Un modelo de caja aplicado al trasporte de partículas y tiempo de residencia de las aguas del sector

Abstract

Este estudio se realizó con el fin de aplicar algunos principios de la Oceanografía Física para establecer las posibles causas de la persistencia de condiciones de baja calidad en las aguas del sector ''El Pindo" en la Ensenada de Tumaco y proponer un mecanismo que potencialmente permita el restablecimiento de las condiciones físicas, químicas y biológicas. Se realizaron jornadas de campo tendientes a determinar algunas características hidrológicas (temperatura, salinidad, sólidos suspendidos, oxígeno disuelto, nutrientes y transparencia), batimétricas, hidrodinámicas y meteorológicas del sector motivo de estudio. Los datos obtenidos fueron procesados estadísticamente y algunos de ellos considerados para la elaboración de un modelo de caja y en la consecuente determinación de los tiempos de residencia de estas aguas. Básicamente, durante el período de estudio, se determinó que el sector se caracteriza por presentar bajas profundidades con extensos bancos de arena que en su desarrollo han ocasionado una reducción del canal navegable. La salinidad en marea alta presenta una marcada variación entre la superficie y el fondo, registrando valores entre 21.00 y 33.15o/oo

This study was carried out in order to apply severa! principies of the physical oceanography to determine the possible reasons for persistent law quality water conditions in ''El Pindo" (Tumaco) area and propase a mechanism to recover physical, chemical and biologica/ conditions. The field work was done to determine different hydrological factors (temperature, salinity, suspended solids, dissolved oxygen, nutrients and transparency) as well as bathymetric, hydrodinamic and meteorological characteristics of the selected area. The obtained data were statistically processed and some of them were considered to outline a box model and consequently determine the residence time of these waters. During the period of the study, it was found that shallaw waters with wide sand banks causing the reduced shipway, are predominant. Salinity in high tide presents a remarkable variation between the surf ace and bottom values which were reported to be between 21.00 - 33.15o/oo and 23.22 - 33.22 aloa, respectively. Temperature variations along the water column were registered oscillating between 23.20 - 29.52 ºC and 26.88 - 29.18 ºC in botton and surface, respectively. This area was found to have a particular hydrodinamic circulation pattern, existing an evident difference in the currents course in each tide period due to the involved water volumes. It is concluded that the low water quality of ''El Pindo" area is not due to the circulation pattern but is caused by the bad bottom sediment quality and that could be improved by dredging to clean the waste area. Considering the calculated residence times far these waters (2 - 5 days), it is recommended that control on sawmill activities should be carried out since these are the main source of material deposits in the bottom that affect the water quality and reduce the deep areas causing a negative impact both on the predominant circulation pattem and chemical and biological characteristics of the bottom sediments.