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Freshwater – Issues and conflict

 

Water Scarcity-1600x600px

This optional theme focuses on water on the land as a scarce resource. It considers the ways in which humans respond to the challenges of managing the quantity and quality of freshwater, as well as the consequences (whether intended or unintended, positive or negative) of management. The theme includes both the physical geography of freshwater (basic hydrology and floods) and human impacts on water quality.

 

Water Dry-Earth-e1336588274798

This theme should include the study of at least one detailed case study at the drainage basin level. Reference should be made to additional examples, at a range of scales, in less depth, wherever appropriate.

Freshwater – Issues and conflict

 1 The water system

The hydrological cycle: Examine the inputs, outputs, stores and transfers of the hydrological cycle. Discuss the causes and consequences of the changing balance between water stored in oceans and ice.

The water balance: Explain the concept of maximum sustainable yield of freshwater in terms of a balance between inputs and outputs.

2 Drainage basins and flooding

Drainage basins: Examine the functioning of a drainage basin as an open system with inputs, outputs, transfers, stores and feedback loops.

Discharge: Define stream discharge. Examine its relationship to stream flow and channel shape.

Hydrographs: Describe the characteristics of a hydrograph. Examine the reasons for spatial and temporal (short-term and long-term) variations in hydrographs. Examine the role of hydrographs in forecasting the magnitude, spatial extent and timing of floods.

Floods: Discuss the natural and human causes and consequences of a specific river flood.

3 Management issues and strategies

Dams and reservoirs: Examine the hydrological changes resulting from the construction of dams and reservoirs. Examine the costs and benefits of dams and reservoirs as part of multi‑purpose schemes.

Floodplain management: Explain the stream channel processes (erosion, transport, deposition) and explain the resultant landforms found on floodplains.
Examine the human modifications of a floodplain and their effect on the size and probability of floods.
Evaluate the costs and benefits of alternative stream management strategies.

Groundwater management: Explain the functioning and management of artesian basins and aquifers, distinguishing between natural and artificial recharge. Examine the environmental impacts of groundwater abstraction.

Freshwater wetland management: Describe the role of wetlands as a water resource. Evaluate the effectiveness of the management strategies that have been adopted in a major wetland.

Irrigation and agriculture: Examine the environmental impact of agriculture and irrigation on water quality: salinization, agro‑chemical run-off, the pollution of groundwater and the eutrophication of lakes, rivers and wetlands.

4 Competing demand for water

Conflict at the local or national scale: Examine the competing demands for water in a specific river basin. Evaluate the strategies that have been adopted to meet these demands.

Conflict at the international scale: Discuss an example of an international conflict related to freshwater.

1 The water system

1.1 The hydrological cycle

Hydrological Cycle (Water Cycle): The continuous movement of water on the land, in the atmosphere and in the oceans.

The hydrological cycle is said to be a closed system because water can not be added or lost. Although water can not be added or lost it can be found in different states and in different locations. Despite the planet being covered in water, the vast majority is sea water (97.5%). Of the remaining 2.5% the majority is held in glaciers and ice sheets. Only a very small amount of the world’s water is easily accessible in rivers and lakes (0.00069%).

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1.2 The water balance

This is the balance between inputs into a drainage basin and outputs. It is important for understanding the processes operating in a drainage basin and water balances throughout the year.

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It is expressed as follows:  P = Q + E (+/- change in storage) P = precipitation Q = run-off E = evapotranspiration
The water balance basically looks at the balance between inputs and outputs. You can look at the water balance at a global level (hydrological cycle), at a local level (drainage basin cycle) or even just a field. At a global level oceans tend to experience greater outputs (evaporation) than inputs (precipitation). This is because oceans are large areas with no shade that have regular winds blowing saturated air on land, allowing greater evaporation. In addition oceans don’t tend to suffer from the same amount of relief and convectional rainfall as land does. On land, inputs (precipitation) tends to be greater than outputs (evaporation). This is because lands suffers from larger amounts of frontal, relief and convectional rainfall, as well as much of the lands water being protected underground or in shaded areas reducing evaporation. At a global level there obviously has to be an equilibrium between inputs and outputs. The excess precipitation on land is returned to the oceans by channel flow, surface run-off and to a lesser extent groundwater flow. The excess of evaporation is returned to the land from the sea by winds blowing saturated air on land.

