregrado | The aquatic invasive species duckweed reported in the majority of calm water mirrors in the Bogotá-Region has generated effects for the ecosystems, changing the dynamics of the species and habitats, and for the economy in general, since its control is economically unsustainable. The purpose of this research project was to identify and characterize circular economy alternatives for the efficient use of the invasive duckweed species, reducing its environmental impact on the water bodies of Bogotá-Region. During the development of the dimensioning phase, bibliographic references were consulted on studies carried out at the regional, national and international level on the problems faced by the invasive species and the alternative uses that could revolve around it. Once the current situation of duckweed was contextualized, the Multicriteria Analysis methodology was extracted, where different criteria concerning the ecological and economic dimensions of the previously consulted utilization alternatives were evaluated qualitatively and quantitatively; Thus, prioritizing the most viable alternatives will be modified for their subsequent controlled performance in the laboratory. For the composting alternative, there was a time of 21 days, 1.5 kg of duckweed was obtained and the need to complement this procedure with other organic waste and/or insects such as: earthworms or slugs to increase its efficiency was verified. ; on the other hand, the biodiesel generation alternative arises from low efficiency with a product of 11,456 ml from the extraction of the essential oil of 30 ml of duckweed and 7 ml of methoxide; Finally, the bioethanol generation alternative showed great efficiency in the distillation procedure with a 48 ml product from 100 ml of fermented duckweed solution.

[Introduction]: Georeferenced environmental information from environmental institutions is the basis for improving environmental management and sustainability in the Latin American and Caribbean region. [Objective]: To evaluate the spatio-temporal evolution of the water table using groundwater level data measured in the network of monitoring wells of the Sébaco Valley aquifer. [Methodology]: The fluctuation of groundwater levels was evaluated during the dry seasons from 2010 to 2018 (9 years) based on water level measurements collected from the network of monitoring wells of the Sébaco Valley aquifer. The geostatistical approach applied to this dataset to reveal the predictive models was the Empirical Bayesian Kriging (EBK) method. This method obtained a spatial representation of the phreatic surface of the aquifer and was subsequently used to calculate the velocity and acceleration of the water table. [Results]: During the period analyzed, water table acceleration maps showed mean values of -0.52 m/year. These values suggest that part of the aquifer is experiencing a decline in water table levels that could be rapidly aggravated by climatic events and increased demand of water resources. [Conclusions]: The approach used for quantitative assessment of groundwater levels is suitable for countries lacking a database of aquifer-specific hydraulic parameters. | [Introducción]: La información ambiental georreferenciada que provienen de instituciones ambientales constituye información base, para mejorar la gestión ambiental y de sostenibilidad en la región de América Latina y El Caribe. [Objetivo]: Evaluar la evolución espacio-temporal del nivel freático utilizando datos de niveles de agua subterránea medidos en la red de pozos de monitoreo del acuífero Valle de Sébaco. [Metodología]: Se evaluó durante la época seca del 2010 al 2018 (9 años) la fluctuación de los niveles de agua subterránea, a partir de datos de niveles de agua medidos en la red de pozos de monitoreo del acuífero Valle de Sébaco. El enfoque geoestadístico que se empleó en este conjunto de datos, para revelar los modelos predictivos fue el método Kriging Empírico Bayesiano (EBK), dicho método obtuvo una representación espacial de la superficie freática del acuífero y posteriormente fue utilizado para calcular la velocidad y aceleración del nivel freático. [Resultados]: Durante el período analizado los mapas de aceleración del nivel freático mostraron valores medios de -0.52 m/año. Estos valores sugieren que una parte del acuífero está experimentando un descenso en los niveles freáticos que podría verse agravado rápidamente con los fenómenos climáticos y el aumento de la demanda del recurso. [Conclusiones]: El enfoque utilizado para la evaluación cuantitativa de los niveles de agua subterránea es adecuado para países que carecen de base de datos de parámetros hidráulicos específicos de un acuífero. | [Introdução]: As informações ambientais georreferenciadas provenientes de instituições ambientais constituem informações básicas para melhorar a gestão ambiental e de sustentabilidade na região da América Latina e Caribe. [Objetivo]: Avaliar a evolução espaço-temporal do lençol freático utilizando dados de nível freático medidos na rede de poços de monitoramento do aquífero Vale do Sébaco. [Metodologia]: A flutuação dos níveis de água subterrânea foi avaliada durante a estação seca de 2010 a 2018 (9 anos), com base em dados de níveis de água medidos na rede de poços de monitoramento do aquífero do Vale do Sébaco. A abordagem geoestatística utilizada neste conjunto de dados para revelar os modelos preditivos foi o método Empirical Bayesian Kriging (EBK), este método obtém uma representação espacial da superfície do lençol freático do aquífero e foi posteriormente utilizado para calcular a velocidade e aceleração do lençol freático. [Resultados]: Durante o período analisado, os mapas de aceleração do nível freático apresentaram valores médios de -0,52 m/ano. Esses valores sugerem que parte do aquífero está passando por uma queda no nível do lençol freático que pode ser rapidamente agravada por eventos climáticos e aumento da demanda pelo recurso. [Conclusões]: A abordagem utilizada para a avaliação quantitativa dos níveis de água subterrânea é adequada para países que não possuem um banco de dados de parâmetros hidráulicos específicos para um aquífero.

