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Water-Rivers
Whenever the amounts of percipitation is in
excess of the Sum of evaporation,penetration
and crater collections capacity,the excess
waters after formation of a layer or thin
layers over the ground surface,will cause a
surface flow which could have the potential
of starting a river.
The water currents often flow either
permanently or temporarily.Temporary flows
are due to torrential showers and flooding.
These currents,unlike the normal river ones,
don't have any established path,instead they
extend over the surface and create a flat
current.
Rivers are classified into three categories
based on their water resources :
rivers that are supplied by , 1 - thawing of snow ,
2 - rainwaters , and 3 - both.
In general every permanent and temporary
current has its distinctive shape.At the
source of the flow many small streams of
water join each other at the foot of the
elevations . The surface formed by these
flowing streams resemble a cone with the
base facing the peak and the vertex pointing
towards the slope of the mountains.The sum
of these primary cones which form even
a bigger cone in the mountains is called
the " basin reception point ".Small currents
join into larger ones which follow in defined
tracks in a valley.This valley is called
water way.As these waterways encounter flat
surfaces , they spread into cones with the
vertex pointing towards the waterway and the
base facing depression and seas.
The more or less deep,long and branching
crevices that have been hollowed out in soft
soil which is not compact by these rivers
are called " gullies " or " ravines ".The
intersection of river with sea is called
the mouth.Many rivers bring with themselves
sediments to the mouth and slowly form
an area the shape of " Delta " whose vertex
is towards the river and is called " Delta ".
A river that reaches a sea is called
" exodoreism " and one which flows into
lagoons or lakes is known as " endodoreism ".
Rivers often assume spiral shape over flat
and alluvium lands which is the result of
differential pressure within the two
riverbanks.Sometimes these spirals recede and
slowly form complete loops which are called
Meander. Some other times during over flows
the river may follow a straight path
cutting off the loop and maintain the path up
to the end of the overflow.In this situation
a false river will eventually form a lagoon
and then disappear.Normally,river water often
flows in a small and narrow bed which is
called " the minor bed ". During overflows
the water level will increase to above the
minor bed,cover its upper lands,and continue
to flow in a wider bed called " the major
bed " . Often in mountaineous regions
an otherwise calm river will change in to
a fast moving and roaring one called
" rapides ". Waterfalls are also another
phenomenon sometimes found in the path of
the rivers.The reason for this phenomenon
is the extension of hard bedrocks in a more
or less tall stair fashion in the bed.The
most important waterfalls in the world are
" Niagara falls " in North America and
" Victoria falls " in South Africa. Rivers
often flow in an orderly fashion and in
a downward slope from the highlands these
to seashores and are called " consequent ".
Sometimes the rivers change direction near
the shore and run parallel to it . This
phenomenon is called " subsequent " flow.
Flow of each river goes through three stages
in its life time : youth,maturity and aged.
During the youth period rivers exhibit severe
destruction activities and often due to great
elevation differentials , higher velocities,
waterfalls and craters will form.In maturity,
the rivers reach an equilibrium with slower
flow and minimum destruction.In old age large
elevations disappear and the riverbed and
surrounding area become almost flat.These
periods are mostly theoretic and there are
several other factors which maintain the
flow in youth and maturity stages.
