Title : Topography and Land Use Modulate Hydrological and Nutrient Export Dynamics in 4 Andean Streams 5 Short Title : Hydrology and Nutrient exports in Andean streams

28 Waterways act as integrators of ecosystems, their dynamics driven by multiple environmental factors and scales. 29 To elucidate factors affecting hydrological and nutrient dynamics in Andean streams, we characterized two 30 adjacent North Patagonian streams with contrasting drainage basins: Casa de Piedra (CP), originating in a small 31 mountain lake and running through a pristine landscape, and Gutiérrez (G), originating in a large piedmont lake 32 and running through an anthropized landscape. The drainage basins share both temperature and precipitation 33 regimes; however, the streams presented contrasting hydrological dynamics and nutrient export values. CP had 34 higher discharge flashiness with shorter response delays to precipitation, while G showed more stable 35 hydrograms, a difference explained by buffering from a large upstream lake in G’s basin. Streams showed 36 differences in the quality and timing of coarse particulate organic matter export and basal export levels of 37 phosphorus and nitrogen that could be explained by human activities affecting G but not CP. Moreover, 38 nitrogen:phosphorus ratio indicates a possible shift to phosphorus as the limiting nutrient in the future in G 39 drainage basin. In summary, our results show that even under a common climatic regime, dynamics of adjacent 40 basins can be strongly driven by topographic and land use factors. 41