At a more local level, the following formula is usually used to calculate the water balance:
S = P – Q – E

S = Stores and transfers
P = Precipitation
Q = River discharge
E = Evapotranspiration

2. Drainage basins and flooding

2.1 Drainage basins

Drainage basin

A drainage basin is an open system that has inputs, outputs, stores and transfers (flows).

Inputs: When water is added to a drainage basin.

Rivers rain

Precipitation: Any moisture that falls from the atmosphere. The main types of precipitation are rain, snow, sleet, hail, fog and dew.

Inter-basin transfer: Water that either naturally (due to the alignment of the rock) or with human involvement (pumps and pipes) moves from one drainage basin to another.

Outputs: When water leaves a drainage system.

Evaporation: The process of water turning from a liquid into a vapour. Evaporation only takes place from a body of water e.g. a lake, puddle or the sea.

Transpiration: The evaporation of water from vegetation.

Evapotranspiration: The combined action of evaporation and transpiration

Inter-basin transfer: Water that either naturally (due to the alignment of the rock) or with human involvement (pumps and pipes) moves from one drainage basin to another.

River discharge via channel flow: Water entering the sea and leaving a drainage basin. A very small amount of water also enters the sea via throughflow and groundwater flow (baseflow).

Stores: When water is stationary and not moving in a drainage basin.

Interception: When water is caught and held by vegetation or man-made structures like buildings.

Surface store: When water is held in the surface of the earth. This may be a puddle, a lake or a garden pond.

Soil moisture store: When water is held in unsaturated soil.

Groundwater store: When water is held in saturated ground.

Transfers (flows): When water is moving within a drainage basin.

Stem flow: When intercepted water runs down the trunks and stems of vegetation.

Canopy drip: When intercepted water drips off the leaves of vegetation (drip tip leaves in rainforests are actually designed to allow this to happen).

Throughfall: Precipitation that falls directly through vegetation.

Infiltration: Water that moves from the surface of the earth into the soil below.

Throughflow: Water that travels through unsaturated ground.

Pipeflow: Water that travels through holes left by root systems and animals burrows.

Percolation: Water that travels from unsaturated into saturated ground.

Groundwater flow (baseflow): Water that travels through saturated ground.

Capillary action (or rise): Water that may move upwards towards the surface.

Channel flow: Water that travels in a river.

Surface run-off (overland flow): When water travels across the surface of the earth e.g. down a hill.

2.2 Discharge – the volume of water passing a given point over a given time.

Discharge is found by multiplying the cross-sectional area of a river (stream) by the mean velocity of the water. Steeper slopes should lead to higher velocities because of the influence of gravity. Velocity also increases as a stream moves from pools of low gradient to rapids. Discharge is normally expressed in cubic metres per second (cumecs). Discharge usually increases downstream as does width, depth and velocity. By contrast channel roughness decreases. The increase downstream in channel width is normally greater than that of channel depth. large rivers with a higher width/depth ratio are more efficient than smaller rivers with a lower w/d ratio, since less energy is being spent in overcoming friction. thus the carrying capacity increases and a lower gradient is required to transport the load. Although river gradients decrease downstream, the load carried is spaller and therefore easier to transport.

Velocity – The velocity of a river is the speed at which water flows along it. The velocity will change along the course of any river, and is determined by factors such as the gradient ( how steeply the river is losing height), the volume of water, the shape of the river channel and the amount of friction created by the bed, rocks and plants.

Channel shape – The efficiency of a rivers channel is measured by finding its Hydraulic radius. It is the ratio between the length of wetted perimeter and cross section of a river channel.

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Wetted perimeter: the entire length of the riverbed bank and sides in contact with water.

The Bradshaw model of channel variables.

Channel roughness – It is often thought that the velocity of a river is greatest near its start. This is not the case, as large angular boulders create a rough channel shape and therefore, a large amount of its bed friction. This creates more resistance to flow than a river with smooth clays and silt forming its banks. The roughness coefficient is measured using Manning’s ‘n’, which shows the relationship between channel roughness and velocity.

Regimes- variations in a river flow

The regime of a river is expected to have a seasonal pattern of discharge during the year. This is due to factors such as climate, local geology and human interaction. Equatorial rivers have regular regimes but in the UK where seasons exist one or two peaks may be recognisable.

