Water quality and sedimentation implications of installing a hydroelectric dam on the Río Baker in Chilean Patagonia

Abstract

HidroAysen, a Chilean corporation operated by energy giant Endesa, has proposed to build two hydroelectric dams on the Rio Baker in the Aysin Region of Chilean Patagonia. The proposed dams have been met with a variety of opposition and support from various parties throughout the world. Opponents of the dams argue that dam installation is unwise environmentally and socially; supporters argue that it is necessary to meet growing energy demand in Chile. The history of large dams has shown that newly installed impoundments alter the water quality of the original riverine system. Often temperatures, dissolved oxygen levels, and sediment loads in the reservoir and outflowing water are entirely different from those in the original free-flowing river; these differences alter aquatic ecology. With this in mind, this study employed surface-water modeling and hand calculations to forecast water quality in the reservoir that would be formed by the northernmost dam on the Rio Baker. Coupling IntroGLLVHT, a hydrodynamic and transport model, with a sedimentation analysis developed by Brune (1953), provides the basis for estimating water quality and sediment load changes due to dam construction. By and large, IntroGLLVHT simulations indicate that water quality in the resulting reservoir system will likely be similar to that of the original riverine system. Short hydraulic residence time and low nutrient loading facilitate this result. Conversely, sediment computations indicate that sedimentation and erosion issues are likely for the future dam-and-reservoir system.