Evaluation of two water quality indices in several sites of the La Central stream, Pacayas de Alvarado, Costa Rica

Abstract

La Central Stream located in San Martín de Irazú is the current that supplies water for human consumption, to three communities of the Pacayas district of Alvarado de Cartago. The stream is currently surrounded by an environment in which intensive agricultural and livestock-type activities prevail, and with a low percentage of forest resources. In addition, the land has a slope that favors the occurrence of runoff to the ravine in rainy weather. All these factors negatively affect the quality of the nascent. The objective of the research was to evaluate the quality of the water in several places of the creek: the nascent, the creek downstream, the catchment tank and the creek upstream. The evaluation was carried out by means of two water quality indexes (ICAs): the Dutch one and the one proposed by Calvo-Brenes, which considers environmental aspects and the Costa Rican regulations. The Dutch index requires the analysis of three chemical physical quality indicators, while the second evaluates seven physicochemical and microbiological indicators. It was found that the Dutch index underestimates water quality compared to the new index proposed by Calvo-Brenes. This difference is mainly due to the levels of nitrates and fecal coliforms that negatively affect the quality of the waters, indicators that are not evaluated by the Dutch index. It is concluded that the proposed new index adequately evaluates water quality and proved to be an index sensitive to changes in water quality.