Simple regimes – these show times of high water levels followed by lower levels. They exist as a result of a glacier melt, Snowmelt, or seasonal rainfalls such as monsoons.

Complex regimes – if a river has more than one period of high water levels and/or low water levels, a more complex regime results. It is more common on large rivers that flow through a variety of relief and receive their water supply from large tributaries, for example, The Rhine.

Rivers flow

There are two types of flow: Laminar Flow: This rarely occurs, water flows smoothly in a straight channel. It is most common in the lower parts of a river.

Turbulent flow: This is far more common, it occurs where the shape of the rivers channel is varied with pools, meanders, and rapids. A great deal of turbulence results in sediment being disturbed. The greater the velocity the larger the quantity and size of particles that can be transported.
2.3 Hydrographs

Rivers Storm_Hydrograph

A storm hydrograph is a way of displaying how the discharge of a river can change over time in response to a rainfall event.  The discharge of a river is just the amount of water passing a certain point every second, and is calculated by multiplying the cross sectional area of the river by the velocity.

Storm hydrographs – by Sofia

Influences on the hydrographs and drainage basin

Drainage basins all have a variety of characteristics in terms of vegetation, geology, soil type and so on, all of which interact to influence how quickly or slowly river discharge increases after a storm.

Factors affecting a river’s discharge:

Rock and soil type
·        Permeable rocks ad soils (such as sandy soils) absorb water easily, so surface run-off is rare
·        Impermeable rock and soils (such as clay soils) are more closely packed. Rainwater can’t infiltrate, so water reaches the river more quickly
·        Pervious rocks (like limestone) allow water to pass through joints, and porous rocks (like chalk) have spaces between the rock particles
Land use
·        In urban areas, surfaces like roads are impermeable – water can’t soak into the ground. Instead, it runs into drains, gathers speed and joins rainwater from
other drains – eventually spilling into the river
·        In rural areas, ploughing up and down (instead of across) hillsides creates channels which allow rainwater to reach rivers faster increasing discharge
·        Deforestation means less interception, so rain reaches the ground faster. The ground is likely to become saturated and surface run-off will increase
Rainfall
·       The amount and type of rainfall will affect a river’s discharge
·       Antecedent rainfall is rain that has already happened. It can mean that the ground has become saturated. Further rain will then flow as surface run-off towards the river
·        Heavy continual rain, or melting snow, means more water flowing into the river
Relief
·       Steep slopes mean that rainwater is likely to run straight over the surface before it can infiltrate. On more gentle slopes infiltration is more likely.
Weather conditions
·       Hot dry weather can bake the soil, so that when it rains the water can’t soak in. Instead, it will run off the surface, straight into the river.
·      High temperatures increase evaporation rates from water surfaces, and transpiration from plants – reducing discharge
·       Long periods of extreme cold weather can lead to frozen ground, so that water can’t soak in

2.4 Floods

Bangladesh - floods

Bangladesh – floods

 

Map highlighting the reasons for these floods.

Map highlighting the reasons for these floods.

Bangladesh Floods

Bangladesh Floods

Tewkesbury floods – 2007

Tewkesbury is situated in Gloucestershire, see Figure 10, and was the worst affected part of the county when the floods hit in July 2007. It was widely reported in the media, particularly images of the Abbey which became surrounded by flood water.

Tewkesbury mapgb_3_388000_231000_1986Physical Causes 

Tewkesbury is vulnerable to flood events due to its geographical location with two sizeable rivers, the Severn and the Avon, meeting in the town which both overflowed their banks .

tewkesbury photo flood news-graphics-2007-_641437a
The summer of 2007 in England and Wales was the wettest since records began in 1766 due to a low pressure system over the UK, with an extreme event on July 20th

Little sunshine meant evaporation rates were low, which when combined with intense rainfall led to extreme flooding.

