Desarrollo de índices para evaluar la calidad del agua de ríos de la vertiente del Pacífico de Guatemala
Fecha
2024
Autores
Gil Rodas de Castillo, Norma Edith
Título de la revista
ISSN de la revista
Título del volumen
Editor
Universidad Nacional (Costa Rica)
Resumen
Resumen. Guatemala, posee una población de 17.6 millones de habitantes, de los cuales el 46.2 % residen en la costa sur, denominada como la vertiente del Pacífico. Esta región alberga 18 de los 35 ríos principales. El 68 % de la actividad agrícola en esta zona se basa en monocultivos, como la caña de azúcar y la palma africana. Estos procesos consumen el 77 % de los recursos hídricos disponibles para riego y otras actividades. Siendo devueltos frecuentemente con altos niveles de contaminación, incluyendo fertilizantes e insecticidas. Lo anterior provoca escasez de agua de calidad para las comunidades que habitan en estas áreas. Desafortunadamente, en Guatemala no existe un reglamento específico para evaluar las propiedades físicas, químicas y biológicas de los ríos. Para abordar esta carencia, se llevó a cabo una búsqueda de regulaciones utilizadas en otros países y estas sirvieron de base para escribir una “Normativa propuesta para evaluar la Calidad del Agua de los ríos de Guatemala”. En los años 2018 y 2019, se realizaron muestreos de indicadores de calidad fisicoquímica, microbiológica y biológica del agua en diversos ecosistemas lóticos de la vertiente del Pacífico de Guatemala. También se utilizó el Protocolo de Bioevaluación Rápida (RBP) como índice de control debido a la confiabilidad que presenta el mismo. Durante el 2018, se llevaron a cabo muestreos en seis ríos de la vertiente del Pacífico, siendo estos: Acomé, María Linda, Los Esclavos, Madre Vieja, Sis Ican y Ocosito. Los resultados fueron evaluados con el Índice de Calidad del Agua propuesto por Calvo-Brenes (2019), conocido como ICA-Calvo-TEC. Este índice que utiliza la normativa costarricense, se empleó con el fin de hacer un análisis preliminar de la calidad del agua. Se encontró que la mayoría mostraban niveles de calidad desde la clase 3, 4 y 5, indicando contaminación “moderada”, “severa” y “muy severa” respectivamente. Estos resultados preliminares del año 2018 mostraron poca variabilidad en los niveles de calidad entre los diferentes puntos de muestreo. Para desarrollar un índice, resulto conveniente tener más variables de calidad, partiendo de aguas no contaminadas hasta altamente contaminadas. Es así que para el año 2019 se definieron 10 localidades solamente en tres ríos, siendo estos: Acomé, Los Esclavos y María Linda. En cada uno se eligieron tres lugares, excepto en el Río María Linda, donde se seleccionaron cuatro, debido a las diferencias ambientales y geomorfológicas que afectaban la calidad del agua de los ríos. El análisis de los indicadores de calidad en función del tiempo, sugiere una correlación entre estos y la cantidad de lluvias en cada mes. La excepción a esta relación se dio con la salinidad, conductividad, sólidos disueltos totales, coliformes totales, fecales, y el Protocolo de Bioevaluación Rápida (RBP). En cuanto a los macroinvertebrados acuáticos el 90 % de los sitios de muestreo presentaron una alta diversidad de especies, principalmente en las partes altas de los ríos. En las áreas bajas, se encontró menor diversidad y alta dominancia. De todos los taxones identificados el orden Decapoda presentó el 74.74 %, la clase Insecta el 15.95 % y Gastropoda el 9.09 %. En la clase Insecta los órdenes que presentaron mayor abundancia fueron Hemiptera con un 34.54 % y Ephemeroptera con un 25.02 %. Por la diversidad de especies se considera que el agua de los ríos de la vertiente del Pacífico no está totalmente deteriorada. Con los resultados anteriores y con la Normativa propuesta para evaluar la calidad del agua de los ríos de Guatemala se desarrollaron dos índices: uno fisicoquímico de calidad del agua nombrado como ICA-GT y otro biológico nombrado Biological Monitoring Working Partiy BMWP-GT (por sus siglas en inglés), para uso en toda la república. La evaluación de la calidad del agua utilizando el ICA-GT mostró lo siguiente: el 1.7 % sin contaminación, el 23.3% incipiente, el 43.3 % moderada, el 30 % severa y el 1.7 % contaminación muy severa. Para el BMWP-GT, se propusieron dos índices: BMWP-GT1 y BMWP-GT2, los cuales clasificaron de manera similar los resultados de los muestreos del año 2019 en los tres ríos: 0 % excelente, 3.3 % buena, 13.3 % regular, 46.7 % mala y 36.7 % pésima. Aunque el ICA-GT y el BMWP-GT representaron una correlación elevada, no siempre clasificaron la calidad del agua de la misma manera en términos de color y niveles de clasificación. Esto es debido a las diferencias en las metodologías empleadas y las escalas de clasificación, así como la discrepancia en indicadores de calidad empleados para cada uno de ellos. Es necesario continuar realizando estudios de calidad física, química y biológica, abarcando más ríos y áreas que no estén alteradas por la actividad humana, para seguir avanzando en este tema.
