Brazil's Northeast region (BRN), especially the state of Ceará (CE), has dealt historically with severe drought events since the late 1800s, which commonly led to catastrophic impacts of mass migration and deaths of thousands of people. Throughout the last century, the “Droughts Polygon” region experienced an intense infrastructural development, with the expansion of a dense network of reservoirs. This paper presents a parsimonious hydrologic modeling approach to investigate the 100-year (1920–2020) evolution of the hydrology of the 24,500 km² Upper Jaguaribe Basin, throughout the development of a dense reservoir network. We aimed at reproducing the hydrology at the basin scale and analyzed the outcomes of reservoir expansion in terms of water fluxes and water security. Our model's structure captured the growth in reservoir count and storage capacity, which was then confronted with an evolving water demand, allowing us to estimate how water security (i.e., proportion of demand being met) varied over the 100-year period. Significant streamflow reduction at the basin's outlet and increase in evaporation losses, associated with a decrease in streamflow at varying exceedance frequencies were observed at the end of the study period. While reservoir expansion allowed for the transition from complete vulnerability to meteorological droughts to increased levels of water security, drought impacts had, in the meantime, disproportionally intensified, especially in reservoirs of medium to small capacities. Smaller reservoirs are suggested to have played the role of distributing water resources throughout the region, while larger reservoirs were more efficient as tools to promote water security.

中文翻译：

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巴西半干旱地区 100 年来的水库扩建，缓解干旱和水安全的演变


巴西东北地区 (BRN)，特别是塞阿拉州 (CE)，自 1800 年代末以来一直遭受严重干旱事件，通常会导致大规模移民和数千人死亡的灾难性影响。在整个上个世纪，“干旱多边形”地区经历了基础设施的大力发展，水库网络不断扩大。本文提出了一种简约的水文建模方法，用于研究 24,500 km ²上雅瓜里贝盆地在密集水库网络发展过程中的 100 年（1920-2020）水文演变。我们的目标是再现流域尺度的水文，并从水通量和水安全方面分析水库扩建的结果。我们的模型结构捕捉了水库数量和存储容量的增长，然后面临不断变化的水需求，使我们能够估计水安全（即满足需求的比例）在 100 年间如何变化。在研究期结束时，观察到流域出口处的水流显着减少，蒸发损失增加，这与不同超标频率的水流减少有关。虽然水库扩建使气象干旱的完全脆弱性转变为提高水安全水平，但与此同时，干旱影响却不成比例地加剧，特别是在中小容量的水库中。较小的水库被认为在整个地区发挥了分配水资源的作用，而较大的水库作为促进水安全的工具更有效。