The potential use of tree-rings to reconstruct streamflow and estuarine salinity in the Valdivian Rainforest eco-region, Chile

Water availability is one of the main limitations for future development and economic activity in many regions of the world. This applies even to areas of relatively high annual rainfall, such as the Valdivian Rainforest eco-region in Chile (35–48°S). Streamflow and water availability are crucial for several economic activities in the eco-region including hydroelectricity, irrigation, salmon farming, sports fishing of introduced trout and tourism. Scientific research focused on the spatial and temporal patterns of streamflow is a key element for planning the future development within the eco-region. In this paper we explore the potential of tree-rings for streamflow reconstruction in this region. Our preliminary results indicate a significant correlation (r=0.59 P<0.001, 1929–2000) between prior summer Río Bueno streamflow (January–April) and the average between a composite tree-ring chronology using Pilgerodendron uviferum from Chile and two composite Austrocedrus chilensis chronologies from Argentinean Patagonia. Similarly, there is a significant correlation (r=0.57, P<0.001, 1943–2002), between the Austrocedrus chronology (40°44′S) at Centinela in Argentinean Patagonia and the previous spring through early autumn (November–April) streamflow for Río Puelo. The tree-ring records used to correlate with Río Bueno and Río Puelo discharges show low-frequency variability and therefore the potential to reconstruct this variability in streamflow for the last 500–780 years. We also found a significant correlation between the composite Pilgerodendron standard ring-width chronology and the current summer water salinity (January–April) at the Reloncavi Estuary (r²=0.60, P<0.01, 1992–2000). Water salinity is a crucial determinant of the carrying capacity of salmon farming. Future research should provide reconstructions of streamflow, water salinity and other water quality attributes from tree-rings. These data will provide inputs to modeling scenarios of future water availability and are crucial to decision-making and planning of resource management and socio-economic development in the Valdivian Rainforest eco-region.