Franklin Torres-Bejarano

Effects of beach tourists on bathing water and sand quality at Puerto Velero, Colombia

Fragile coastal areas suffer from human activities. Environmental quality is one of the most important aspects in a tourist destination of sun and sand. The quality of bathing water and sand became indicators in the worldwide competition of beach destinations. We studied the water and sand quality along the beach of Puerto Velero, in northern Colombia. Water and sand beach quality were monitored during thirteen months. This allowed identifying the most significant sources of pollution along the beach, and understanding the interrelationship between tourism and the effects on the environment. Linear correlations allow assessing the association between the number of visitors and the physicochemical and microbiological parameters. The number of visitors was directly correlated with the presence of grease and oils, both in water and sand, as well as with fecal coliforms in water. A relation between the suspended solids and the presence of fecal coliforms in water and sand was observed. This statistical approach allows understanding the origin of beach sand and swimming water pollution at tourist beaches. Overall, sand quality has an important influence and is directly related to the water quality of the beach. Both the number of tourists and their activities are main factors explaining the contamination of the water and sand. This shows the importance of management of waste and wastewater in combination with awareness raising initiatives. More research should include monitoring and evaluating of both water and sand beach and provide data to revise the existing legal framework.

A Study Case of Hydrodynamics and Water Quality Modelling: Coatzacoalcos River, Mexico

The common basis of the modeling activities is the numerical solution of the momentum and mass conservation equations in a fluid. For hydrodynamic modeling, the Navier-Stokes equations are usually simplified according to the specific water body properties, obtaining, for example, the shallow water equations, so called because the horizontal scale is much larger than the vertical. Therefore, in cases where the river has a relation width-depth of 20 or more and for many common applications, variations in the vertical velocity are much less important than the transverse and longitudinal direction (Gordon et al., 2004). In this sense, the equations can be averaged to obtain the vertical approach in two dimensions in the horizontal plane, which adequately describes the flow field for most of the rivers with these characteristics. At the same time, the contaminant transport models have evolved from simple analytical equations based on idealized reactors to sophisticated numerical codes to study complex multidimensional systems. Since the introduction of the classic Streeter-Phelps model in the 1920 to evaluate the Biochemical Oxygen Demand and dissolved oxygen in a steady state current, contaminant transport and water quality models have been developed to characterize and assist the analysis of a large number of water quality problems. This chapter presents the numerical solution of the two-dimensional Saint-Venant and Advection-Diffusion-Reaction equations to calculate the free surface flow and contaminant transport, respectively. The solution of both equations is based on a second order EulerianLagrangian method. The advective terms are solved using the Lagrangian scheme, while the Eulerian scheme is used for diffusive terms. The specific application to the Coatzacoalcos River, Mexico is discussed, having as a main building block the water quality assessment supported on mathematical modelling of hydrodynamics and contaminants transport. The solution method here proposed for the two-dimensional equations, yields appropriate results representing the river hydrodynamics and contaminant behaviour and distribution when comparing whit field measurements. In this work is presented the structure of a numerical model giving an overview of the program scope, the conceptual design and the structure for each hydrodynamic, pollutants transport and water quality modules that includes ANAITE/2D model (Torres-Bejarano and Ramirez, 2007). The numerical solution scheme is detailed explained for both Saint-Venant and the Advection-Diffusion-Reaction equation. To validate the model, some comparisons were made between model results and different field measurements.

Contamination Level and Spatial Distribution of Heavy Metals in Water and Sediments of El Guájaro Reservoir, Colombia

Heavy metals have become a subject of special concern worldwide, mainly due to high persistence in the environment, toxicity, biogeochemical recycling and ecological risk. Therefore, the objective of this investigation was to analyze the spatial–temporal distribution of heavy metals in water and sediments to determine the environmental status of El Guájaro Reservoir, where such studies have not been developed. Two measurement campaigns (dry and wet period) were carried out and eight sampling stations were selected. A comparison of water and sediment quality parameters with existing national and international regulations was done. Also, heavy metal distribution maps were generated, and the geoaccumulation index was calculated to identify sources and sediments contamination level. Based on the obtained results, agriculture and mining activities are the main causes of the reservoir contamination. This metals levels could be a potential risk for the aquatic life and the populations that are supplied from this water body.

