The Major River Basins in Madagascar (MRBM) play a crucial role in providing water to the Malagasy population as well as the ecosystem. Little is known about the impact of climate change on these basins, and it is not clear what factors have the most significant impact on them. There are two central objectives of this study: 1. To assess the future potential water available for daily life and agriculture use across the MRBM. 2. To compare the projected change within the MRBM with the historical trends analysis and identify the water-stressed basins. In this paper, a new method for assessing the future available Intra-basin water resources combined with the impacts of climate change, land use, and population is proposed. Three imbalance indicators are introduced to quantify the spatial availability (indicator N°1), distribution (indicator N°2), and variability (indicator N°3) of the Potential Water Resources (PWR) available and have been applied to the MRBM. Under the SSP2–4.5 scenario, results showed a decreasing trend of the PWR in most of the basins by 2050 with a rise in evapotranspiration and a decline in precipitation. The increasing trend and uneven distribution of the population and agricultural land upstream/downstream are found to cause the reduction of the PWR available per capita (by 37 %) and agriculture area (by 69 %) across the MRBM. This study predicts water scarcity for most of the basins by 2050, especially in the Mangoro and Onilahy Basins. Upstream populations are expected to grow in Mahajamba, Mahavavy, Betsiboka, Manambolo, Tsiribihina, Mangoro, Onilahy, Mananara, and Mandrare basins, along with an expansion of the downstream agricultural land in Sofia, Betsiboka, Manambolo, Mangoky, and Mandrare basins. These findings enhance the cause-effect relationship between climate change, land use change, population growth, and water scarcity in the MRBM. Urgent action is therefore needed for an efficient and sustainable management of these water-stressed basins.

中文翻译：

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评估马达加斯加未来流域内可用水量：考虑气候变化、人口增长和土地利用变化


马达加斯加的主要河流流域 (MRBM) 在为马达加斯加人口和生态系统供水方面发挥着至关重要的作用。人们对气候变化对这些流域的影响知之甚少，也不清楚哪些因素对其影响最显着。本研究有两个中心目标： 1. 评估 MRBM 未来日常生活和农业用水的潜力。 2. 将 MRBM 的预测变化与历史趋势分析进行比较，并确定缺水流域。本文提出了一种结合气候变化、土地利用和人口影响评估未来可用流域内水资源的新方法。引入了三个不平衡指标来量化可用潜在水资源（PWR）的空间可用性（指标 N°1）、分布（指标 N°2）和变异性（指标 N°3），并已应用于 MRBM。在SSP2-4.5情景下，结果显示，到2050年，大部分流域的压水堆呈下降趋势，蒸散量增加，降水量减少。研究发现，上游/下游人口和农业用地的增长趋势和分布不均导致整个MRBM的人均可用压水堆（减少37％）和农业面积（减少69％）。这项研究预测到 2050 年，大多数盆地将出现缺水，特别是曼戈罗盆地和奥尼拉希盆地。 Mahajamba、Mahavavy、Betsiboka、Manambolo、Tsiribihina、Mangoro、Onilahy、Mananara 和 Mandrare 盆地的上游人口预计将增长，同时索非亚、Betsiboka、Manambolo、Mangoky 和 ​​Mandrare 盆地下游农业用地也会扩大。 这些发现增强了 MRBM 中气候变化、土地利用变化、人口增长和水资源短缺之间的因果关系。因此，需要采取紧急行动，对这些缺水流域进行有效和可持续的管理。