Abstract
Covering an area of approximately 97 km2 and with a maximum depth of 58 m, Lake Trichonis is the largest and one of the deepest natural lakes in Greece. As such, it constitutes an important ecosystem and freshwater reserve at the regional scale, whose qualitative and quantitative properties ought to be monitored. Depth is a crucial parameter, as it is involved in both qualitative and quantitative monitoring aspects. Thus, the availability of a bathymetric model and a reliable DTM (Digital Terrain Model) of such an inland water body is imperative for almost any systematic observation scenario or ad hoc measurement endeavor. In this context, the purpose of this study is to produce a DTM from the only official cartographic source of relevant information available (dating back approximately 70 years) and evaluate its performance against new, independent, high-accuracy hydroacoustic recordings. The validation procedure involves the use of echosoundings coupled with GPS, and is followed by the production of a bathymetric model for the assessment of the discrepancies between the DTM and the measurements, along with the relevant morphometric analysis. Both the production and validation of the DTM are conducted in a GIS environment. The results indicate substantial discrepancies between the old DTM and contemporary acoustic data. A significant overall deviation of 3.39 ± 5.26 m in absolute bottom elevation differences and 0.00 ± 7.26 m in relative difference residuals (0.00 ± 2.11 m after 2nd polynomial model corrector surface fit) of the 2019 bathymetric dataset with respect to the ~1950 lake DTM and overall morphometry appear to be associated with a combination of tectonics, subsidence and karstic phenomena in the area. These observations could prove useful for the tectonics, geodynamics and seismicity with respect to the broader Corinth Rift region, as well as for environmental management and technical interventions in and around the lake. This dictates the necessity for new, extensive bathymetric measurements in order to produce an updated DTM of Lake Trichonis, reflecting current conditions and tailored to contemporary accuracy standards and state-of-the-art research in various disciplines in and around the lake.
Highlights
Lakes and reservoirs serve as the main source of the liquid surface freshwater and are important indicators of worldwide non-freezing freshwater storage [1]
The present study was concerned with the evaluation of a digital terrain model from existing topographic mapping data sources of Lake Trichonis, using recent bathymetric information acquired through the processing of hydroacoustic and GPS data
Hydroacoustic data were collected along a transect covering the area of the lake in a coil-shaped pattern and were converted to bathymetric information using appropriate processing steps
Summary
Lakes and reservoirs serve as the main source of the liquid surface freshwater and are important indicators of worldwide non-freezing freshwater storage [1]. They serve as plant, animal and microorganism habitats; offer resources for human exploitation; and can be used to purify and regulate water flows. The morphometric characteristics of inland water bodies and their variations over time influence the physical, chemical and biological processes [5], while a number of applications, such as underwater topography monitoring, assessment of morphometric characteristics and water level or deposited sediment estimation, rely on the accurate determination of depth. The quality and reliability of this information is a direct function of the corresponding precision and accuracy of bathymetric maps [6], and of available digital terrain models, which represent the “bare Earth” topography [7]
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