  • The jet stream was located further south than usual since early June of 2007, with a train of waves from the North Pacific to Europe and a trough occurring near to the UK. This led to Atlantic weather systems being ‘steered towards the UK’ which were slow moving meaning prolonged rainfall events. In addition the trough near the UK caused air to move from a more southerly track than is expected, leading to air carrying more moisture due to it passing over warm seas .
  • The flooding of southern and central England on July 20th was a result of a low pressure system located over Calais in the morning which slowly moved Northwest bringing warm, continental air. This, when meeting the cooler air to the North, created an area of instability ideal for storm generation.
  • Soils were already saturated due to the heavy rainfall occurring in the months leading up to the flooding. This meant water could not infiltrate into the ground, causing overland flow and intensifying the floods.
  • Social Effects
· 13 people lost their lives and hundreds had to be evacuated
· Significant damage to most properties in the area (Figure 13) with nearly 50,000 homes affected, with people losing treasured, personal belongings and made homeless- staying with friends or relatives and 850 families had to stay in caravans, some up to Christmas 2008.
· Infrastructure severely affected, with roads cut off and badly damaged.· On 22nd May water treatment works shut down. The media reporting’s of imminent loss of supplies, meant usage doubled and led to water depletion. By 24th July, 140,000 properties in Gloucestershire had no water supply. Alternative water supplies by bottles, bowsers and tankers had to be used, see Figure 14. Water supplies were not fully restored until the 1st August (Severn Trent Water, 2007)· 50,000 properties without power for 48 hours (Stuart-Menteth, 2007)
 Human Causes

· Building on floodplains

· No flood defences in Tewkesbury (Environment Agency, 2010).

Economic Impacts 
· Flooding cost local councils £140 million
· Total cost to UK economy estimated to be £3.2 billion
· 9,000 businesses affected (Figure 15)
· More than 180,000 insurance claims
Agriculture sector severely affected and where floodwater contained sewage crops had to be destroyed. 

 

3. Management issues and strategies

3.1 Dams and reservoirs

Three Gorges Dam - China

Three Gorges Dam – China

 Hydrological changes resulting from the construction of dams and reservoirs:

Changes to the hydrology upstream of dams 

Increased evaporation rates because reservoirs have a larger surface area than rivers.

An increase in the amount of surface store (reservoirs are an artificial store).

A reduction in the velocity of the river upstream. The river was effectively flowing into a stationary store of water.

Increased sedimentation can lower the depth of the river and the reservoir. Again this will reduce velocity and may also reduce storage capacity.

Changes to the hydrology downstream of dams –

River discharge will decrease because water is being held behind the dam.

A rivers’ discharge may become more regular (less extremes) because the flow of water is regulated.

Clear water erosion may cause the bed of the river to lower. There is no sediment (load) to be deposited to replace erosion.

The amount of load transported by the river will reduce because less sediment is reaching downstream.

The salinity of the water and the ground may increase.

The temperature of the water may reduce, as water released from reservoirs is often colder (reservoir deeper than river).

The water may also be less oxygenated than natural free flowing water.

With smaller discharge the velocity of the river may decrease, because the level of the river is further below bank-full discharge so the hydraulic radius is smaller.

The amount of depositional landforms may reduce e.g. alluvial fans, levees, deltas and slip off slopes.

To examine the costs and benefits of dams and reservoirs as part of multi-purpose schemes.

  1. Locate the Three Gorges Dam – with a map and a written description.
  2. How is the Three Gorges Dam a ‘multi-purpose scheme’?
  3. Make detailed notes on the benefits of the Three Gorges Dam Project – using the SEEP (Social, Economic, Environmental and Political).
  4. Make detailed notes on the costs of the Three Gorges Dam Project – using the SEEP (Social, Economic, Environmental and Political).
Three Gorges Dam

Three Gorges Dam

Fresh water Threegorges

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3.2 Floodplain management (there are three sections in this unit)

1. Channel processes and fluvial landforms

Erosion

Erosion is the wearing away of something. When talking about rivers it normally means the wearing away of the bed, banks and its load. Types of erosion are:
Attrition: This when load in a rivers flow crash into each other, causing pieces to break off.
Hydraulic Action: This is when air and water gets trapped in cracks on a rivers beds and banks. The build up of pressure within the cracks causes bits of the bed and banks to break off and the cracks to get bigger.
Corrosion (solution): When the slight acidity of water cause bits of load and the bed and the banks to dissolve.
Corrasion (abrasion): When bits of load crash into the bed and banks. This process causes the load, bed and banks to wear away.

