Hydrologic Cycle – complex system,
variable in time & space over the planet,
not always complete.
(Water covers 70-71% of earth’s surface.)
EARTH’s WATER
Oceans
97.6%
Ice Caps & Glaciers
1.9%
-------Over 99% of earth’s water-------
If the all water in the atmosphere condensed, it
Ground & Soil Water
would result in 1 inch of precipitation.
0.5%
Rivers & Lakes
Atmosphere
0.02%
0.0001%
Worldwide average = 39 inches per year
Zone of Saturation- where all
Inter-particle spaces are filled
with water.
Ground Water- accumulation of
gravity water in the subsoil & bedrock,
varies geographically because of climate,
topography, and subsurface geology.
Hydraulic Gradients- ground water slowly
flows because of the water tables sloping nature.
Water Table- boundary between the soil
water & ground water zones. In coursegrained materials & clearly defined.
+ Capillary Fringe – fine-grained materials,
a transition zone ranging from a few
centimeters to several meters.
Aquifer- porous material with a heavy ground water concentration, usually sand & gravel.
Aquiclude- an impermeable underground formation.
Hydrostatic Pressure- pressure effecting the lower part of an aquifer due to the above weight of
the water.
Artesian Flow- pressurized outflow of ground water dur to hydrostatic pressure, involves a tilted
aquifer.
Pressure Surface- level to which ground water will flow by artesian means, without pumping.
Transmission- the movement of water through material.
Artesian Well- flowing or non-flowing depending on surface pressure, to maintain equilibrium
the withdraw and transmission cannot exceed the rate of recharge.
Cone of Depression- funnel-shaped depression,
Caused from water being pumped from an aquifer
at a rate greater than the aquifer’s transmissivity.
Leachates- organic & inorganic substances in a
solution, leached downward into ground water.
Runoff- movement of water over the surface of the land
(
Runoff = Precipitation - Evaporation & Transpiration ± Change in storage water
)
Drainage Basin- (Watershed or Catchment) area of land that contributes runoff into a specific
river or drainage system.
Drainage Divide- a topographic boundary that partitions runoff into different basins.
Nesting – watersheds that are made up of smaller basins,
Each one is made up of smaller ones, ect.
Tributary – a stream which feeds a larger stream.
Discharge- rate of water flow, measured by the volume of
water passing a giving point of a stream.
Long Profile- cross-section of an entire course of a stream. (along its length)
Graded Profile- smoothed, long profile that is constantly adjusting because of its response to
discharge & sediment load.
Base Level- lowest elevation a river can downcut its channel, usually controlled by sea level or
the mainstream or lakes graded profile.
+ All streams actively cause EROSION, TRANSPORTATION, and DEPOSITION
Erosion- progressive removal of mineral material from the floor & sides of the stream channel.
Hydraulic Action- force of flowing water, dragging action upon material on the stream bed.
Abrasion – (scouring) mechanical wear due to chipping, grinding, and crushing by rocks in
the current.
Solution – (corrosion) the chemical processes of rock weathering.
DEGRADATION – “high discharge” down-cutting of a stream channel.
Transportation- movement of eroded particles by the stream.
LOAD- the amount of material being transported by the stream.
Solution Load - dissolved material
Suspended Load – clay & silt held in the water turbulence
Bed Load – sand & larger moving along the channel floor
Deposition-progressive accumulation of transported particles upon the stream bed & flood plain.
AGGRADATION – “low discharge” filling in of a stream channel.
CAPACITY- maximum load a stream can carry.
LOAD
<
CAPACITY
=
EROSION (DEGRADATION)
LOAD
=
CAPACITY
=
EQUILIBRIUM
LOAD
>
CAPACITY
=
DEPOSITION (AGGRADATION)
______________________________________________________________________________
Oxbow (bayou)-small lake formed by
a cut-off loop of a meandering river.
Meander Scars-oxbows which evolved through
a swamp stage, become filled into solid land.
Natural Levees-mounds of sediments deposited along the bank by flood waters.
Terraces-elevated parts of a floodplain from when a river downcuts and establishes a new
floodplain.
Yazoo Stream- a tributary which flows generally parallel to the main river, may even be below
the main river’s elevation.
Delta- accumulation of deposits developed when a stream flows into a body of standing water.
(Bottom-Set Beds – Heavy Clays & Muds, Foreset Beds – Fine Sands & Silts, Top-Set Beds Heavy material.)
+ DISTRIBUTARIES – formed similarly to braided streams.
WILLIAM MORRIS DAVIS – proposed a series of development stages of landscape evolution as
rivers deepen and widen their valleys.
STRESSED – structure, process, and time
INITIAL STAGE – falls, rapids, ponds
YOUTH STAGE – deepened channel, drained lakes “smoothened falls”
MATURE STAGE – equilibrium, stream energy directed laterally, “meandering”
EARLY MATURE – bank cutting
FULLY MATURE – “old age” floodplain > meander belt
Rejuvenation-increase in the potential energy for the stream, base level lowering or land rising.
+ ENTRENCHED MEANDERS –
rejuvenation occurs after manturity,
gorge develops may do so in a
meander pattern.
Stream Types
Braided Stream
Single-Thread (Channel)
(1. – Sinuousity & 2. - Meandering)
(Fluctuating Discharge)
Meandering Current
DRAINAGE DENSITY (D=L/A)
-
Represents the extent of channelization
(D) = Drainage
(L) = Total length of all channels
(A) = Area of the drainage basin
Stream Order
1st Order – stream that has NO tributaries, headwaters
2nd Order – two 1st Order streams must meet
3rd Order – intersection of two 2nd Order streams
Ect.
DRAINAGE PATTERNS
DENDRITIC PATTERN
TRELLIS PATTERN
Where rocks have uniform resistance
Indicates parallel valleys of weak rock
to weathering & erosion.
between ridges of resistant rock.
RADIAL PATTERN
CENTRIPETAL PATTERN
Multiple channels trending away from
Multiple channels flowing inward toward
the top of a domed upland or volcano.
the center of a structural lowland or basin.
RECTANGULAR PATTERN
DERANGED PATTERN
Linear joint patterns in the bed rock surface.
The retreat of continental ice sheets,
characterized by a chaotic arrangement of
channels connecting small lakes & marshes.