Summary

Description

This study compared bathymetric models generated from topographic data collected with: 1 a recreational Lowrance HDS Gen 2 sonar fish finder, and 2 a survey grade Realtime Kinematic RTK GPS unit using traditional topographic surveying techniques, at the Middle 395 and Headquarters ponds at the Modoc National Wildlife Refuge MNWR in August and October of 2013. The purpose of the study was to assess the suitability of the fish finder, which is low cost, for generating bathymetric data from wetlands and ponds at the MNWR.Digital Elevation Models DEMs of each pond were developed from pond bottom topographic data generated through the RTK GPS and sonar surveys. A smoothed DEM was used for contour creation and for graphical display, but was not used for analysis. The magnitude of elevation differences was calculated between concurrent DEMs developed for each pond, and the distribution of these differences were analyzed.The sonar system was found to be preferable in ponds with areas larger than 4 hectares 10 acres and deeper ponds with average depths greater than 0.6 m 2 ft where the shallow water limitation is encountered less frequently and where an RTK survey would be resource intensive to implement.