EFFECTS OF PRODUCTIVE ACTIVITIES ON THE WATER QUALITY FOR HUMAN CONSUMPTION IN AN ANDEAN BASIN, A CASE STUDY

Productive activities such as agriculture and livestock have transformed the Andean basins in South America. In accordance with this statement, the objective of this study was to assess the water quality of “Las Piedras” river located in an Andean basin with 6626 ha in Colombian Highlands. This study analyzed nutrient inputs from agricultural production, spatial crops distribution, human activities and their influence on the ecological state of the river. The evaluation integrated physicochemical and biological parameters in the indexes of water quality, pollution and the aquatic macroinvertebrates community. Results showed that aggregated crop fields occupy 25.2 % in the basin and the biological water quality through the Biological Monitoring Working Party (BMWP) index denotes the presence of tolerant-pollution organisms, additionally the biodiversity was low (Shannon H ´ 1.1). The water quality in the river satisfies the Colombian regulation criteria for human consumption, even higher concentrations of nutrients in the lower area with 2.20 mg/L nitrates and 1.49 mg/L of phosphates, besides the loss of nutrients by runoff, which was 2.57 mg/L nitrates in the middle area and 0.18 mg/L phosphates in the upper area. In this sense, the nutrient concentration input increases toward the lower area of the basin because of the crop distribution. The agricultural land use modified the hydrological ecosystem services by decreasing the basin water regulatory capacity and nutrients input to the main stream.