Water 1: Processes

Water: Celebrated Throughout History

"When the well is dry, you know the value of water.” -Benjamin Franklin

Water, water, everywhere,And all the boards did shrink.Water, water everywhere,Nor any drop to drink.-Samuel Taylor Coleridge (1772-1834), "The Rime of the Ancient Mariner" 1798  

"Whiskey is for drinking; water is for fighting over."- Attributed to Mark Twain

Water Cycle– Abundance is not a problem– Distribution and time of

occurrence are the problems; needs to be in the right place at the right time

– As water moves from one reservoir to another, it carries sediment, chemicals, waste, nutrients, etc.

– 1 is balanced by 2 & 3– 3 is balanced by 6– 3 & 4 are balanced by 5– 60% of terrestrial precip

evaporates (4), whereas 40% returns to ocean (6)

World’s Water Supply

Location Percent Residence Time

Oceans 97.2 103 years

Ice caps and glaciers 2.15 105+ years

Shallow groundwater

0.31 102-103 years

Lakes 0.009 10 years

Atmosphere 0.001 9 days

Streams 0.0001 2 weeks

Source: U.S.G.S.

Water: Unique Liquid (H-O-H)

• General Properties– Covalently bonded – electron

sharing– Dipolar – charge distribution

leads to …– Cohesion vs. adhesion

(hydration of clay particles)– Triple point on phase

diagram (s-l-v) – transfers easily between water cycle reservoirs on Earth

– Specific heat – great capacity to store and absorb heat

– Only common substance with a solid form lighter than its liquid form – why ice floats

Surface Runoff and Sediment Yield

• Effect of underlying geology (rock type) on surface run-off within a watershed or drainage basin

• Large drainage basins are divided into smaller basins

• Rain falling on either side of a divide may end up in very different places

Drainage Basins of the World

Factors Affecting Runoff

– Geologic factors (drainage density)– Physiographic factors

• Basin shape• Relief and slope• Orientation of stream basin

– Climatic factors• Timing and magnitude of precipitation

– Biologic factors• Vegetation – interception/transpiration efficiency• Animals – burrowing/grazing• Soil organisms – opening of macropores to

enhance infiltration capacity of landscape

Surface Runoff

Runoff Paths– Throughflow – shallow subsurface flow above water table– Overland flow – when precip. Intensity exceeds infiltration

capacity– Groundwater flow – movement through the saturated zone

Sediment Yield

River Sediment Load (t/km2)

Amazon 63

Mississippi 97

Nile 37

Missouri 159

Yangtze 257

Colorado 212

Lo 7,300