Light Particle Tracking Model for Simulating Bed Sediment Transport Load in River Areas

In this work a fast computational particles tracer model is developed based on Particle-In-Cell method to estimate the sediment transport in the access zone of a river port area. To apply the particles tracer method, first it is necessary to calculate the hydrodynamic fields of the study zone to determine the velocity fields in the three directions. The particle transport is governed mainly by the velocity fields and the turbulent dispersion. The mechanisms of dispersion and resuspension of particles are based in stochastic models, which describes the movement through a probability function. The developed code was validated using two well known cases with a discrete transformation obtaining a max relative error around 4.8% in both cases. The simulations were carried out with 350,000 particles allowing us to determine under certain circumstances different hydrodynamic scenarios where the zones are susceptible to present erosion and siltation at the entrance of the port.

Numerical Modeling of Hydrodynamics in the Agua Brava Lagoon, Located in Nayarit, Mexico

In this paper a study of the hydrodynamics of the Agua Brava lagoon system is performed by numerical modeling. The importance of studying this lagoon system lies with aquaculture activities carried out by shrimp farms. The \( \pi \)-HYDRO model is used for the numerical simulations of hydrodynamics and temperature and salinity dispersion. The boundary conditions regarding ocean properties were generated with the HYCOM ocean model, whereas tides were calculated from the tidal predictions of the MAR V1.0. A hydrological study was also performed to calculate the freshwater contributions and take them into account in the numerical simulations. The scenarios analyzed are the dry and wet seasons particularly for 2013. For the case of the dry season, a slight influence of hydrological contributions to the dynamics of the lagoon is observed, where the effects of the tidal flow are predominant. For the wet scenario, the effects of both tidal and hydrological flow drive the motion within the lagoon, especially being predominant the hydrological flow due to the river discharges in the near region to the shrimp farms.

Numerical Modelling of the Laguna Verde Nuclear Power Station Thermal Plume Discharge to the Sea

The coastal water pollution is a problem that responds to the overpopulation, natural resources exploitation and the increase of technologic development; this has led to an alteration of the physical, chemical and biological parameters of both continental and coastal waters. Among the main sources of pollution are those arising from industrial activities, this is the case of the electricity generation industry which requires large volumes of water for cooling systems. This work contributes to the knowledge of the behaviour of thermal discharges into coastal waters, and it requires solving the Navier-Stokes-Reynolds equations for shallow waters, using a numerical model formerly developed; water quality equations associated are solved too. The results obtained are satisfactory, since dispersion patterns of the thermal plume are well reproduced in accordance with the patterns measured for different climate scenarios in the zone.

Hydraulic and Environmental Design of a Constructed Wetland as a Treatment for Shrimp Aquaculture Effluents

Shrimp aquaculture has grown to the extent that pressure on natural ecosystems has greatly increased. The shrimp farms effluents usually discharge their wastes, with high nutrients load, into coastal water bodies without any previous treatment. This work presents a method to design a constructed wetland for handling these effluents. Our method is based on a first order equation model and a hydrodynamic numerical model as the main component for the design process. Numerical results showed consistency with the first order theory, when pollutants concentration were reduced to values accepted by the applicable regulations.

Hydrodynamics modelling utilizing the EFDC Explorer model for the sustainable management of Canal del Dique-Guajaro hydrosystem, Colombia

Guajaro reservoir is located in the south east of Atlantico department (Colombia). This water body is the most important in the region since its construction in 1964. It is supplied by an artificial channel (Canal del Dique) by means of a two floodgate system. As a result of excess nutrients and other pollution loads from the drainage basin in recent decades, Guajaro reservoir has suffered eutrophication and other pollution problems, however it still continues to be exploited. For this reason, it is necessary to regulate the hydraulic structures that supply this water body, as they play an important role in managing levels and these in turn for the purpose of water supply and environmental purposes. The present work has been carried out as a sustainability management alternative of the reservoir. The implementation of a two-dimensional hydrodynamic model (EFDC Explorer) and its calibration is implemented using a time series of the free surface levels, and comparing the measured velocities and those estimated by the model for two different climatic periods, to assist the operation of Hydrosystem Canal del DiqueGuajaro. The corresponding comparisons showed a good behaviour between measured and simulated data. Based on the quantitative results of the NashSutcliffe reliability method, it is considered that the results are quite satisfactory to estimate and predict the amount of water flowing in and out of the reservoir through the hydrosystem channel reservoir.