Central Europe, a region composed of Austria, Czech Republic, Germany, Hungary, Poland, Slovakia and Slovenia, occupying over 1 million km² and inhabited by >150 million people, has recently experienced several extensive and severe hydrological droughts (e.g., 2015, 2018, 2019) that affected a wide range of sectors. These drought events were broadly attributed to climate change, but often without, or with only limited, scientific assessment. There is a common belief that warmer climate and more frequent heat waves are likely to lead to more severe hydrological droughts in the future. However, there is lack of robust findings that would hold at either national or regional scale, so that comparison of these findings is of broad relevance and interest in the region. This systematic-style review attempts to identify the evidence for: (1) historical trends in observed data and (2) changes in model-based projections for the future, in low river flow and hydrological drought indices in rivers of Central Europe. In the context of this review, focusing on directions rather than magnitude of historical and future changes, we were treating hydrological droughts and low flows as synonyms. To address these questions, we searched Web of Science and Scopus databases and screened 976 abstracts to identify 68 articles fulfilling all inclusion criteria from which metadata were extracted and analyzed. The results show that overall, trends detected in observation records have more frequently downward (i.e. meaning decreased low flows or increased drought hazard) than upward direction (53% vs. 11%). However, the frequency of evidence reporting decreases in future low flows is lower for future projections than for historical trends (43% vs. 53%), and even more convincingly, nearly three times more evidence items point out at upward trends in the future (31% vs. 11%). This shows that there is a low coherence between observed and projected indices of low river flows in Central Europe. Catchment topography appears to be an important factor affecting trend direction: in mountainous catchments only 33% of evidence items pointed out at increasing hydrological drought hazard, whereas in other types of catchments this frequency was almost doubled. A striking difference in dominant future direction of changes between studies based on SRES and RCP scenarios was identified: in the former only 6% of evidence items pointed out at less severe hydrological drought hazard in the future, while in the latter it was 42%. Finally, systematic review approach enabled us to identify some knowledge gaps, such as studies on low flow historical trends in lowland and upland catchments as well as in large river basins.

中欧，由奥地利、捷克共和国、德国、匈牙利、波兰、斯洛伐克和斯洛文尼亚组成，面积超过 100 万平方公里²并居住着超过 1.5 亿人，最近经历了数次广泛而严重的水文干旱（例如，2015 年、2018 年、2019 年），影响了广泛的部门。这些干旱事件广泛归因于气候变化，但往往没有或只有有限的科学评估。人们普遍认为，气候变暖和热浪更频繁可能会导致未来更严重的水文干旱。然而，缺乏适用于国家或地区范围的强有力的调查结果，因此这些调查结果的比较在该地区具有广泛的相关性和兴趣。这种系统式的审查试图确定以下证据：（1）观测数据的历史趋势和（2）基于模型的未来预测的变化，中欧河流的低河流流量和水文干旱指数。在本次审查的背景下，我们关注的是方向而不是历史和未来变化的幅度，我们将水文干旱和低流量视为同义词。为了解决这些问题，我们搜索了 Web of Science 和 Scopus 数据库并筛选了 976 篇摘要，以确定 68 篇满足提取和分析元数据的所有纳入标准的文章。结果表明，总体而言，观测记录中检测到的趋势向下（即意味着低流量减少或干旱风险增加）比向上（53% 对 11%）更频繁。然而，未来预测的证据报告在未来低流量中减少的频率低于历史趋势（43% 对 53%），甚至更有说服力，近三倍的证据表明未来有上升趋势（31% 对 11%）。这表明中欧低河流流量的观测指数和预测指数之间的一致性较低。流域地形似乎是影响趋势方向的一个重要因素：在山区流域中，只有 33% 的证据表明水文干旱灾害增加，而在其他类型的流域中，这一频率几乎翻了一番。确定了基于 SRES 和 RCP 情景的研究在未来主要变化方向上的显着差异：在前者中，只有 6% 的证据表明未来水文干旱灾害不太严重，而在后者中这一比例为 42%。最后，系统评价方法使我们能够发现一些知识差距，