Transportation

When a river has surplus energy it may carry some of the material that it has eroded. The different types of erosion are:
Traction: Load that is rolled along the bed of the river.
Saltation: Load that is bounced along the bed of the river.
Suspension: Load that is transported in a rivers’ flow (current).
Solution: Load that is dissolved by a river and then transported by it.
Flotation: Material transported on the surface of a river.

River transportation

River transportation

The larger pieces of material tend to be transported along a rivers’ bed. As they get smaller they can they be transported in the current (flow). Only the smallest bits may be dissolved.
The processes of erosion and transportation tend to make a rivers’ load smoother and rounder as you move from the source to the mouth.

Deposition

When the velocity of a river falls causing its energy to fall. Because the energy of the river is falling so does its capacity and competence, causing to put down its load. This process of putting down load is deposition.

Hjulstrom Curve: A graph that shows the relationship between river velocity and particle size when looking at a rivers’ ability to erode. transport and deposit.

The Hjulström Curve is a graph used to determine whether a river will erode, transport, or deposit sediment depending upon the flow velocity. The x-axis shows the size of the particles in mm. The y-axis shows the velocity of the river in cm/s.

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Competence: The maximum diameter of a piece of load that a river can transport.
Capacity: The maximum amount of load that a river can transport.
Critical Erosion Velocity: The minimum velocity that a river needs to be traveling for it to start eroding and then transporting material.
Settling (or fall) Velocity: The velocity that a river needs to fall below to start depositing its load.

What apparent anomaly with the Hjulstrom curve is that it can erode sand at a much lower velocity than it can erode clay and silt. This is because that clay and silt are very cohesive (they stick together). This means that even though the particles sizes are small they have a very strong bond between them.

 

A rivers course is often divided into the upper course, the middle course and the lower course.

River course

River course

Upper Course: This is the section of the river nearest the source. This is where load is biggest and most erosion is vertical. Most landforms are made by erosion and include; waterfalls, gorges, rapids, v-shaped valleys and interlocking spurs.
Middle Course: This is the section when the river leaves the mountains and enters are more hilly environment. The valley floors starts to widen as you get more horizontal erosion. The landforms that you get in the middle course include alluvial fans and meanders.
Lower Course: This is the section closest to the mouth. Here the river is travelling over much flatter land and the load is much smaller and smoother. This is more horizontal erosion here as the river nears its base level. The landforms you find in the lower course include meanders, oxbow lakes, braided rivers, levees and deltas.
Classification of Landforms: As well as classifying landforms as upper, middle and lower course landforms, it is also possible to classify them as erosional, depositional and erosional and depositional.
Alluvial River: An alluvial river is any river that carries load. Nearly all rivers (except some rivers flowing over ice shelves and glaciers) carry load.
Fluvial: Anything found on or made by a river. This includes all landforms.

Define the following terms:

Meanders, Slip-off Slope (point bar), River Cliff, Thalweg, Sinuous.

Meander

Meander

Levees: Levees are embankments found on the sides of a river channel. Levees can be made by or enlarged by humans, but we are only interested in levees that are made naturally. Levees are made when a river exceeds bankfull discharge i.e. it is in flood.

Describe the formation of a levee.

Levee formation

Levee formation

Oxbow Lake: An oxbow lake is a meander that has become cut off from the main river channel. If you have the outside of two meanders near each other they will eventually connect. They connect because erosion is at its maximum on the outside of the meander. When they eventually connect the thalweg (fastest flow) will no longer go around the old meander, but actually go in a straight line. This meas that the outside of the river channel now has a slower flow so deposition takes place cutting off the old meander.

Ox-bow lake

Ox-bow lake

Braided River: A braided river is a river with a number of smaller channels, separated by small and often temporary islands called eyots. Braided rivers usually form on rivers with variable flow (wet and dry season or snow melt season) and high quantities of load. When a river is at maximum discharge it is able to transport most of its load. However, when the discharge falls along with the velocity an energy of the river, deposition starts to take place, creating eyots.

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Floodplain

Floodplain

Floodplain: The floor of the valley floor that gets flooded when a river exceeds bankfull discharge. Floodplains tend to be much wider in a rivers’ lower course where horizontal erosion has had a greater effect.
Bluff line: The outer limits of the floodplain. The bluff line is basically the edge of the valley floor.
Strand line: A line of load (usually sticks and litter) that is deposited at the limit of a flood.
Alluvial deposits (alluvium): Load that is deposited by a river in time of flood.

