Physico-chemical evaluation of the water quality in Rocha River: A qualitative and comparative analysis including aspects of social and environmental factors

Abstract: In this study, a physico-chemical analysis of the Rocha River was performed during the beginning of the rainy season 2018 in order to examine the current state of the water quality in the river at six different locations. The river, located in the Cochabamba department, Bolivia, was examined from upstream in Sacaba to downstream in Sipe Sipe. An additional aim was to determine social and environmental contributing factors for the water quality of the Rocha River. The chemical analysis was based on the following parameters: electrical conductivity, dissolved oxygen, 5-day biochemical oxygen demand, chemical oxygen demand, nitrates and fecal coliforms. To examine the state and range of usage for the water in Rocha River the results of the water quality for each parameter was compared with the regulations for drinking water, agriculture water and environmental water from WHO, EPA and FAO as well as Bolivian regulations. The stage and water flow of the river at respetive locations were measured and modelled in Hec-RAS to draw conclusions on how the physical parameters might affect the distribution of the pollution in Rocha River. The quality of the river water in this study was classified as “very”- and “highly polluted” water according to the performed organic pollution (ICO)-index. In line with previous studies, the deterioration has continued over the years since 1998 and has now reached even the outskirts of the valley from upstream in Sacaba to downstream in Sipe Sipe. From the results, the prominent parameters of the pollution were the low dissolved oxygen levels and high coliform concentrations at all locations downstream of Chiñata. The results of the high pollution is correlated with areas where the population is dense, the presence of industrial activity is high and the connection to sewage systems is poor or nonexistent. A main contributing factor of the pollution is that large volumes of untreated wastewater is directly discharged to the Rocha River along its course to the extent that it disturbs the possibilty of natural river restoration. Based on the Bolivian Environmental Law No.1333 and the analysed parameters, the water was classified as “D” at five out of the six sampling locations. This highly constrains the usage of the river water regarding health and environmental aspects. However, the water scarcity in the area enforces the farmers to use water from the Rocha River as irrigation, which may contribute to degradation of soil, pollution of the groundwater and induce health risks.