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Understanding Drainage Basins as Open Systems: Processes and Physical Factors, Lecture notes of Humanities

The concept of drainage basins as open systems, focusing on the system processes and the influence of physical factors such as relief, geology, soil, vegetation cover, and climate. Students are encouraged to discuss the impact of each factor on the drainage basin system and complete related tasks.

Typology: Lecture notes

2021/2022

Uploaded on 09/27/2022

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QU:Howdodrainagebasinsoperateasopensystems?
AIM:
Todescribethesystemprocessesofdrainagebasinsandexplainhow
physicalfactorscaninfluencethese.
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Watershed
ST:Usingtheimagedefinewhatyouthinkismeantbyadrainagebasin.
DrainagebasinTheareaoflanddrainedbyaparticularriverandstreamnetwork.Itisan
opensystemofinputs,processesandoutputs.
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Download Understanding Drainage Basins as Open Systems: Processes and Physical Factors and more Lecture notes Humanities in PDF only on Docsity!

QU: How do drainage basins operate as open systems?

AIM: To^ describe^ the^ system^ processes^ of^ drainage^ basins^ and^ explain^ how

physical factors can influence these.

1 2 3

Watershed

ST: Using the image define what you think is meant^ by^ a^ drainage^ basin.

Drainage basin The area of land drained by a particular river and stream network. It is an

open system of inputs, processes and outputs.

Watershed Drainage basins are local open systems. A drainage basin is an area of land drained by a river and its tributaries (river system). It includes water found in the water table and surface runoff. There is an imaginary line separating drainage

basins called a

watershed. Usually, this

is a ridge of high land.

The black line in Figure

1 shows the watershed

for the Bath Avon river

basin. Any precipitation

that falls on the other

side of the watershed

will flow into a river in

the adjacent river basin.

Thames basin Fig 1 EXT: What is significant about this line for flood prevention planners in Bath?

  • Using^ sheet^ 14,^ complete^ the^ diagram^ 'Drainage Basin and Hydrological Cycle' Shade inputs, outputs, stores and fluxes in different colours. Define terms you do not understand in your notes.

Missing terms for sheet 14 'Hydrology and Rivers'

Interception Stemflow Soil Precipitation x 2 Infiltration x 2 Bedrock Watertable Groundwater flow Evaporation^ Surface^ runoff Channel catch Deep percolation Transpiration River Throughflow Fossil water Create a key and shade the input, fluxes, stores and output boxes on your diagram. Drainage basins are localised elements of the Global Hydrological Cycle which is a closed system. They are part of the process in which water returns to the sea under the influence of gravitational potential energy. Drainage basins however are 'open systems' which means that inputs are not governed by outputs. In short, inputs and outputs are not always in equilibrium. TASK: The Drainage Basin System

EXT: Referring to named inputs, processes and outputs, outline why

drainge basins are an open system.

Precipitation Precipitation Interception Transpiration Infiltration Infiltration Soil Bedrock Watertable Fossil water Ground water Groundwater flow Throughflow Stem Flow Evaporation Channel catch Surface Runoff River

Physical factors can affect the processes in a drainage basin greatly. In pairs

discuss how each factor on the mind map provided can effect the drainage basin

system. You must address the questions posed below for each factor. NAME the

inputs/flows/stores/outputs you refer to.

Relief What rainfall patterns can highland create? Impact on inputs? How quickly does steep/flat land drain? Impacts on flows/stores? Geology What differences does permeability of the rock have on stores, flows and outputs? Soil Sandy/peaty/clay? What differences would this make to flows, stores and outputs Vegetation cover How can this influence inputs? Does it have any seasonal variation? Is there a link with soil and climate? Impact on flows/outputs? Climate How does this influence inputs? Which climates promote a high/low level of input? How can temperature alter flows and outputs?

EXT: What physical conditions would create a drainage basin system of fast

flows and high outputs?

What physical conditions would promote high storage and low output

conditions?

Physical factors within drainage basins determine the relative importance of inputs, flows and outputs. RELIEF VEGETATION SOIL TYPE/DEPTH (^) CLIMATE

GEOLOGY

Homework/resource/reading slides

Types of rainfall

Rainfall is the sole major input into drainage basin systems and is formed in

three main ways. Different places of the world are more subject than others

to these differing types of rainfall and this can influence the drainage basin

system. As you will note below you need to be familiar with these types of

rainfall and we did not cover it in lesson.

H/W 1 Produce 3 annotated diagrams of Frontal, Orographic (relief) and

convectional rainfall. Make sure you fully explain how rain is created as you do so.

You should be using appropriate terminology!

Also say in what regions they tend to occur and times of year/day. The web site

is helpful as is the online copy of the lesson.

https://www.quora.com/Whatarethetypesofrainfall

2 Explain how physical factors have led to contrasts in the hydrological cycles

as shown below. (6)

Convectional rainfall Very common in areas where the ground is heated by the hot sun, such as the Tropics. This is why those areas experience heavy rainfalls most afternoons. The United Kingdom does experience some convectional rainfall during the summer, particularly in the South East of the country. Convectional rainfall occurs when: The surface of the earth is heated by the sun. The warm surface heats the air above it. Hot air always rises so this newly heated air does so. As it rises the aircools and begins to condensate. Further rising and cooling causes a large amount of condensation to occur and rain is formed. Convection tends to produce towering cumulonimbus clouds, which produce heavy rain and possible thunder and lightning.

Turbulence in the atmosphere and surface obstructions such as hills and mountains provide the initial upward push for the air. This rainfall occurs throughout the year near the equator daily in the afternoon. In middle latitudes, convectional rainfall occurs in early summer, in continental interiors. Cyclonic/Frontal rainfall: This type of precipitation associated with a cyclonic activity and occurs along the frontal zone (front is a narrow zone of transition, dividing two air masses of differing temperature and humidity characteristics, intersecting the earth's surface. Fronts are most clearly developed in areas where are masses converge) of convergence particularly at the ITCZ (inter tropical convergent zone) and at the polar fronts. In a zone of horizontal wind divergence, the warm air forced up over the colder air. In this slow ascend pressure decreases, air expands and cools, condensation and cooling produce a precipitation. These fronts and associated weather phenomenon are best developed in the middle latitudes, most of the winter precipitation of low lands in the middle latitudes is cyclonic or frontal is origin.

Ideal condition for heavy orographic rainfall is a high relatively continuous mountain frontier

(boundary) close to the coast and the winds from off a warm ocean meet the barrier at right angles.

This is exactly the case with western Ghats in India, which lies athwart (perpendicular) the south

west monsoon.

Orographic/Relief rainfall: It occurs when large mass of air is forced to rise across landform

barriers, such as high mountain ranges, plateau, escarpment, or over high hills. the leeward side of

such mountain barrier where the air is ascending and warming are characteristically drier are called

rain shadow region. It's most common on the windward slopes of the mountain where the onshore

moisture ladenwinds come from sea.

Condenses

Relief rainfall This is also called orographic rainfall, which is very common in the United Kingdom, especially on the West coast since the prevailing weather comes from that direction. Relief Rainfall occurs when: The prevailing winds pick up moisture from the sea as they travel across it, making the air moist. The moist air reaches the coast and is forced to rise over mountains and hills. This forces the air to cool and condense, forming clouds. The air continues to be forced over the mountains and so it drops its moisture as relief rain. Once over the top of the mountain the air will usually drop down the other side, warming as it does so. This means it has a greater ability to carry water moisture and so there is little rain on the far side of the mountain. This area is called the rain shadow.