The creation of artificial dunes for coastal protection may have important consequences for freshwater lenses in coastal aquifers. The objective of this study was to compare the recharge processes below such a young dune with scant vegetation to an older dune covered by grass and herbaceous vegetation. To this aim, soil and water samples were collected from the unsaturated zone at two sites on Langeoog Island in northern Germany, and the soil water was analysed for stable water isotopes and chloride. Recharge rates were calculated by using a new version of HYDRUS-1D, which was modified to simulate isotope fractionation during evaporation. Both the model outcomes and the data highlight the importance of fractionation, which is slightly more pronounced at the older, more vegetated dune. At the newly constructed dune, vegetation dieback seemingly reduces the importance of transpiration during summer. Recharge occurs year-round, albeit predominantly during the winter months. Calculated recharge rates are consistent with lysimeter measurements, but are significantly higher than previously reported rates based on groundwater age data, which is primarily attributed to the absence of dune shrub at the sites investigated here. More data are needed to establish the importance of soil-water repellency and overland flow. Based on the results, it is proposed that repeated isotope sampling can yield important insights into the dynamics of recharge processes, including their response to climate change.

River impoundment is an alternative to artificial groundwater recharge in coastal aquifers, while mitigating seawater intrusion caused by anthropogenic activities. This study implements a new multiobjective optimization framework for management of the existing engineering measures of river multidamming impoundment and strategies for groundwater abstraction in Dagu River Basin, a water-scarce basin in north China. The optimization framework integrates a calibrated numerical model with a conceptualized river package to simulate the interaction between the Dagu River and groundwater due to river impoundment, and it focuses on the tradeoff among minimizing the seawater intrusion extent, minimizing the river seepage, and maximizing the allowable groundwater abstraction. Then the elitist nondominated sorting genetic algorithm (NSGA-II) is used to search for the Pareto-optimal solutions affected by different climate conditions. Results show that the river water level and groundwater abstraction schemes can be regulated to achieve the optimal tradeoffs among different objectives. To mitigate seawater intrusion, the impoundment river water level behind the dam adjacent to the seawater intrusion associated with years of insufficient precipitation should be raised by at least 0.5–1.5 m, while the river level behind the remaining dams should be reduced by at least 1 m. Moreover, under the constraint of restricting groundwater abstraction, the annual groundwater abstraction in the four county-level administrative subdomains should be adjusted by 1.2–1.5 million m³ or more in years with less precipitation compared to that in years with more precipitation. The implications might also be applied to other coastal aquifers with intense human activities.