Floodplain

Floodplain

 

2. Human modification of a floodplain

The construction of a multi-purpose dam scheme is a human modification to a floodplain. therefore, the note you made on the section above (Three Gorges Dam – China) should help with the answering of this question. However, it does need to be tailored to the specific question.

The Colorado River – Case study

Colorado River - drought concerns.

Colorado River – drought concerns.

Ways in which humans have modified rivers:

  • Urbanisation: Urbanisation tends to cause deforestation reducing interception and transpiration. Sewers also reduce surface stores and therefore evaporation. Urban areas usually create large impermeable surfaces which can lead to greater surface run-off.
  • Sewer Systems: Generally sewer systems create artificial channels, which often reduces a rivers’ lag time and can lead to increased flooding downstream.
  • Pollution: Transport, industry and housing all create pollution which works its way into the water system. Areas that don’t have proper sewers and water treatment tend to be effected more. Metals and chemicals are particularly polluting.
  • Water table (groundwater depletion): Unsustainable use of groundwater can cause subsidence. Mexico City has experienced subsidence because of aquifer depletion underneath the city. On the scale, London has actually seen its water table rise since deindustrialisation has meant the demand for water has fallen.
  • Deforestation: Deforestation reduces interception and transpiration. Removal of trees can also increase the risk of mudslide by reducing slope stability and stops root uptake. Less interception speeds up the rate the ground become saturated and therefore increases the risk of flooding
  • Micro-climate: Urban areas create heat islands which can increase convectional rainfall. Particulates released by industry and transport also make excellent condensation nuclei.
  • Channelisation: Artificially smoothing channels may remove river discharge from one area, but areas down stream that haven’t been smoothed are likely to experience an increase risk of flooding.

3. Alternative stream management strategies (costs and benefits)

 

The Mississippi River rushes through a break last June in the Indian Grave Drainage District levee north of Quincy, Ill., and south of the town of Meyer, Ill., causing major flooding.

The Mississippi River rushes through a break last June in the Indian Grave Drainage District levee north of Quincy, Ill., and south of the town of Meyer, Ill., causing major flooding.

Channel Enlargement (widening/deepening), Channel Straightening, Flood Relief Channels, Artificial Stores, Flood Embankments (levees), Controlled Flooding, Afforestation / Reforestation, Flood Proofing, Land Use Planning (zoning), Contour Ploughing and Strip Cultivation, Interception Channels, Settlement Removal, Dams, Channelisation, Dredging, River bank conservation, River restoration.

Definition and each one works. Then say what are the advantages and disadvantages.

Mississippi - Levees

Mississippi – Levees

Mississippi River and Tributaries’ (MR&T) levees currently protect more than 4 million citizens, 1.5 million homes, 33,000 farms, and countless vital transportation routes from destructive floods. The levees are designed to protect the alluvial valley against the project flood by confining flow to the leveed channel, except where it enters the natural backwater areas or is diverted purposely into the floodway areas.

3.3 Groundwater management

Groundwater – water which is contained within the pore and crevices of soils and rocks.

freshwater aquifergrndwtr

CAUSES OF GROUNDWATER USAGE

  • Evapotranspiration from shallow stores, capillary action will draw moisture up to near the surface
  • Natural discharge by springs and into lakes, rivers and oceans
  • Artificial abstraction (removal) for domestic, industrial and agricultural use
  • Leakage into nearby aquifers
  • Interbasin transfers

CAUSES OF GROUNDWATER RECHARGE

  • Artificial recharge. Either leakage from irrigation channels and reservoirs or the pumping of water into aquifers.
  • Infiltration and percolation after precipitation or snow melt
  • Seepage from river channels, lakes and oceans
  • Leakage from nearby aquifers
  • Interbasin transfers

Click on the link (below) word document (worksheet) for ground water

Groundwater

 

3.4 Freshwater wetland management

Kissimmee River - Florida U.S.A

Kissimmee River – Florida U.S.A

A wetland is an area of land where soil is saturated with moisture either permanently or seasonally. Such areas may also be covered partially or completely by shallow pools of water. Wetlands include swamps, marshes and bogs. The water found in wetlands can be saltwater, freshwater, or brackish (a mixture of fresh and salt water). The world’s largest wetland is the Pantanal which straddles Brazil, Bolivia and Paraguay in South America.
Brackish water: Water that has a higher salinity content than freshwater, but not as high as saltwater.

