Surface Water
Chapter 9
Surface water movement: Water Cycle
Earths water supply is constantly recycled
Surface Water Movement
1) Runoff
Water flowing down slope along Earth’s surface or
seep into the ground
 Run off speed determined by slope of the hill
Ends up in a stream or lake, evaporate, or
accumulate into puddles
Movement
Seep into ground
Ground must have large enough pores – loose
soil
Evaporate
Fate of water: Run off or Seep
 Certain characteristics will determine whether
not water will either seep into or become runoff
1) Vegetation
Vegetation allows for loose soil
 Loose soil allows water to enter ground
 Gardeners do not pack their soil
Fate of water
2) Rate of precipitation
Heavy:
soil clumps together closing pores
Fills up ground to quickly and water becomes runoff
Light:
allows water to gently slide through
Less erosion
Fate of Water
3) Soil Composition
Effects the waters holding capacity
Decayed organic matter (humus)
Creates the pores in soil – Increases retain ability
Minerals
Clay – fine mineral which clump together
• Few Spaces
Sand – large pores
Fate of Water
4) Slopes
Steep: allows for high runoff & little absorption
Little: low runoff and high absorption
Formation of Stream systems
Runoff
Surface water flows in thin sheets and
eventually collects in small channels
Runoff increases, channels widen and
become deeper and longer
Channels fill up again each time with rain
Channel can become a stream
Water sheds:
drainage basin
Land where all water drains into
Divide
High land area that separates watersheds
Mississippi Watershed
Stream Load
All the materials that the stream carries
Solution
Material that has been dissolved
Depends on area where the steam runs through
Erosion of rocks and dirt
Stream Load
Suspension
Small particles held up by the turbulence of stream
Clay, silt, sand
Depends on volume and velocity of water
Bed Load
Turbulence of water pushes heavy things
Pebbles and cobbles
Larger velocity – large objects
B/c of abrasion, rocks are smooth
Stream Velocity & Carrying Capacity
Discharge = width x depth x velocity
(m)
(m)
(m/s)
As discharge increases so does carrying
capacity
Floods
Water fills over the sides of a stream banks
Floodplain: broad flat area of land that
extends out from streams for excess flooding