Geography 101 logo | Geog 101 Home | Calendar | Syllabus | Study Aids | Evaluation & Grading | Geog/Geol Dept | UWSP |

    DRAINAGE BASINS

A. INTRODUCTION

Hydrologic cycle

  • where does water go once reaching 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

Rivers

  • conduits for draining water & sediment from continents

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

 Diagram: 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: textbook note

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

Defined by topography

  • drainage divides

  • mouth (outlet): where stream flow exits basin

  • sub-basins Link: hydrosheds

Description

  • soils

  • vegetation

  • landuse

  • topography

 Diagram: drainage basin

C. STREAM DISCHARGE

Discharge = stream flow = width x depth x velocity

Diagram: river width, depth & flow velocity

Hydrograph:

  • annual hydrograph

 Graph: annual hydrograph Grant River, WI

  • storm hydrograph

 Graph: idealized storm hydrograph

  • hydrograph comparisons

 Graph: idealized hydrograph comparisons

 

D. SEDIMENT LOAD

Types of Load Link: textbook note

  • suspended load

  • bed load

  • solute load

Sources of Sediment

  • the river channel

  • land area neighboring the river channel

 Photo: river with high sediment load

Factors Affecting Amount of Sediment

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

| Review Questions | Next Lecture | Previous Lecture | Calendar | Geog 101 Home |
©Karen A. Lemke: klemke@uwsp.edu
Last revised November 29, 2008