Weird Harold wrote:Keith_w wrote:...For example, the Rocky mountains are a watershed from which the water on the eastern side flows to Hudson's Bay, ...
Actually, the American Rocky Mountains drain eastward into the Mississippi and/or the Gulf of Mexico. That's also true for the southern portion of the Canadian Rockies, although I don't recall off-hand how far North that's still the case.
The Bow river, which flows through Banff and Calgary ends up in Hudson's Bay.
The Bow River is a river in the Canadian province of Alberta. It begins in the Rocky Mountains and winds through the Alberta foothills onto the prairies where it meets the Oldman River, the two then forming the South Saskatchewan River. These waters ultimately flow through the Nelson River into Hudson Bay. The Bow River runs through the city of Calgary, taking in the Elbow River at the historic site of Fort Calgary near downtown. The Bow River pathway, developed along the river's banks, is considered a part of Calgary's self-image
https://en.wikipedia.org/wiki/Bow_River
The Columbia river starts not far from there and flows to the Pacific.
The Columbia River is the largest river in the Pacific Northwest region of North America.[9] The river rises in the Rocky Mountains of British Columbia, Canada. It flows northwest and then south into the US state of Washington, then turns west to form most of the border between Washington and the state of Oregon before emptying into the Pacific Ocean. The river is 1,243 miles (2,000 km) long, and its largest tributary is the Snake River. Its drainage basin is roughly the size of France and extends into seven U.S. states and a Canadian province.
https://en.wikipedia.org/wiki/Columbia_River
Be that as it may, water flows downhill and always finds it's own level. Trying to cross a watershed without additional water pumped from lower levels will certainly be a futile effort.