The spatially explicit assessment of freshwater is key to introduce the ecosystem services (ES) concept into decision-making processes. Many tools are being developed to model water balance and to analyze the effects of meteorological conditions on water ES behaviors at multiple spatial scales. The current study uses the InVEST Annual Water Yield Model (WYM) to assess water availability in watersheds of the mainland of Portugal. The methodology included sensitivity analysis to test different parameters of the model and validation using the European Environment Agency (EEA) database on the quantity of Europe’s water resources. To evaluate the models’ sensitivity, Pearson’s correlation coefficients and statistical methods were calculated for each simulation. Results at the national level show a correlation coefficient of 0.803 with statistical significance for 0.01 one-tail. Water yield was underestimated by 56.5 mm/ha/year in the North of the country and overestimated by 58.1 mm/ha/year in the South. This difference was explained through the spatial-temporal assessment of the main climatic variables used as input. This study contributes to a methodology to assess the level of confidence in the WYM outputs and can be used to support the trustworthiness of water availability studies, using open-access data and software.

中文翻译：

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产水量建模、敏感性分析和验证：针对葡萄牙的研究

淡水的空间明确评估是将生态系统服务 (ES) 概念引入决策过程的关键。正在开发许多工具来模拟水平衡并分析气象条件对多个空间尺度上的水 ES 行为的影响。当前的研究使用 InVEST 年度产水量模型 (WYM) 来评估葡萄牙大陆流域的可用水量。该方法包括敏感性分析以测试模型的不同参数，并使用欧洲环境署 (EEA) 数据库对欧洲水资源数量进行验证。为了评估模型的敏感性，我们计算了每次模拟的 Pearson 相关系数和统计方法。国家层面的结果显示相关系数为 0。803 的统计显着性为 0.01 单尾。该国北部的水产量被低估了 56.5 毫米/公顷/年，而在南部被高估了 58.1 毫米/公顷/年。这种差异是通过对用作输入的主要气候变量的时空评估来解释的。该研究有助于采用一种方法来评估对 WYM 输出的置信度，并可用于支持使用开放获取数据和软件的水资源可用性研究的可信度。