Complex sentence: Thousands of spawning salmon originally ran through Coquitlam Lake and the dam, for the purposes of water supply and power generation, suspended salmon spawning in the upper part of the Coquitlam River.
Split into simpler sentences: Thousands of spawning salmon originally ran through Coquitlam Lake. The dam, used for the purposes of water supply and power generation, suspended salmon spawning in the upper part of the Coquitlam River.