Caracterizacion fisica, quimica e hidromorfologica de los rios altoandinos tropicales de Ecuador y Peru

Abstract

To understand the physical, chemical and hydromorphological variability of tropical highland Andean rivers (2000 m.a.s.l.), 123 localities in eight river basins in Ecuador and Peru were sampled. The sites were selected according to their latitude, altitude, and impairment degree. The samples were taken between October 2007 and October 2008 coinciding with the dry season at both countries. In each locality both, physical and chemical (i.e., temperature, dissolved oxygen, conductivity, phosphates, nitrites, nitrates, ammonia, etc.) and hydromorphological (i.e., altitude, riparian quality index (QBR), degree of vegetal cover in the stream zone, riparian cover structure and quality, naturalness of the stream channel, aquatic habitat quality index (IHF), substrate composition, rapids frequency, elements of heterogeneity) variables were measured. At regional level (between basins), the mineralization, the hydromorphological features and the aquatic habitat heterogeneity were the most important factors explaining environmental variability. Meanwhile the temperature dissolved, oxygen and habitat heterogeneity parameters were shown to be relevant in the altitudinal gradient, while the mineralization was it in the latitudinal gradient. The importance of each factor is related to the spatial scale studied (site, basin, region). However, the altitude and variables changing with it, as temperature and dissolved oxygen, shown similar patterns regardless of the latitudinal location of the basin.