Ramsar Convention: The Ramsar Convention is an international treaty for the conservation and sustainable utilisation of wetlands, i.e. to stem the progressive encroachment on and loss of wetlands now and in the future, recognising the fundamental ecological functions of wetlands and their economic, cultural, scientific, and recreational value. It is named after the town of Ramsar in Iran.  The convention was developed and adopted by participating nations at a meeting in Ramsar on February 2, 1971, and came into force on December 21, 1975.
The Ramsar List of Wetlands of International Importance now includes 1,888 sites (known as Ramsar Sites) covering around 1,853,000 km², up from 1,021 sites in 2000.

Importance of Wetlands

  • Flood control: Many wetlands are covered in vegetation which can intercept precipitation, absorb rainwater and transpire water. Wetland vegetation can also reduce the velocity of rivers flowing into them or from them and act as natural stores of water. If you remove or drain areas of wetland more pressure is placed upon the main river channel. Coastal and marine wetland areas can also absorb the energy of tropical storms, tsunamis etc.
  • Groundwater recharge: Wetlands can collect large areas of precipitation and river discharge. As this water is held in storage it will infiltrate and percolate into the ground to recharge groundwater.
  • Transport Network: Wetland provide many natural waterways that people can move around on easily.
  • Tourism and Leisure: Some wetlands, like the everglades in Florida or the fens in East England become tourist attractions. They also become popular locations to bird watch, fish and hunt.
  • Flora and Fauna: Many wetlands are unique habitats that support indigenous aquatic plants and animals. Many wetlands support rare reptilian and amphibian species. Many migratory birds also rest in wetlands flying to and from nesting and breeding grounds.
  • Fisheries: Wetlands can support large numbers of fish which can support local populations. Wetlands are not normally viable commercial fisheries.
  • Water purification: The soils, geology and vegetation of wetlands can help clean and purify water.
  • Storage of organic matter: Wetlands support large areas of organic matter that can hold large stores of methane (greenhouse gas).
  • Coastal stabalisation: Wetlands that occur along the coastline and on river banks have prevent erosion from the sea or by rivers.

Factors Causing Loss and Degradation of Wetlands

  • Increased demand for agricultural land: As the world population grows there is an increasing demand for food. With the amount of viable agricultural land decreasing, increasingly areas of wetland are being artificially drained to make ways for agricultural land e.g. the draining of the fens in East England.
  • Population growth: As the world’s population grows, it demands more water, more food and more land. The increasing demand for water can mean wetlands are drained of their water or their source of water. This problems is made worse as the world’s population develops and uses more water e.g. showers and toilets.
  • Urbanisation: With the world population growing, there is a greater demand for housing. Increasingly this demand for housing is in urban areas. With urban areas growing more and more wetland areas are being drained or inhabited. Urbanisation on or near wetlands can cause pollution, changes in river flow and river channels and disturbance of wildlife. Land reclamation is the process of reclaiming land from the water.
  • Sea level rises: Global warming is causing glaciers and ice sheets to melt causing sea levels to rise. These rising sea levels can flood coastal and marine wetland areas. Even if the whole wetland is not flooded, water conditions can be changed from fresh to brackish.
  • River flow changes: Many rivers have been channelised and straightened, reducing the amount of wetlands. Others have been drained or dams have altered flow. Some have been polluted or redirected. All these natural changes are removing or changing the ecosystems of many wetland areas.
  • Pollution: Any form of pollution, but particular chemicals and metals can change the delicate ecosystems of wetlands. Process like eutrophication, caused by fertiliser run-off can completely kill whole wetland areas by preventing the wetland oxygenating properly and receiving sunlight.
  • Infrastructure projects: As populations grow and we become more mobile, there is an increasing demand for new roads, airports, railways. etc. Unfortunately wetlands are often drained or disrupted (bridges, dykes and causeways) to make way for these projects.
  • Alien species invasion: Many alien species like the cane toad in Australia or the American mink in the UK have been introduced to wetlands and devastated indigenous species. The introduction of any alien, however small can disrupt food webs and ecosystems.
  • Tropical storms: Although wetlands can be a natural defence against tsunamis and tropical storms, they can also been damaged by them. Freshwater wetlands in particular can be flooded by storms surges associated with tropical storms, changing the salinity of water and damaging vegetation.

