Investigation of Volumetric Variation from Water Supply Reservoir by using Different Spaces between the Regular Bathymetric Sections

Abstract

Bathymetry is the study of submerged areas such as lakes, rivers, reservoirs, or oceans floors. Furthermore, its main aim is to represent graphically these areas throughout of digital surface by using measured depths. The detailing of these surfaces is affected by the bathymetric data spatial-distribution and the single-beam echo-sounder standard specifications. Therefore, the Digital Elevation Model (DEM) accuracy is related to these precepts and so infers to the surface-volume precision. During the bathymetric survey, held in the pre-reservoir of Passaúna which is located in the Curitiba’s metropolitan region (Brazil), we planned an offset of 15 meters between the Regular Bathymetric Sections (RBS) and, during the post-processing, this offset was increased every 15 meters until reach up to 300 meters. For each dataset, many models were determined by using interpolators such as Kriging method (KRG) and the Inverse Distance Weighted (IDW) and, from them, we computed the residuals by comparing the probed (obtained on the check lines) and the interpolated depths (from DEM). Also, the residuals Root Mean Square (RMS), an average value of 0.18 m was found on DEM generated using the RBS spaced from 15 to 105 meters and interpolated using the IDW method; its bathymetric data was positioned using the single-frequency GPS receptor (WS3910). By comparison between surface-volumes, we found a volumetric discrepancy up to -4.76% on DEM with RBS spaced from 30 meters to 180 meters; as the reference model, we used all surface model generated by using data from RBS spaced in 15 m due to its greatest accuracy.