FILYOS RIVER STREAMFLOW RECONSTRUCTION FROM TREE-RING CHRONOLOGIES WITH NONPARAMETRIC APPROACHES

The article presents nonparametric methods based on K nearest neighbors (KNNs), modified KNNs, and local polynomial techniques to reconstruct streamflow ensembles from tree-ring data in Filyos River region (Turkey). Three methods were tested using cross-validation for the overlap period, 1963-1997 for which the tree-ring and streamflow data are available. It was found that for the study where the length of the overlap period was limited, a nonparametric method based on a local polynomial technique provides simulations that have a slightly better solution than the other methods. After verification using standard statistical techniques, these methods were utilized to develop streamflow reconstructions from tree-ring data for the paleo-hydrologic period (1657-1963). These reconstructions of seasonal low and high flows were discussed with the obtained flood duration curve. They were also compared with the historical archives and other tree-ring reconstructions data available in the same river. Overall, the utility and limitations of these methods and the resulting streamflow simulations were discussed to assess the long-term discharge behavior of Filyos River and to evaluate water supply reliability.