Although global- and catchment-scale hydrological models are often shown to accurately simulate long-term runoff time-series, far less is known about their suitability for capturing hydrological extremes, such as droughts. Here we evaluated simulations of hydrological droughts from nine catchment scale hydrological models (CHMs) and eight global scale hydrological models (GHMs) for eight large catchments: Upper Amazon, Lena, Upper Mississippi, Upper Niger, Rhine, Tagus, Upper Yangtze and Upper Yellow. The simulations were conducted within the framework of phase 2a of the Inter-Sectoral Impact Model Intercomparison Project (ISIMIP2a). We evaluated the ability of the CHMs, GHMs and their respective ensemble means (Ens-CHM and Ens-GHM) to simulate observed hydrological droughts of at least one month duration, over 31 years (1971–2001). Hydrological drought events were identified from runoff-deficits and the Standardised Runoff Index (SRI). In all catchments, the CHMs performed relatively better than the GHMs, for simulating monthly runoff-deficits. The number of drought events identified under different drought categories (i.e. SRI values of -1 to -1.49, -1.5 to -1.99, and ≤-2) varied significantly between models. All the models, as well as the two ensemble means, have limited abilities to accurately simulate drought events in all eight catchments, in terms of their occurrence and magnitude. Overall, there are opportunities to improve both CHMs and GHMs for better characterisation of hydrological droughts.

尽管全球和流域尺度的水文模型经常被证明可以准确地模拟长期径流时间序列，但对于它们是否适合捕捉干旱等极端水文模型却知之甚少。在这里，我们评估了来自 9 个流域尺度水文模型 (CHMs) 和 8 个全球尺度水文模型 (GHMs) 对 8 个大型流域的水文干旱模拟：亚马逊河上游、勒拿河上游、密西西比河上游、尼日尔河上游、莱茵河、塔霍河、扬子河上游和黄河上游. 模拟是在跨部门影响模型比对项目 (ISIMIP2a) 阶段 2a 的框架内进行的。我们评估了 CHM、GHM 及其各自的集合平均值（Ens-CHM 和 Ens-GHM）在 31 年（1971-2001 年）中模拟观察到的至少一个月持续时间的水文干旱的能力。从径流赤字和标准化径流指数 (SRI) 中确定了水文干旱事件。在所有流域中，在模拟月径流赤字方面，CHM 的表现相对优于 GHM。不同干旱类别下确定的干旱事件数量（即 SRI 值为 -1 至 -1.49、-1.5 至 -1.99 和≤-2）在模型之间存在显着差异。所有模型，以及两个集合方法，在准确模拟所有八个流域的干旱事件的发生率和规模方面的能力有限。总体而言，有机会改进 CHM 和 GHM，以更好地表征水文干旱。用于模拟月径流赤字。不同干旱类别下确定的干旱事件数量（即 SRI 值为 -1 至 -1.49、-1.5 至 -1.99 和≤-2）在模型之间存在显着差异。所有模型，以及两个集合方法，在准确模拟所有八个流域的干旱事件的发生率和规模方面的能力有限。总体而言，有机会改进 CHM 和 GHM，以更好地表征水文干旱。用于模拟月径流赤字。不同干旱类别下确定的干旱事件数量（即 SRI 值为 -1 至 -1.49、-1.5 至 -1.99 和≤-2）在模型之间存在显着差异。所有模型，以及两个集合方法，在准确模拟所有八个流域的干旱事件的发生率和规模方面的能力有限。总体而言，有机会改进 CHM 和 GHM，以更好地表征水文干旱。就它们的发生和大小而言。总体而言，有机会改进 CHM 和 GHM，以更好地表征水文干旱。就它们的发生和大小而言。总体而言，有机会改进 CHM 和 GHM，以更好地表征水文干旱。