Abstract. 46.2% of Guatemala´s estimated population of 17 million people reside on the southern coast, which comprises the Pacific basin. This region includes 18 of Guatemala´s 35 largest rivers. 68 % of agricultural activity in this area relies on monocultures, such as sugarcane and African palm. These crops use up to 59 % of the water resources available for irrigation and other activities. Post irrigation water is often returned to the rivers with high levels of pollution, including fertilizers and pesticides. This leads to scarcity of good quality water for the communities living in that area. Unfortunately, in Guatemala there are no specific regulations to assess the chemical, physical, and biological qualities of rivers. To address this deficiency, a search for water quality regulations used in other countries was conducted. Those regulations became the basis for the proposed “Normativa propuesta para evaluar la calidad del agua de los ríos de Guatemala” (proposed norm to regulate the assessment of water quality in Guatemala´s rivers). Samples were collected in 2018 and 2019 to determine the physical, chemical, microbiological, and biological water quality conditions in different lotic ecosystems in the Pacific water basin in Guatemala. In addition, the Rapid Bioassessment Protocol (RBP) was used as a control index due to its reliability and that it does not change with the effects of different climatic seasons. In 2018, sampling was conducted in six rivers: Acomé, María Linda, Los Esclavos, Madre Vieja, Sis Ican, and Ocosito. Results were analyzed using the Water Quality Index proposed by Calvo-Brenes (2019), known as ICA-Calvo-TEC. This index uses Costa Rican regulations in order to make a preliminary analysis of water quality. It was found that most showed quality levels from class 3, 4 and 5, indicating "moderate", "severe" and "very severe" contamination respectively. These preliminary results from 2018 show little variability in quality levels between the different sampling points. To develop an index, it is desirable to have greater variabilities in quality, starting from unpolluted to highly polluted waters. Thus, for the year 2019, 10 localities were defined in three rivers alone, these being: Acomé, Los Esclavos and María Linda. In each one, three sites were chosen, except in the María Linda River, where four were selected, due to the environmental and geomorphological differences that affected the water quality of the rivers. The analysis of the quality indicators as a function of time suggests a correlation between them and the amount of rainfall in each month. The exception to this relationship was salinity, conductivity, total dissolved solids, total coliforms, fecal coliforms, and the Rapid Bioassessment Protocol (RBP). The aquatic macroinvertebrates showed high species diversity in 90% of the sampling sites, mostly near headwaters. Downstream less diversity and more dominance were observed. From all identified taxa, Decapoda were dominant (74.74%), followed by Insecta (15.95%) and Gastropoda (9.9%). Within Insecta Hemiptera (34.54%) and Ephemeroptera (25.02%) were more abundant. These results show that the water quality of the Pacific basin rivers in Guatemala is not totally deteriorated. With the above results and with the proposed Regulations to evaluate the water quality of the rivers of Guatemala, two indices were developed: Named ICA-GT and another biological named Biological Monitoring Working Party BMWP-GT, for use throughout the republic. The assessment of water quality using ICA-GT yielded the following results: 1.7 % with no pollution, 23.3 % incipient, 43.3 % moderate, 30 % severe, and 1.7 % very severe pollution. For BMWP-GT, two indices were proposed, BMWP-GT-1 and BMSP-GT-2, which classified the results of the 2019 sampling in the three rivers similarly. The results of water quality with both biological indices were classified as follows: 0 % excellent, 3.3 % good, 13.3 % fair, 46.7 % poor, and 36.7 % very poor. Although the ICA-GT and BMWP-GT represented a high correlation, they did not always rank water quality in the same way in terms of color and rating levels. Due to the differences in the methodologies used and the classification scales, as well as the discrepancy in quality indicators used for each of them. To further enhance the understanding of water quality in Guatemala, it is necessary to continue conducting studies on physical, chemical, and biological quality, covering more rivers and areas unaffected by human activity. This will allow for comparisons between pristine locations and more degraded sites, and provide ground for recommendations for river improvement.
