Option A Freshwater - Drainage Basins

Question 1

Define a drainage basin

Answer 1

Area where all accumulated water supplied by percipitation is transferred to a particular ocean, lake or larger stream.

Question 2

What is the hydrological cycle

Answer 2

The cycle of water between the biosphere, atmosphere, lithosphere and hydrosphere.

The cycle is seen in drainage basins and can be broken down into inputs, outputs, flows and stores.

Question 3

What are the inputs and outputs of a drainage basin?

Answer 3

Inputs:
Percipitation

Outputs:
Evaporation
Evapotranspiration

Question 4

What is evapotranspiration (P.EVT)?

Answer 4

The potential EVT if there was an unlimited supply of water

Question 5

What are the different flows in a drainage basin?

Answer 5

Infiltration: water soaks into the soil or rock beneath, infiltration capacity is the maximum rate.
Overland flow: flow of water over the land’s surface, occurs when soil is saturated or at infiltration capacity.
Through flow: water flowing through the soil in natural pipes and percolines.
Base flow: part of the river’s discharge provided by groundwater seeping into the bed of a river. Constant, though can increase in wet periods.

Question 6

What are the different stores in a drainage basin?

Answer 6

Vegetation - water caught and stored by plants
Soil - subsurface water in the soil
Aquifers - permeable rock that acts as an underground reservoir of water

Question 7

What are the three main components of water stored in vegetation?

Answer 7

Interception: water retained by the plant surface and later evaporated.

Throughfall: water falling through gaps in the vegetation dropping from leaves, twigs or stems.

Stemflow: water that trickles along twigs and branches and finally the main trunk.

Question 8

Describe the water store of soil.

Answer 8

Soil moisture is the subsurface water in the soil.

Field capacity is the water held in the soil after excess water drains away.

Wilting point defines the point at which plants can no longer take water from the soil.

Question 9

Explain the processes surrounding aquifers and why they’re important

Answer 9

As water moves from soil to bedrock in percolation, it reaches a permanently saturated zone within the rock, the water table.

The permeability of the rocks dictates how quickly the water gets there.

The water table varies seasonally through the aeration zone. 96.5% of freshwater is from the ground and takes a prolonged period to recycle, hence it is considered non-renewable in certain locations.

The recycling process is known as recharge and occurs by infiltration, seepage, groundwater leakage, and artificial recharge from irrigation.

Question 10

What is the cryosphere?

Answer 10

The snow and ice environment.

Up to 2/3 of the world’s freshwater is in the form of snow and ice.

Question 11

What does the Bradshaw model define?

Answer 11

The Bradshaw model approximates changes in the characteristics of a river downstream.

Increase:
Discharge
Occupied Channel Width
Water depth
Water velocity
Load quantity

Decrease:
Load particle size
Channel bed roughness
Slope angle

Question 12

Summarise water flow in rivers.

Answer 12

HAAS, SSST, laminar, trubulent, cavitation, velocities, meanders, oxbow lakes, waterfalls, rapids.

Question 13

How are floodplains, meanders, levees, waterfalls and deltas formed?

Answer 13

Waterfalls: Layer of HR over layer of SR. SR erodes faster, forms rapids, plunge pool, undercut, overhanging cliff collapses, retreats, gorge.

Flood plains: Areas of low relief formed by deposition when a river floods. Alluvium is deposited on the land in times of flooding increasing the height of the floodplain.

Meanders: small disruption in channels such as pool, riffle or bend cause imbalanced erosion. Imbalance grows causing a curve. The curve bends further until a thin neck is formed. After continuous flooding, neck breaks, and river straightenes, an oxbow lake is formed.

Levees: deposition of coarse material near the channel while finer deposits are further in the floodplain. Raised banks at the edge of the river. Heavier deposited first due to high energy requirements.

Deltas: When a stream flows into a standing body of water. Loss of energy and a large volume of sediment being deposited. Salty water speeds up process through flocculation.

Question 14

What is a storm hydrograph and what does each section represent

Answer 14

Show how a river’s discharge changes throughout a particular event.

Rising and recessional limb - rise and fall of discharge.
Peak discharge - highest point on the graph.
Lag time - time between peak rainfall and peak discharge.

Size - Affected by basin, rainfall, geology and surroundings.
Flows - Base flow, through flow, and overground flow.

