Drainage Basins and Systems

Drainage Basins

• A drainage basin is an area of land where precipitation, springs, or flow collects and drains into a common body of water (e.g., river, lake, ocean). Also called watersheds or catchments.
• Drainage basins vary in size, from small areas collecting rainwater to large areas with many rivers.
• Higher land surrounding a basin directs water downhill into the waterway.
• The ultimate outlet can be a river, lake, wetland, bay, or ocean.

Drainage Basin Systems

• A drainage basin system is composed of smaller water basins.
• Small areas drain water into a common body of water with a common outlet, forming small water basins.
• Tributaries feed into larger rivers, and smaller watersheds are part of larger systems.
• For example, the Republican River basin collects water from the midwestern plains, and is part of the larger Missouri River and Mississippi River basins.

Basin in Geography

• A basin is a circular or oval-shaped depression in the Earth's surface.
• Basins can be formed by erosion or other forces and can be dry or contain water.
• The sides of a basin are higher than the bottom.
• Examples of basins include the Republican River basin.

Drainage Divides

• Drainage divides are high ground areas that separate drainage basin systems.
• Divides can be mountain ranges or ridges.
• Precipitation on a divide flows into only one basin.

Watershed Characteristics

• Watersheds are drainage basins (land surrounded by higher land ridges) through which both surface and groundwater flows.
• Watershed characteristics can vary greatly.
• May have steep or gentle slopes.
• Drainage areas can be large and flat, or narrow and steep.
• Human activity affects and is affected by watershed characteristics.

Formation of Drainage Basins and River Systems

• Drainage basins and river systems form due to gravity-induced water flow (precipitation, springs).
• River systems start with runoff (water flowing across the land).
• Small watersheds (from a rill) become part of larger drainage basins.
• A first-order stream forms when runoff and springs combine and flow at least 90% of the time.
• First-order streams are small, fast-moving, and have no tributaries.
• When first-order streams merge, they form higher-order streams (second-order, etc.).
• River systems and their drainage areas grow with the merging of smaller ones into larger ones.
• Scientists use a 12-order stream classification system. (Mississippi 10-11th order, Amazon 12th order).

Drainage Basin Examples

• All rivers originate from a watershed or drainage basin.
• Large basins are made up of numerous smaller basins.
• Examples include the Mississippi River basin (one of the largest globally).
• The Mississippi River basin drains 1.2 million square miles in the central United States.
• The basin includes many tributaries – Missouri, Ohio, Arkansas.
• These tributaries have their own watersheds.
• The Mississippi River's common outlet is the Gulf of Mexico.
• Rocky Mountains and Appalachian Mountains form western and eastern drainage divide boundaries, respectively.

Explore the fascinating concepts of drainage basins and basin systems in geography. This quiz covers the definitions, sizes, and functions of drainage basins, as well as their roles in larger water systems. Test your knowledge on how water from various sources flows into common outlets.