La tecnología del internet de las cosas (IoT) a través de los años ha tenido una constante evolución empezando primero con el envío de información básica para posteriormente ser empleada en la mayoría de campos partiendo desde lo más básico como prender un televisor hasta lo más complejo como el monitoreo en tiempo real de las condiciones climáticas, del suelo y obtención de información de los cultivos para que haya una producción más eficiente en la agricultura. Para el presente proyecto se empleó la tecnología IoT a través de sensores de bajo costo. Estos primeramente fueron instalados en la reserva hídrica de Paluguillo donde se tomaron mediciones de distintas variables meteorológicas. Posterior a esto estas mismas variables fueron analizadas para dos cultivos de ciclo corto en un terreno ubicado en la parroquia de Conocoto, donde se calculó el balance hídrico para una optimización del riego partiendo de datos como la evapotranspiración (ETc). La cual fue calculada mediante el método del tanque evaporímetro Clase A empleando el sensor de nivel del agua. Para la distribución de los cultivos, el terreno fue dividido en dos secciones una con riego controlado por medio de los valores obtenidos del balance hídrico y de los sensores. Y la otra sección con un riego no controlado para evidenciar si se da un desarrollo eficiente de los cultivos sin emplear la tecnología IoT. Mediante los resultados obtenidos se estima que el desarrollo de los cultivos es eficiente mediante un monitoreo constante de las variables climáticas de la zona. | The Internet of Things (IoT) technology over the years has had a constant evolution, starting first with the sending of basic information to later be used in most fields, starting from the most basic such as turning on a television to the most complex. such as real-time monitoring of climatic and soil conditions and obtaining information on crops so that there is more efficient production in agriculture. For this project, IoT technology was used with low-cost sensors. These were first installed in the Paluguillo water reserve where measurements of different meteorological variables were taken. After this, these same variables were analyzed for two short-cycle crops in a plot of land located in the parish of Conocoto, where the water balance was calculated for irrigation optimization based on data such as evapotranspiration (ETc). Which was calculated using the Class A evaporimeter tank method using the water level sensor. For the distribution of the crops, the land was divided into two sections, one with irrigation controlled by means of the values obtained from the water balance and from the sensors. And the other section with uncontrolled irrigation to show if there is an efficient development of crops without using IoT technology. Through the results obtained, it is estimated that the development of crops is efficient through constant monitoring of the climatic variables of the area. | Manciati Jaramillo, Carla Paola, director.

Faults may impact regional groundwater flow and transport, so it is important to include them during aquifer-system conceptualization and while constructing groundwater flow models. For the Neogene aquifer in Flanders (Belgium), three-dimensional groundwater-flow and solute-transport models have been developed in the framework of safety and feasibility studies for the underlying Boom Clay Formation as a potential host for geological disposal of radioactive waste. The model outcomes are subject to uncertainties as they are typically constrained only by hydraulic heads, and their current conceptualization does not differentiate the fault zones from the undisturbed hydrostratigraphic formations. A groundwater flow model has been developed using MODFLOW-2005 to investigate how groundwater flow in the sedimentary Neogene aquifer may be disturbed by the Rauw Fault—a 55-km-long normal fault—across the Nete catchment. The observed hydraulic gradient across the fault zone appears significant, with head differences of 1.5–2.0 m over a horizontal distance of 60 m. A simulated hydraulic-head difference of 2.4 m was achieved largely corresponding to the observed behavior. The Neogene aquifer, within the Nete catchment, seems to be composed of several local flow systems and potentially with a deeper more semiregional/intermediate flow system. Testing different fault configurations shows the impact on the local/semiregional flow system, with pronounced effects in the fault’s vicinity, and extending or narrowing the flow systems further away. These results demonstrate the importance of considering faults, or any other hydrogeological subsurface barrier/conduit, and suggests they should be accounted for in the general practice of subsurface activity impact assessment.

Groundwater recharge (GR) is a complex process that is difficult to quantify. Increasing attention has been given to unsaturated zone modeling to estimate GR and better understand the processes controlling it. Continuous soil-moisture time series have been shown to provide valuable information in this regard. The objectives of this study were to (i) analyze the processes and factors controlling GR in an unconfined granular aquifer in a cold and humid environment and (ii) assess the uncertainties associated with the use of data from different sources. Soil moisture data monitored over three years at three experimental sites in southern Quebec (Canada) were used to calibrate the HYDRUS-1D model and to estimate ranges of possible GR in a region where groundwater is increasingly used as a source of fresh water. The simulations identified and quantified important factors responsible for the near-surface water balance that leads to GR. The resulting GR estimates from 2016 to 2018 showed marked differences between the three sites, with values ranging from 347 to 735 mm/y. Mean GR for the three sites was 517 mm/y for 2016–2018 and 455 mm/y for the previous 12-year period. GR was shown to depend on monthly variations in precipitation and on soil textural parameters in the root zone, both controlling soil-water retention and evapotranspiration. Monthly recharge patterns showed distinct preferential GR periods during the spring snowmelt (38–45% of precipitation) and in the fall (29% of precipitation). The use of different meteorological datasets was shown to influence the GR estimates.

