# Drainage basin A **drainage basin** (watershed, catchment) is an area of land that drains all its streams and rainfall to a common outlet, such as the mouth of a river, a reservoir or any point along a stream; the ridges and hills that separate basins are drainage divides.[^usgs-ws] Larger basins contain many smaller ones, and the streamflow and water quality at an outlet reflect everything happening on the land above it.[^usgs-ws] The Mississippi River's basin covers about 40% of the United States.[^theis-water] Minnesota sits where three continental basins meet: at the Hill of Three Waters near Hibbing, water divides between Hudson Bay, the Gulf of St. Lawrence and the Gulf of Mexico.[^hmdb-3waters] <div class="microsim-player"> <iframe src="https://wikitube-3d-microsims.netlify.app/Drainage_basin.html" width="100%" height="620" frameborder="0" loading="lazy" sandbox="allow-scripts allow-same-origin" allow="accelerometer; gyroscope" title="Drainage basin — p5.js microsim"></iframe> </div> *Microsim (THY-111): rain on a landscape with three outlets named for Minnesota's drainages; every drop follows the steepest way down, and tilting the land moves the divides. ILLUSTRATIVE: a synthetic landscape, not a map.* Videos: [16:9](https://wikitube-3d-microsims.netlify.app/media/Drainage_basin_16x9.mp4) · [9:16](https://wikitube-3d-microsims.netlify.app/media/Drainage_basin_9x16.mp4) ## Major drainage basins of the world Continental divides separate the land into basins draining to different oceans, and within them great river basins such as the Mississippi's collect water from many states or countries.[^theis-water] ### Ocean basins Land can be grouped by the ocean its water reaches. North America's drainage divides split water among the Atlantic, the Arctic via Hudson Bay, the Gulf of Mexico and the Pacific; in Minnesota three of these meet.[^hmdb-3waters][^dnr-water] ### Largest river basins The Mississippi River drainage basin includes about 40% of the United States, including smaller basins such as the Ohio and Missouri.[^theis-water] ### Endorheic drainage basins Some basins have no outlet to the sea; their water leaves only by evaporation or seepage, and their terminal lakes are often salty. ## Importance Because a basin gathers everything that falls on it, it is the natural unit for managing water, floods and pollution.[^usgs-ws] ### Geopolitical boundaries Rivers that cross borders make basins shared resources; disputes have arisen over the Colorado, Nile, Euphrates, Ganges and Jordan rivers.[^theis-water] ### Hydrology In [[Hydrology|hydrology]] the basin sets the area over which rain is collected: one inch of rain on a one-square-mile watershed amounts to about 17.4 million gallons that would reach the outlet if none evaporated or soaked in.[^usgs-ws] ### Geomorphology Rivers erode soil and dissolve minerals as they carry water downhill, so the basin also sets the sediment and dissolved load a river delivers.[^theis-water] ### Resource management Watershed management coordinates land use, water supply, flood control and water quality across the whole area that drains to a point.[^usgs-ws] ## Catchment factors How a basin responds to rain depends on its topography, shape, size, soils and land use. ### Topography Relief sets where the divides lie and how fast water runs off; every drop follows the steepest way down. ### Shape Compact, round basins deliver runoff from all parts to the outlet at about the same time and have sharper flood peaks than long, narrow ones. ### Size Larger basins collect more water but take longer to deliver it, so their floods rise and fall more slowly. ### Soil type Permeable soils absorb more rain and feed groundwater; clay soils shed more as runoff.[^usgs-infil] ### Land use Impervious surfaces speed runoff and reduce infiltration, raising flood peaks.[^usgs-infil][^epa-urban] ## Minnesota *This section is specific to Wikitube.* At the Hill of Three Waters, at the Hull-Rust Mahoning Mine near Hibbing, two continental divides meet: from there water flows north to Hudson Bay, east to the Gulf of St. Lawrence and south to the Gulf of Mexico.[^hmdb-3waters] The [[Red_River_of_the_North|Red River of the North]] carries water north toward Hudson Bay, [[Lake_Superior|Lake Superior]] east to the St. Lawrence, and the [[Mississippi_River|Mississippi]], which runs 680 miles within the state, south to the Gulf.[^dnr-water] Wikitube keeps one page for each: [[WT!Minnesota_Hudson_Bay_Basin]], [[WT!Minnesota_Great_Lakes_Basin]] and [[WT!Minnesota_Gulf_of_Mexico_Basin]]. ## See also - [[Hydrology]] - [[Water_cycle]] - [[Hydrograph]] - [[Mississippi_River]] ## References [^usgs-ws]: U.S. Geological Survey, Water Science School. "Watersheds and Drainage Basins." https://www.usgs.gov/water-science-school/science/watersheds-and-drainage-basins [^theis-water]: Theis, Tom; Tomkin, Jonathan, eds. (2015). *Sustainability: A Comprehensive Foundation*, ch. 7, module "Water Cycle and Fresh Water Supply." https://open.umn.edu/opentextbooks/textbooks/sustainability-a-comprehensive-foundation [^hmdb-3waters]: Historical Marker Database. "Hill of Three Waters or the Triple Divide." https://www.hmdb.org/m.asp?m=27715 [^dnr-water]: Minnesota Department of Natural Resources. "Lakes, rivers, and wetlands facts." https://www.dnr.state.mn.us/faq/mnfacts/water.html [^usgs-infil]: U.S. Geological Survey, Water Science School. "Infiltration and the Water Cycle." https://www.usgs.gov/water-science-school/science/infiltration-and-water-cycle [^epa-urban]: U.S. Environmental Protection Agency, CADDIS. "Urbanization – Hydrology." https://www.epa.gov/caddis/urbanization-hydrology ### Portal Books - Theis, Tom; Tomkin, Jonathan, eds. (2015). *Sustainability: A Comprehensive Foundation* — [OTL record](https://open.umn.edu/opentextbooks/textbooks/sustainability-a-comprehensive-foundation); on the [[PORTAL_Energy]] shelf. ## Wikipedia : Wikitube **Strict pair:** [Wikipedia](https://en.wikipedia.org/wiki/Drainage_basin) : [Wikitube](https://en.wikitube.io/wiki/Drainage_basin) · pinned revision [1372899159](https://en.wikipedia.org/w/index.php?oldid=1372899159) · 2026-09-10 ## Previous hub tags Hubs: `Life_Physics`, `Systems`. Portals: [[PORTAL_Thury_Hydrodynamics_Apex_Spine]], [[PORTAL_Stock_and_flow]]. --- *Thury station wave · 2026-09-10 · drafted · microsim THY-111 (p5.js) · parent [[Hydrology]].*