Matemática e Estatística / Mathematics and Statistics
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Browsing Matemática e Estatística / Mathematics and Statistics by Sustainable Development Goals (SDG) "06:Água Potável e Saneamento"
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- Modeling water level fluctuation in river basins using singular spectrum analysisPublication . Oliveira, Amilcar; Sarmento, CarlaWater scarcity affected 29% of the EU territory during at least one season in 2019. In the face of climate change, it is very important to understand the risk of water scarcity. Water scarcity is becoming a growing problem in southern European countries, such as Portugal. In 2019, Portugal, faced one of the most significant water scarcity conditions in the EU-27 on the seasonal scale (seasonal WEI 66%).The main objective of this work is to study the water level fluctuation in river basins, in order to predict the risks of lack of water. The study area is located in 29 reservoirs from different river basins in Portugal. The collected data refer to the period from November 1993 to August 2022, with a total number of records of 9686. We started by improving the quality of the data and built a monthly time series of the volume of water stored. Next, we analyzed the time series using Singular Spectrum Analysis (SSA), which is a nonparametric technique for analyzing time series.
- A strategy to assess water meter performancePublication . Cordeiro, Clara; Borges, Ana; Ramos, Maria do RosárioApparent water losses can be problematic to water companies’ revenues. This type of loss is very difficult to detect and quantify and is often associated with water meter anomalies. This study was motivated by a water company’s challenge that links a decrease in water consumption to water meters’ malfunction. The aim is to develop a strategy to detect decreasing water usage patterns, contributing to meter performance assessment. The basis of the approach is a combination of statistical methods. First, the time series of billed water consumption is decomposed using Seasonal-Trend decomposition based on Loess. Next, breakpoint analysis is performed on the seasonally adjusted time series. After that, the Mann–Kendall test and Sen’s slope estimator are used to analyze periods of progressive decrease changes in water consumption, defined by breakpoints. A quantitative indicator of this change is proposed. The strategy was successfully applied to eight-time series of water consumption from the Algarve, Portugal.