Scientists call a lake like this meromictic: one that never fully turns over. Most lakes mix top to bottom with the seasons, cold surface water sinking and stirring the whole column. Powell Lake cannot. The salt layer at the bottom is heavy enough to stay put permanently, and because nothing mixes down into it, nothing carries oxygen down either. That deep water is anoxic, dark, and effectively unchanged since the Pleistocene - a sample of the post-glacial Pacific held in place by nothing more complicated than density. The lake itself is enormous by coastal standards: fifty kilometres long, about 120 square kilometres of surface, an average depth of 150 metres and a maximum of 360. Six interconnected basins make up its length, and two of them hold the trapped sea.

In ʔayʔaǰuθəm, the language of the Tla'amin, the lake is θaʔyɛɬ - thaʔyɛɬ - which means, plainly and accurately, freshwater lake. The Tla'amin lived at the lake's outflow in a village called tiskʷat, and they were removed from it in the 1880s to make room for industry. The name now on the chart is thought to honour Dr. Israel Wood Powell, B.C.'s first superintendent of Indian Affairs and an architect of policies that included residential schools and the banning of the potlatch, who is also taken as the namesake of the river and the city. The city has treated him as such since at least 1946, when his daughters presented a portrait of their father to a local high school. Two names, then, for one body of water: one that describes what it is, one that commemorates an official who never lived beside it. Both are still in circulation, and the older one is not going anywhere.

The same geology that trapped the salt water made the place irresistible to engineers. A low rise of land separates the lake from the Strait of Georgia, holding the water roughly forty-six metres above the tide - a natural dam requiring almost no improvement, with a very short river running down to the sea. Construction on a hydroelectric dam began in 1910, and in 1924 the lake's surface was raised to fifty-six metres above sea level. The station was never built to light a region; it was built to run a paper mill, and to supply that mill with water. The city of Powell River grew on the rise between the two, mill below, lake above. Few industrial sites anywhere have been handed so much head and so little distance to work with.

From the water the lake still behaves exactly like the fjord it used to be. Steep forested walls climb straight from the shoreline, the basins bend out of sight from one another, and the whole thing runs deep into the Coast Mountains rather than sprawling across open ground. Goat Island, large and mountainous, sits in the middle of it, big enough to read as mainland until you come around the end and discover the water continues on the other side. The arms run north and northeast into country with no roads. The outflow at the south end is short enough that the sea is close the entire time you are on the lake, which is a strange sensation on fresh water - and a fair reminder that the ocean got here first.