The influence of topography and land use on hydrological and nutrient dynamics in two Andean streams from Northern Patagonia

Fluvial dynamics are driven by multiple environmental factors and scales. Studies coupling hydrological and nutrient dynamics of mountain streams are almost non-existent in the Northern Patagonian region; which is characterised by a temperate-cold climate. We studied two adjacent streams with contrasting drainage basins: Casa de Piedra (41 degrees 07 ' 30.11 '' S 71 degrees 27 ' 13.16 '' W), which originates in a small mountain lake and runs through pristine landscapes, and Gutierrez (41 degrees 09 ' 36.18 '' S 71 degrees 24 ' 37.19 '' W) that originates in a large piedmont lake and runs through an anthropized landscape. The streams displayed contrasting hydrological and nutrient dynamics. Casa de Piedra had higher discharge flashiness with shorter response delays to precipitation. Whereas the hydrology of Gutierrez was buffered by the upstream lake, its nutrient exports were not. Differences observed in quality and timing in the export of coarse particulate organic matter and levels of phosphorus and nitrogen are explained by human activities affecting Gutierrez but not Casa de Piedra. Moreover, the ratio of nitrogen:phosphorus suggests that phosphorus may be the limiting nutrient in the future, at the more densely populated basin. To summarise, Northern Patagonian streams flowing under marked geological and climate similarities, display stark differences in dynamics of their adjacent basins due to differences in topography and land use.