VARIACIÓN ESTACIONAL DE LA CALIDAD DEL AGUA DEL RÍO CACHIL, CON ÉNFASIS EN LA UTILIZACIÓN DEL RECURSO HÍDRICO SUPERFICIAL, SALAMÁ, BAJA VERAPAZ

Abstract

This article has generated information on seasonal variations in water quality of the river that supplies drinking water to the population of Salama, determining the quality indices of the Cachil river that belongs to the watershed of the same name, it is located in the dry corridor in the village of Salama of the department of Baja Verapaz. This paper emphasizes the analysis the variation of water quality from the pollution present in the rainy season calculating the monthly quality indices, through which were identified variations caused by water shortages due to low rainfall and the increased use of water for irrigation in the dry season and increased suspended material from erosion in the rainy season. To determine the variation of water quality there were established four sampling points, one located in the upper part of the watershed (Llano Largo), the second in the middle (El Carmen), the third in the lower (Cachil) and fourth in the catchment area of the treatment plant. Monthly samples were made where in situ parameters were taken and parameters that were analyzed in the laboratory, information that allowed the calculation of water quality indices through WQINSF, which assigns values of importance to each of the variables in which it is based, so that the index can be determined as: (Krendel and Novontny, 1980), where Wi: denotes the importance or weighting factor of the variable (i) with respect to the other variables that make up the index, and weighted between 0 and 1, so that the total is equal to one. Indices used to define the quality variation is mainly due to the levels of electrical conductivity, nitrates, phosphates, dissolved oxygen, total solids, total and fecal coliforms that showed a marked seasonal variation. Cachil river waters generally are classified into quality indices for the rainy season for consumption are between the ranges (40.21 to 60.21) with indices of medium to poor quality, with these characteristics the water could be used with purification treatments. And for agricultural use it is within the same range which could be used for most crops and in some months it has to be treated for irrigation use. It is important to underline that the data could be obtained associating physico-chemical and bacteriological parameters (temperature, dissolved solids, turbidity, phosphates, % oxygen saturation, pH, nitrates, fecal coliform and DBO). It was determined that the morphometry of the watershed is elongated, with a low density of drains that reflects a poorly drained area with a very low hydrological response, with an average slope of 43.21 % and a main channel slope of 5.724 %. Also it was observed that the flow rate decreases considerably from February to April (minimum flow rate is 0. 001 m3 /s at February and at the lower part of the watershed) and August is the maximum flow rate (maximum flow rate 2.33 m3 /s at the El Carmen basin midpoint).