Past streamflow variability of the Shullcas River in the Peruvian Andes inferred from tree-rings records

Improving the understanding and predicting the hydrological behaviour of headwaters in the context of climate change has enormous socioeconomic impacts. The central region of Peru constitutes a major food supplier to nearby cities and to Lima, Peru’s capital. Moreover, this region faces seasonal water shortages which may increase drought impacts putting water availability at risk. The use of tree-ring records for characterizing long-term climatic variability has improved estimates of extreme hydroclimatic events contributing to a better management of water resources in several regions of the world. In this study, we investigate past changes in the streamflow variability of Shullcas river by means of two Polylepis rodolfo-vasquezii tree-ring chronologies located at an elevation of 3900 m a.s.l. in the Central Andean range (1.65°S, 74.96°W). We generated a streamflow reconstruction for the Shullcas river that spans for the period 1856-2013 and is the first streamflow reconstruction for the dry season (July to October) in the Peruvian central Andes. The reconstruction calibration model used a regional tree-ring width record composed by the two P. rodolfo-vasquezii chronologies and 27 streamflow observations between 1986 and 2013 for the dry season. The tree-ring based streamflow reconstruction reveals a negative trend in streamflow since the 1990s unprecedent in the previous century. This study enables us to understand past streamflow variability to give a context to current trends and improve the management of the water resources in the Shullcas basin. It also underscores the importance of developing new tree-ring records across the central Andes to enhance the study of past climatic and hydrological processes.