Ecosystem loss assessment following hydroelectric dam flooding: The case of Yacyretá; Argentina

Abstract

The Yacyretá dam is one of the most important hydroelectric projects in La Plata Basin.As a consequence of the filling of the reservoir to its final height of 83 meters; approximately 1;076 km2 of terrestrial and riparian ecosystems were flooded in Argentina and Paraguay. In order to evaluate the ecosystems loss due to this impounding; we generated two maps of land use/land cover from Landsat satellite images: 1987 (prior to the dam) and 2011 (after the final height was reached). We applied a post classification method and tested the gain; loss; and net change of natural and anthropic ecosystems in the study area with a cross tabulation matrix. Water bodies were the land cover type that showed the greatest degree of change; increasing 14.8% between periods. This was in detriment of; primarily; wetlands by 7.5%; grasslands by 4.0%; and native forests by 2.8%. However; sandbanks presented the highest probability of transition to another land class and; thus; correspond to the most vulnerable land covering the study area. Also; we detected a differential ecosystem loss; both in type and magnitude; up and downstream of the dam. Our work is the first one to address ecosystem loss in the Yacyretá area and our results should help to improve management policies; such as the design of the current network of compensatory reserves.