Tree-ring indicators of rainfall and streamflow for the Ili-Balkhash Basin, Central Asia since CE 1560

Abstract

We reconstructed previous July–current April total precipitation in the upper Ili-Balkhash Basin of Central Asia, using a transfer equation based on the correlation between regional tree-ring width series and local precipitation data. Dry periods were identified from 1586–1612, 1637–1669, 1695–1721, 1759–1782, 1804–1864, 1907–1930 and 1974–1993, while wet periods occurred from 1560–1585, 1613–1636, 1670–1694, 1722–1758, 1783–1803, 1865–1906, 1931–1973 and 1994–2006. Spatial correlation analysis indicates that our precipitation reconstruction is broadly representative of precipitation in the entire Ili-Balkhash Basin. The precipitation timeseries is also strongly related to streamflow measurements, revealing that variations in precipitation in the upper Ili-Balkhash Basin have a dramatic influence on streamflow into Lake Balkhash. The precipitation reconstruction also compares well with various streamflow reconstructions from the Tien Shan, and exhibits an increasing streamflow trend in the 1980s through 2000s. Spectral analysis showed significant 60-, 33-, 11-, 2.8- and 2.1-year cycles over the past 447years. Our 447-year precipitation reconstruction provides the basis for comparing past and present hydroclimate changes, which will be important for detection and attribution of hydroclimate variation in the Ili-Balkhash Basin.