- Columbia County, Washington (Wikipedia)
Columbia County is a county located in the U.S. state of Washington. As of the 2020 census, the population was 3,952, making it the second-least populous county in Washington. The county seat and largest city is Dayton. The county was created out of Walla Walla County on November 11, 1875, and is named after the Columbia River (which does not flow through the county). Columbia County is included in the Walla Walla, WA Metropolitan Statistical Area.
- Drainage basin (Wikipedia)
A drainage basin is an area of land where all flowing surface water converges to a single point, such as a river mouth, or flows into another body of water, such as a lake or ocean. A basin is separated from adjacent basins by a perimeter, the drainage divide, made up of a succession of elevated features, such as ridges and hills. A basin may consist of smaller basins that merge at river confluences, forming a hierarchical pattern.