Droughts are natural hazards characterized by a prolonged period of below-average precipitation. Water scarcity is defined as insufficient water resources to meet demands in a region. This paper examines three regions (Spain, California, and the Murray-Darling Basin in Australia) which share similar social and climatic characteristics and face severe water-scarcity problems. The frequency and persistence of droughts in these regions over the last few decades have triggered changes in water laws as well as in the behaviour of water users and managers. This paper compares the major water reforms in these regions and the achievements and failures of the various approaches implemented. This comparison shows how, despite the differences in institutions and governance regarding water allocation in the three regions, recent droughts have catalysed the creation of institutions and the implementation of sophisticated long-term measures to mitigate the impact of future droughts. A deeper understanding of the effectiveness of mechanisms and regulations is necessary to better manage droughts since the uncertain impacts of climate change will require responses of a more effective nature.

干旱是自然灾害，其特征是长期降雨低于平均水平。缺水的定义是水资源不足，无法满足该地区的需求。本文研究了三个具有相似社会和气候特征并面临严重缺水问题的地区（西班牙，加利福尼亚和澳大利亚的墨累达令盆地）。在过去的几十年中，这些地区干旱的频率和持续性引发了水法以及用水者和管理者行为的变化。本文比较了这些地区的主要水改革以及所采用的各种方法的成败。这种比较表明，尽管在这三个地区的水分配制度和管理上存在差异，最近的干旱促进了机构的建立和复杂的长期措施的实施，以减轻未来干旱的影响。为了更好地管理干旱，必须对机制和法规的有效性有更深入的了解，因为气候变化的不确定影响将要求采取更有效的应对措施。