Abstract. 46.2% of Guatemala´s estimated population of 17 million people reside on the southern coast, which comprises the Pacific basin. This region includes 18 of Guatemala´s 35 largest rivers. 68 % of agricultural activity in this area relies on monocultures, such as sugarcane and African palm. These crops use up to 59 % of the water resources available for irrigation and other activities. Post irrigation water is often returned to the rivers with high levels of pollution, including fertilizers and pesticides. This leads to scarcity of good quality water for the communities living in that area. Unfortunately, in Guatemala there are no specific regulations to assess the chemical, physical, and biological qualities of rivers. To address this deficiency, a search for water quality regulations used in other countries was conducted. Those regulations became the basis for the proposed “Normativa propuesta para evaluar la calidad del agua de los ríos de Guatemala” (proposed norm to regulate the assessment of water quality in Guatemala´s rivers). Samples were collected in 2018 and 2019 to determine the physical, chemical, microbiological, and biological water quality conditions in different lotic ecosystems in the Pacific water basin in Guatemala. In addition, the Rapid Bioassessment Protocol (RBP) was used as a control index due to its reliability and that it does not change with the effects of different climatic seasons. In 2018, sampling was conducted in six rivers: Acomé, María Linda, Los Esclavos, Madre Vieja, Sis Ican, and Ocosito. Results were analyzed using the Water Quality Index proposed by Calvo-Brenes (2019), known as ICA-Calvo-TEC. This index uses Costa Rican regulations in order to make a preliminary analysis of water quality. It was found that most showed quality levels from class 3, 4 and 5, indicating "moderate", "severe" and "very severe" contamination respectively. These preliminary results from 2018 show little variability in quality levels between the different sampling points. To develop an index, it is desirable to have greater variabilities in quality, starting from unpolluted to highly polluted waters. Thus, for the year 2019, 10 localities were defined in three rivers alone, these being: Acomé, Los Esclavos and María Linda. In each one, three sites were chosen, except in the María Linda River, where four were selected, due to the environmental and geomorphological differences that affected the water quality of the rivers. The analysis of the quality indicators as a function of time suggests a correlation between them and the amount of rainfall in each month. The exception to this relationship was salinity, conductivity, total dissolved solids, total coliforms, fecal coliforms, and the Rapid Bioassessment Protocol (RBP). The aquatic macroinvertebrates showed high species diversity in 90% of the sampling sites, mostly near headwaters. Downstream less diversity and more dominance were observed. From all identified taxa, Decapoda were dominant (74.74%), followed by Insecta (15.95%) and Gastropoda (9.9%). Within Insecta Hemiptera (34.54%) and Ephemeroptera (25.02%) were more abundant. These results show that the water quality of the Pacific basin rivers in Guatemala is not totally deteriorated. With the above results and with the proposed Regulations to evaluate the water quality of the rivers of Guatemala, two indices were developed: Named ICA-GT and another biological named Biological Monitoring Working Party BMWP-GT, for use throughout the republic. The assessment of water quality using ICA-GT yielded the following results: 1.7 % with no pollution, 23.3 % incipient, 43.3 % moderate, 30 % severe, and 1.7 % very severe pollution. For BMWP-GT, two indices were proposed, BMWP-GT-1 and BMSP-GT-2, which classified the results of the 2019 sampling in the three rivers similarly. The results of water quality with both biological indices were classified as follows: 0 % excellent, 3.3 % good, 13.3 % fair, 46.7 % poor, and 36.7 % very poor. Although the ICA-GT and BMWP-GT represented a high correlation, they did not always rank water quality in the same way in terms of color and rating levels. Due to the differences in the methodologies used and the classification scales, as well as the discrepancy in quality indicators used for each of them. To further enhance the understanding of water quality in Guatemala, it is necessary to continue conducting studies on physical, chemical, and biological quality, covering more rivers and areas unaffected by human activity. This will allow for comparisons between pristine locations and more degraded sites, and provide ground for recommendations for river improvement.
Descripción
Gil Rodas de Castillo, N. E. (2024). Desarrollo de índices para evaluar la calidad del agua de ríos de la vertiente del Pacífico de Guatemala. [Tesis de Doctorado] Universidad Nacional, Heredia, Costa Rica.
Palabras clave
CALIDAD DEL AGUA, RÍOS, GUATEMALA, INVERTEBRADOS, CONTAMINACIÓN DEL AGUA, INDICADORES AMBIENTALES, WATER QUALITY, RIVERS, ORGANISMOS ACUÁTICOS, AQUATIC ORGANISMS