Side Scan Sonar Applied to water reservoir

Side Scan Sonar (SSS) is a well-known geophysical tool for underwater mapping. Using acoustic frequencies, usually from 100 to 2000 kHz, this tool can generate a very detailed bottom surface image from rivers, reservoirs, and from the sea. Very portable systems nowadays can also allow getting images from areas as shallow as 1 m depth, such as urban lakes, small rivers, and near-shore areas. This article discusses the SSS applicability for reservoir studies related to margins stability. The focus here is on the Porto Primavera Reservoir, located at the most western part of São Paulo state, 800 km from São Paulo city. With a water surface area greater than 200 km long × 11 km wide, the margins of the reservoir have been severely affected by an erosion process which started from waves created due to the large wind patches. Since a few years ago in some parts of the reservoir the margin receded 40 to 60 meters from the original border, causing some problems for the local population, to the company which manage the reservoir, and also created some environmental issues. A study based on side scan images was conducted by IPT to try to protect these margins from wave actions. Some special underwater structures were created and implemented at strategic positions on the bottom surface and also at the margin, in order to minimize the wave energy before it hits the border. During the first part of the project the SSS survey was conducted in order to find the appropriate place to set these underwater structures. On the second part of the project the SSS survey was conducted in order to monitor these underwater structures. Successful field operations and detailed images obtained from more than 300 km of SSS survey lines showed how important this geophysical tool is for reservoir investigation.