RIVERS


Water


The volume of water on Earth is estimated to 
be about 1.36 billion cubic kilometers with:



		97% in the oceans
		 2% in glaciers
		 l% in streams, lakes, ground 			
		water,  and the atmosphere
		

The Hydrologic Cycle



Evaporation: liquid to vapor



Transpiration: release of water vapour from 
plants



Condensation:  As water vapour rises, it cools 
and eventually condenses



Precipitation:  Rain, snow and hail



Surface runoff: Sheet wash or channels






Percolation: migration from surface down



Ground water:



Running Water



Streams modify their channels




Gradient - slope over which the stream flows




The ULTIMATE BASE LEVEL is sea level - 
streams will not erode their base below base 
level




There may be temporary base levels which 
control the behavior of segments of a stream 
- a dam, for example









Properties of Moving Water



Discharge = Width x Depth x Velocity                
measured in cubic feet/second
  


An increase in discharge will result in an              
increase in all three parameters -- unless one 
of more of the parameters has been fixed.




Streams carry sediment as part of the 
SUSPENDED LOAD or as part of the BED 
LOAD



In general, the suspended material is finer 
than the bed load and is transported faster 
than the bed load material.




As velocity changes, for example, material in 
the bed load may be suspended and 
transported with a higher velocity.





The COMPETENCY of a stream is a measure 
of the largest particle it can transport in the 
suspended load.







The CAPACITY is a measure of the total 
suspended load.


In addition, streams can carry ions in 
solution - the CHEMICAL LOAD.




Imagine constructing a dam across a river
Above the dam the river begins to deposit 
material as it adjusts to the new base level
Below the dam erosion can occur at the base 
of the dam.  A lake forms behind the dam - 
becomes a temporary base level



Environments of Deposition



The preservation potential addresses the 
likelihood that deposits will be preserved in 
the rock record.




Continental - relatively low preservaton 
potential:



	Alluvial Fans




	Fluvial (River) Systems






	Lacustrine Systems - Lakes




Transitional Systems - beaches, barrier 
islands, washover fans, etc.



Marine


	pelagic component (air fall plus material in 
	the water column)


	turbidity currents - adds a terrestrial 
	component to the deep sea sediment
	calcium carbonate compensation depth - 
	CCCD