Full topic notes for : ROCKS AND WEATHERING, ATMOSPHERE AND WEATHER AND RIVERS ( HYRDOLOGY AND FLUVIAL GEOMORPHOLOGY)
These notes were used by 15 students the majority of which got high A Grades ( No A* possible). They were written by an A* Predicted Student for AS Exams.
PHYSICAL MODULES ENTIRE AS:
ROCKS AND WEATHERING,
ATMOSPHERE AND WEATHER AND
RIVERS ( HYRDOLOGY AND FLUVIAL
GEOMORPHOLOGY)
AS Notes CIE Entire Physical Year 1
CIE
[Email address]
,AS Geography Notes-
Hydrology and Geomorphology
Hydrology-is the study of the distribution and movement of water within the atmosphere at
under and on the earth’s surface.
Hydrological cycle-involves the recycling of water through the earth and atmosphere.
The drainage basin hydrological cycle
The river basin is part of the cycle, rivers
operate at the local drainage basin scale DB.
Drainage basin-An area of land within which
water collects and is drained by a river system.
DB is an open system, compromising of inputs,
stores, transfers and outputs.
Inputs-Water entering the drainage basin via
precipitation.
Stores-Water which is held within the
drainage basin, temporarily on leaves and
more permanently in the ground.
Transfers-Flows-moving of water from one
location to another e.g. Base-flow,
groundwater flow, infiltration and
percolation.
Outputs-Where water leaves the drainage
basin e.g. evaporation, transpiration, also via
rivers as it exits.
- Precipitation: All forms of rainfall, snow, frost, hail and dew. It is the transfer of moisture in
the atmosphere to the land through the processes.
- Interbasin flow: Surface or groundwater flow between two drainage basins.
- Evaporation: The loss of water from the land surface and bodies of water as it transfers
from a liquid to a gaseous state by application of heat.
- Transpiration: The loss of water vapour from the stomata in the leaves of plants and trees.
- Evapotranspiration: The combined loss of water from evaporation and transpiration.
- Run-off: The flow of water over the surface of the earth.
- Throughfall: Precipitation which falls straight through the vegetation cover without being
intercepted and reaches the ground. It may be initially intercepted and then drip down from
the leaves in a process known as ‘drip flow’.
- Stemflow: The flow of intercepted precipitation down the stems of plants to reach the
ground.
- Potential evaporation or potential evapotranspiration is defined as the amount of
evaporation that would occur if a sufficient water source were available
- Overland flow: The flow of water over the surface of the earth. (see later).
- Infiltration: The process by which water soaks into or is absorbed by the soil.
- Percolation: The movement of infiltrated water soaking through the soil, creating
groundwater storage.
Overland flow consists of-
,AS Geography Notes-
Channel Flow- The flow of water through rills, streams or river channels.
Sheet flow-The flow of water over the surface in a sheet or layer occurs when either the
infiltration capacity of the ground has been met or the surface is impermeable.
Hortonian Overland Flow-The overland flow caused when the percolation/infiltration rate is
exceeded by the rate of rainfall, causing large volumes of water to flow in streams on the
surface.
- Saturation Overland Flow- When the groundwater table sits at the surface and all the
pores and gaps in the underlying soil and rock are filled with water, thus preventing any
more infiltration, the overland flow is known as saturation overland flow.
- Capillary Action: The flow of water through tight spaces without the assistance of gravity
and other external forces.
- Throughflow: The downslope and lateral flow of water through the soil.
- Baseflow: The slow, lateral movement of water through the underlying geology under
gravity or hydrostatic pressure through cracks and joints beneath the water table.
Definitions-
Watershed-The Boundary or divide between drainage basins what he says maybe obvious
arteries or unclear (boggy upland areas) they determine where the water flows into one
drainage basin or an adjacent one.
Confluence-Where two smaller streams join or a tributary meets the river channel.
Tributary-Smaller streams feeding into the main river.
Source-Where the rivers begin usually boggy upland areas.
Mouth-Where the river meets the sea
Permanent Streams-Streams which are always flowing
Ephemeral Streams-Flood streams or storm streams which flow under heavy rainfall
conditions.
, AS Geography Notes-
Drainage Basin Exam Diagram
Drainage Basins-
Physical characteristics
Basin size
This influences the lag time – a large drainage basin will mean that water takes a long time to
travel through tributaries or the ground to reach the channel.
Conversely, a small drainage basin means that water has a shorter distance to travel and will
result in a shorter lag time.
Basin shape
Circular drainage basins mean that all points on the watershed are equidistant from the
channel and this will lead to a shorter lag time and higher peak discharge.
Elongated drainage basins are characterised by longer lag times and lower peak discharge as
the water drains from the furthest reaches of the watershed to the channel. Drainage basins
that are more circular in shape lead to shorter lag times and a higher peak discharge than
those that are long and thin because water has a shorter distance to travel to reach a river.
A perocline is a line of concentrated water flow. Pipe Flow is the rapid movement of water
in subterranean channels, roots, earthworm or animal holes. Aquiclude is An impermeable
body of rock or stratum of sediment that acts as a barrier to the flow of water, aquitard is
a zone within the Earth that restricts the flow of groundwater from one aquifer to another.
A completely impermeable aquitard is called an aquiclude or aquifuge. Aquitards comprise
layers of either clay or non-porous rock with low hydraulic conductivity. which is a zone
within the ground which restricts GW flow from one aquifer to another. Aquifer is a
permeable rock that can store water. Phreatic zone area below the water table where rocks
are permanently saturated. Water table Upper limit of permanent saturation.
Porosity-Capacity of a rock to hold water is a measurement of total void space in %. E.g.
How much rock is open space depends on the rock type, shape. Most rock 1-40%, most
sedimentary rocks e.g. Sandstone, limestone.8% porosity 92% solid. Clay soils are porous
40%-70%.
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