Groundwater pollution source identification (GPSI) provides information about the temporal and spatial distribution of pollution sources and helps decision makers design pollution remediation plans to protect the groundwater environment. The Bayesian approach based on the Markov Chain Monte Carlo (MCMC) approach provides an efficient framework for GPSI. However, MCMC sampling entails multiple model calls to converge to the posterior probability distribution of unknown pollution source parameters and entails a massive computational load if the simulation model is directly called. This study aimed to develop an innovative framework in which an improved MCMC approach was linked to a surrogate model. Sensitivity analysis was incorporated into the MH-MCMC approach, named SAMH-MCMC (sensitivity analysis based Metropolis Hastings-Markov Chain Monte Carlo), to speed up the convergence of the posterior distribution in a novel way to control the search step size. Three computationally inexpensive surrogate models for the simulation model were proposed: support vector regression, Kriging (KRG), and multilayer perceptron, and the most accurate model was chosen. The feasibility and advantages of the developed framework were evaluated and validated through two hypothetical numerical cases with homogenous and heterogeneous media. The proposed approach has strong convergence robustness as it considers the sensitivities of the unknown parameters that characterise groundwater pollution sources and can achieve high identification accuracy. Furthermore, the KRG surrogate model has a higher accuracy than other surrogate models, owing to its linear unbiased estimation characteristic. Overall, the framework developed in this study is a promising solution for identifying groundwater pollution source parameters.

Large-scale studies of the spatial and temporal variation of groundwater drought status require complete inventories of groundwater levels on regular time steps from many sites so that a standardised drought index can be calculated for each site. However, groundwater levels are often measured sporadically, and inventories include missing or erroneous data. A flexible and efficient modelling framework is developed to fill gaps and regularise data in such inventories. It uses linear mixed models to account for seasonal variation, long-term trends and responses to precipitation and temperature over different temporal scales. The only data required to estimate the models are the groundwater level measurements and freely available gridded weather products. The contribution of each of the four types of trends at a site can be determined and thus the causes of temporal variation of groundwater levels can be interpreted. Validation reveals that the models explain a substantial proportion of groundwater level variation and that the uncertainty of the predictions is accurately quantified. The computation for each site takes less than 130 s and requires little supervision. Hence, the approach is suitable to be upscaled to represent the variation of groundwater levels in large datasets consisting of thousands of boreholes.

Enhanced bioremediation combined with in-situ chemical oxidation has the potential to remediate groundwater contaminated with organics. To explore the remediating effects of these two approaches and to evaluate their combined feasibility, traditional gasoline (no ethanol) and ethanol-gasoline (10% ethanol, v/v) were released into experimental sand tanks (TG-tank and EG-tank, respectively) under the same water-flow conditions. Nitrate and sulfate were added to enhance bioremediation and then persulfate was injected to encourage chemical oxidation. Two push–pull tests, using persulfate and bromide respectively, were conducted to compare their behavior. The results showed that nitrate reduction, rather than sulfate reduction, enhanced BTEX (benzene, toluene, ethylbenzene, and xylene) biodegradation, but the presence of ethanol inhibited these processes. The detected concentration of BTEX in the TG-tank was lower than that in the EG-tank, and the first-order decay rate constants of BTEX in the TG-tank and EG-tank under nitrate-adjusted conditions were 0.0058 and 0.0016 d⁻¹, respectively. The first persulfate injection (10 g L⁻¹) resulted in 86 and 94% concentration decreases of BTEX in the TG-tank and EG-tank, respectively, at first-order decay rates of 0.0180 and 0.0181 d⁻¹, respectively. However, the subsequent persulfate injections at 20 and 50 g L⁻¹ had no significant removal effect on BTEX. Persulfate oxidation made pH decrease (but it quickly recovered) and did not significantly inhibit nitrate reduction. This study suggests that enhanced nitrate reduction can be combined with persulfate oxidation for the in-situ remediation of groundwater contaminated by petroleum hydrocarbons.