ABSTRACT The evaporation of water is an indispensable process in the earth water cycle. While high rates of evaporation made access to water resources harsher and costlier, monitoring the spatial and temporal variability of the evaporation rates, particularly in an open lake, is critical. Such information would enable to establish adequate management plans focusing on the sustainable use of available water resources. In this research, a vital lake in Lebanon, namely Karaoun or Qaraoun, was investigated. The importance of such reservoir lies in providing, solely, the required water for more than 500 000 households and 19 000 ha of agricultural lands. The evaporation rates were evaluated, both spatially and temporally, between 1985 and 2018 using the widely acknowledged Mapping EvapoTranspiration at high Resolution with Internalized Calibration (METRIC) system. This latter is based on 30 m. Landsat 4, 5, 7 and 8 satellite images. Main results emphasize the evaporation rates increase over the lake, particularly noticed since 2005. Between 1985 and 2018, the annual mean evaporation rate was 2.24 mm day−1. More precisely, the annual mean evaporation rate has nearly doubled between 1985–1989 and 2014–2018 periods (i.e. 1.87 vs. 3.12 mm day−1). Mann-Kendall test and Sen’s Slope estimates were produced to check the significance of the observed trends as well as to investigate the main driving factors behind this increase. Main causes were divided into natural (i.e. significant increase at α = 0.001 for temperatures and at α = 0.05 for solar radiations) and anthropogenic (i.e. deteriorating water quality) related factors. The most probable future scenario would highlight a fearful increase of 1°C in the next decade and an evaporation rate multiplied one and half times by 2038. These findings should help local management authority to mitigate water quality and turbidity effects, as well as to accurately estimate the water budget in an open-water lake. The concerned government should also benefit from these results to draw clear policies on how to conserve water resources with an increasing global warming trend. Such study could be portable to other regions where evaporation-related datasets are missing.

中文翻译：

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重要湖泊的蒸发率：对 Karaoun 湖的 34 年评估

摘要 水的蒸发是地球水循环中不可缺少的过程。虽然高蒸发率使获取水资源变得更加艰难和昂贵，但监测蒸发率的空间和时间变化，尤其是在开阔的湖泊中，至关重要。此类信息将有助于制定充分的管理计划，重点关注可用水资源的可持续利用。在这项研究中，调查了黎巴嫩的一个重要湖泊，即 Karaoun 或 Qaraoun。此类水库的重要性仅在于为 500 000 多户家庭和 19 000 公顷农田提供所需的水。在空间和时间上评估蒸发率，1985 年至 2018 年之间，使用广泛认可的 Mapping EvapoTranspiration 高分辨率内化校准 (METRIC) 系统。后者基于 30 m。Landsat 4、5、7 和 8 卫星图像。主要结果强调了湖泊上蒸发率的增加，尤其是自 2005 年以来。1985 年至 2018 年间，年平均蒸发率为 2.24 mm day−1。更准确地说，年平均蒸发率在 1985-1989 年和 2014-2018 年期间几乎翻了一番（即 1.87 对 3.12 mm day-1）。Mann-Kendall 检验和 Sen 的斜率估计用于检查观察到的趋势的显着性以及调查这种增长背后的主要驱动因素。主要原因分为自然原因（即温度在 α = 0.001 和 α = 0 时显着增加。05 用于太阳辐射）和人为（即水质恶化）相关因素。最有可能的未来情景将突出显示，未来 10 年气温上升 1°C，到 2038 年蒸发率将增加一倍半。这些发现应有助于地方管理当局减轻水质和浊度影响，并准确地估算开放水域湖中的水预算。有关政府也应从这些结果中受益，以便在全球变暖趋势加剧的情况下制定明确的水资源保护政策。这样的研究可以移植到缺少蒸发相关数据集的其他地区。最有可能的未来情景将突出显示，未来 10 年气温上升 1°C，到 2038 年蒸发率将增加一倍半。这些发现应有助于地方管理当局减轻水质和浊度影响，并准确地估算开放水域湖中的水预算。有关政府也应从这些结果中受益，以便在全球变暖趋势加剧的情况下制定明确的水资源保护政策。这样的研究可以移植到缺少蒸发相关数据集的其他地区。最有可能的未来情景将突出显示，未来 10 年气温上升 1°C，到 2038 年蒸发率将增加一倍半。这些发现应有助于地方管理当局减轻水质和浊度影响，并准确地估算开放水域湖泊中的水预算。有关政府也应从这些结果中受益，以便在全球变暖趋势加剧的情况下制定明确的水资源保护政策。这样的研究可以移植到缺少蒸发相关数据集的其他地区。有关政府也应从这些结果中受益，以便在全球变暖趋势加剧的情况下制定明确的水资源保护政策。这样的研究可以移植到缺少蒸发相关数据集的其他地区。有关政府也应从这些结果中受益，以便在全球变暖趋势加剧的情况下制定明确的水资源保护政策。这样的研究可以移植到缺少蒸发相关数据集的其他地区。