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DRAINAGE BASINS

 

A. INTRODUCTION

Hydrologic cycle

where does water go when it reaches the earth's surface

how does it get there?

Water in rivers & streams gets there via:

direct precipitation - quick

surface runoff (overland flow) - fairly quick

through flow - relatively slow

groundwater flow - slow

Stream flow: externally driven force; primarily helps wear the landscape down

Rivers: conduits for draining water and sediment from the continents

 Image: hydrologic cycle
Image credit: National Weather Service (2005) Jetstream: An Online
School for Weather. http://www.srh.weather.gov/srh/jetstream/atmos/hydro.htm

B. DRAINAGE BASINS  link: text note

  • Land area contributing water to a connected system of rivers & streams

Defined by topography

  • drainage divides

  • mouth or outlet: where streamflow exits the basin

  • sub-basins link: hydrosheds

Description

  • Soils

  • Vegetation

  • Landuse

  • Topography

 Diagram of a drainage basin

C. STREAM DISCHARGE

Discharge = stream flow = width x depth x velocity

Diagram: river width, depth & flow velocity

Hydrographs: graphs showing changes in discharge over time

  • annual hydrographs

Graph: annual hydrograph Grant River, WI

 

  • storm hydrographs

Graph: idealized storm hydrograph

 

  • hydrograph comparisions

Graph: idealized hydrograph comparisons

 

D. SEDIMENT LOAD

Types of Load link: text note

  • suspended load

  • bed load

  • solute load

Sources of Sediment

  • the river channel

  • land areas neighboring the river channel

 photo: muddy water near Mt.St. Helens

Factors Affecting Amount of Sediment

diagram: water discharge from the Mississippi River
Image credit: Meade, R.H. (1995) Contaminants in the Mississippi River, USGS Circular 1133. http://pubs.usgs.gov/circ/circ1133/geosetting.html		 diagram: sediment discharge from the Mississippi River
Image credit: Meade, R.H. (1995) Contaminants in the Mississippi River, USGS Circular 1133. http://pubs.usgs.gov/circ/circ1133/geosetting.html

photos: Mississippi, Yangtze & Pearl River deltas
Image credit: SeaWiFs, NASA Goddard Space Flight Center, Ocean Color http://daac.gsfc.nasa.gov/oceancolor/scifocus/oceanColor/dead_zones.shtml

E. SUMMARY

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© Karen A. Lemke: klemke@uwsp.edu
Last revised April 23, 2007