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<p>The increasing importance of inland water bodies in meeting human needs—especially in recent years—has emphasized the necessity of monitoring freshwater availability. The Surface and Ocean Topography (SWOT) mission introduced a different approach for observing surface water dynamics, aiming to achieve high spatial and temporal resolution. In this study, we present a methodology that utilizes the SWOT PIXel Cloud product (PIXC) from the SWOT mission to obtain water level variations in the largest, by area, lakes across Greece. The methodology aims to remove unreliable values prior to computing the water level, where, apart from the provided quality and accuracy flags, the phase noise standard deviation of the measurements was found to have a significant impact. The obtained satellite-derived water surface elevations are validated against <i>in situ</i> water level gauge stations to assess their accuracy and consistency. An additional evaluation is carried out using <i>in situ</i> GNSS buoy measurements, which were obtained concurrently with those from SWOT in Lake Volvi. Next, a comparison is made against the Lake Single-Pass (Lake SP) product, while the geoid model used for deriving water level heights is also examined. From our study, we conclude that SWOT does not provide the expected temporal coverage as initially anticipated due to unreliable measurements. Its accuracy though for the study area, when taking the average of water elevations per lake, ranges between 13 and 19 cm, when compared to permanent monitoring stations. The high resolution cannot be exploited due to the high variability of the measurements, even after further processing. Last, we provide water level variations for lakes in Greece that do not have a permanent water level monitoring station installed.</p>

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Computation and validation of lake water levels in Greece using SWOT satellite data

  • 期刊论文

  • 出版模式：

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  • 发表日期：

    2026年5月19日

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  • Thomais D. Ippeki,
  • Vassilios N. Grigoriadis

摘要

The increasing importance of inland water bodies in meeting human needs—especially in recent years—has emphasized the necessity of monitoring freshwater availability. The Surface and Ocean Topography (SWOT) mission introduced a different approach for observing surface water dynamics, aiming to achieve high spatial and temporal resolution. In this study, we present a methodology that utilizes the SWOT PIXel Cloud product (PIXC) from the SWOT mission to obtain water level variations in the largest, by area, lakes across Greece. The methodology aims to remove unreliable values prior to computing the water level, where, apart from the provided quality and accuracy flags, the phase noise standard deviation of the measurements was found to have a significant impact. The obtained satellite-derived water surface elevations are validated against in situ water level gauge stations to assess their accuracy and consistency. An additional evaluation is carried out using in situ GNSS buoy measurements, which were obtained concurrently with those from SWOT in Lake Volvi. Next, a comparison is made against the Lake Single-Pass (Lake SP) product, while the geoid model used for deriving water level heights is also examined. From our study, we conclude that SWOT does not provide the expected temporal coverage as initially anticipated due to unreliable measurements. Its accuracy though for the study area, when taking the average of water elevations per lake, ranges between 13 and 19 cm, when compared to permanent monitoring stations. The high resolution cannot be exploited due to the high variability of the measurements, even after further processing. Last, we provide water level variations for lakes in Greece that do not have a permanent water level monitoring station installed.