 

Kissimmee River

Kissimmee

Kissimmee

Kissimmee Restoration

Problems associated with the restoration

Click on the link (below) worksheet dealing with the issues surrounding wetlands:

Freshwater Wetland Management-worddoc

Freshwater wetland – case study management

3.4 Irrigation and agriculture

Agriculture: Agriculture the artificial cultivation (growing or rearing) of plants or animals. Agriculture that grows crops is known as arable agriculture, agriculture that involves rearing animals is known as pastoral agriculture.

Irrigation: This means artificially watering the land. There are three main types of irrigation; gravity flow, sprinklers and drip systems.

Eutrophication: This is the processing of artificially adding nitrates and phosphates (through fertilsers and sewage) to wetland areas e.g. rivers and lakes. The added nitrates and phosphates causing excessive growth of algaes. The algae growth can reduce the oxygen content of the water as well as reducing the amount of sunlight that it receives. The nitrates and phosphates often come from agro-chemical run-off, but can also come from domestic sewage and industrial waste.

Salinisation: This is the increase in the salt content of water. Salinisation can happen because of evaporation or unsustainable water extraction. If the water become to salinated it becomes less fertile.

GROWING DEMAND FOR AGRICULTURAL PRODUCTS

  • The world’s population is growing. The current population is about 7 billion, but it is expected to peak at nearer to 9 billion.
  • Because fossil fuels are finite, alternative forms of energy are being looked at. One form of renewable energy being used are biofuels. Biofuels are made out of biological matter and therefore are increasing the demand for agricultural products.
  • Economic development. As more of the world’s population is removed from poverty, their calorific intake increases. This increase in food consumption, is increasing the demand for agricultural products.
  • Pastoral farming. As the world population increase, the demand for meat also increases. Most farm animals are omnivores or herbivores so need agricultural products like corn to eat.

DECREASING SUPPLY OF AGRICULTURAL PRODUCTS OR LAND

  • Urbanisation. As the world develops, urbanisation increases tends to happen increasing the size of urban areas. As urban areas grow they eat into greenfield sites in rural areas, reducing the amount of agricultural land.
  • Land degradation and desertification. Land that is overcultivated or overgrazed can become degraded (less fertile). AS farmers try to react to demand by growing more intensively, more land is being degraded. In extreme circumstances, the land may turn to desert (desertification).
  • Rising sea levels. Some of the earth’s most fertile agricultural areas are floodplains and deltas. As world sea levels (eustatic changes) increase much of this fertile land is lost.
  • Conversion to biofuels. Although not strictly reducing the amount of agricultural products (biofuels are agricultural products), this does decrease the supply of agricultural products available for human consumption. Biofuels are often favoured by farmers, because they demand a higher price.
  • Hazards. Natural hazards like tropical storms, volcanoes and tsunamis can reduce the amount of agricultural land available for cultivation.
  • Disease. There is an increasing amount of intensive monoculture (growing of one crop) taking place. Monoculture always runs the risk of been impacted by the outbreak of diseases or pests that attack the particular crop e.g. wheat leaf rust fungus.

 

 

4. Competing demand for water

4.1 Conflict at the local or national scale

IB Water Conflicts at the local or national scale Word document

water before-after-bridge630

http://www.motherjones.com/kevin-drum/2015/04/california-drought-photo-water-bridge

http://www.youtube.com/watch?v=hnpamY0m65I

http://www.theguardian.com/environment/gallery/2014/aug/20/drought-in-california-in-pictures

Guardian – global water shortage is a threat and can cause terror and war

 

 

 

7 Comments
  1. how can i find out who is the author of blog ?

  2. And when did you write this section? Could you kindly help me please? Thanks

  3. What would you like to know?

  4. 51188 permalink

    Where did you find the data for the Hjulström Curve example. Thanks

    • Good morning – I will have to do a little investigating as to where I obtained the image. How desperate are you for the location of this graph?

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