Understanding changes in water availability is critical for Central Asia; however, long streamflow reconstructions extending beyond the period of instrumental gauge measurements are largely missing. Here, we present a 785-year-long streamflow reconstruction from spruce tree rings from the Tien Shan Mountains. Although an absolute causal relationship can not be established, relatively high streamflow rates coincided roughly with the period of Mongol expansion from 1225 to 1260 CE and the rise of the Timurid Empire from 1361 to 1400 CE. Since overall wetter conditions were further found during the Zunghar Khanate period 1693–1705 CE, we argue that phases of streamflow surplus likely promoted oasis and grassland productivity, which was an important factor for the rise of inner Eurasian steppe empires. Moreover, we suggest that the streamflow variation might be critical for plague outbreaks in Central Asia, and propose several explanations for possible links with Europe’s repeated Black Death pandemics. We demonstrate that 20th-century low streamflow is unprecedented in the past eight centuries and exacerbated the Aral Sea crisis, which is one of the most staggering ecological disasters of the twentieth century.

了解水资源可用性的变化对中亚至关重要；然而，延伸到仪器仪表测量时间之外的长水流重建在很大程度上缺失。在这里，我们展示了一个长达 785 年的溪流重建，它来自天山山脉的云杉年轮。虽然无法建立绝对的因果关系，但相对较高的流量大致与公元 1225 年至 1260 年蒙古扩张时期和公元 1361 年至 1400 年帖木儿帝国崛起时期相吻合。由于在公元 1693-1705 年的准噶尔汗国时期进一步发现了整体更湿润的条件，我们认为河流盈余阶段可能促进了绿洲和草原生产力，这是内欧亚草原帝国崛起的一个重要因素。而且，我们认为水流变化可能对中亚的鼠疫爆发至关重要，并就与欧洲反复出现的黑死病大流行的可能联系提出了几种解释。我们证明了 20 世纪的低流量在过去八个世纪中是前所未有的，并加剧了咸海危机，这是 20 世纪最令人震惊的生态灾难之一。