Question 15

What influence does geology have on how a river reacts to storms?

Answer 15

Impermeable surfaces generate more overland flow - shorter lag time and higher peak flow.

Question 16

River regimes?

Influence of seasonality?

Answer 16

River regimes are the seasonal variation in the flow of a river.

Seasonal changes in climate generally have the greatest impact on river flow.

Question 17

Describe flood risk.

Answer 17

Most river floods are contained within a river’s floodplain.

Larger floods occur less often and cover larger parts of the plain. Increased intensity, decreased frequency.

Question 18

What factors impact flood risk?

Answer 18

Precipitation type and intensity

Temperature and evapotranspiration

Antecedent moisture

Drainage density

Porosity and impermeability

Slopes

Vegetation type

Land use

Question 19

What effect does urbanisation have on river flow? How is this seen on a storm hydrograph?

Answer 19

Impermeable surfaces in urbanised spaces cause more surface runoff with drainage channels. This leads to:

• Shorter lag times
• steeper rising limbs
• higher peak flows
• steeper recessional limb#

Magnitude and frequency of floods are increased in at least 3 ways

• Creation of impermeable surfaces
• Smooth surfaces and dense drainage network
• River channels constricted by riverside facilities, roads, bridges

It can have conflicting impacts on hydrological processes:

• More water leading to increased erosion
• Increased speed of flow and material due to enlarged channels
• Less erosion at riverbank protection schemes

Question 20

Effect of deforestation on river flow

Answer 20

Presence of vegetation increases interception, reduces overland flow and increases evapotranspiration.

Deforestation contrasts each aspect.

• More overland flow leading to more frequent erosion
• River transporting more sediment
• Reduced evapotranspiration

Risk of higher magnitude floods of greater frequency.

Question 21

Effect of channel modifications on river flow

Answer 21

Include channelisation, enlargement, and straightening. (C,E,S)

C and S form straight channels that speed up the water reducing lag time.

E enables more water flow increasing peak flow.

Purpose is to remove water from an area, works up to a point where severe floods could destroy modifications as in Mississippi and Hurricane Katrina.

Question 22

What are the 2 types of flood mitigation strategies with examples?

Answer 22

There are hard (dams, channel modification) and soft engineering schemes (planning, afforestation).

Question 23

+- of Dams

Answer 23

Dams can control a river’s water flow, mitigating flood risk during periods of high precipitation. The Aswan Dam along the Egyptian Nile benefits tourism, agriculture, and power (10 Billion KWh).

Dams can cause increased water loss due to evaporation, clear water erosion, and a decline in sediments reaching estuaries.

Reservoirs need land that is flooded in creation.

Question 24

What is flood abatement? What pros and cons are there with afforestation?

Answer 24

Flood abatement involves the decrease of run-off reducing flood peak in a drainage basin.

This can include:
- Afforestation
- Reseeding of sparley vegetated areas
- Treatment of slopes to reduce run-off coefficient with terracing
- Vegetation protection from fires, grazing and cutting
- Sediment or debris clearance in headwater streams
- Construction of small water and sediment-holding areas
- preservation of natural water storage
=====
Before the trees fully grow in afforestation, sediment loads can increase before the trees come into effect reducing overland flow and increasing interception.
-
Reduced runoff and soil erosion
Enhanced water absorption
Improved riverbank stability
Increased Carbon Sequestration
Ecosystem and biodiversity support
-
Time-intensive
High initial cost and maintenence
Tree water demand in scarce areas
Fast-growing non-natives may disrupt ecosystem

Question 25

What examples of channel modifications are there? What are the pros and cons?

Answer 25

Artificial levees are most common and can be used to divert water to low-value land on the flood plain.
-
Dredging of sediment will increase the carrying capacity of the river.
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Increased flow capacity
Direct flood control
Reduced erosion
Controlled water flow
Versatile design options
-
Environmnetal disruption
Increased downstream flooding
High costs
Reduced water quality, higher sediment levels and pollution downstream
Ongoing maintenance

Question 26

What does planning include as a mitigation strategy? What are the pros and cons of it?

Answer 26

Includes:
- Personal insurance
- Sand bags
- Sealing doors and windows
- Moving valuables upstairs
- Electrical generators upstairs
- Home design with electrics above expected flood level
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Cost-effective
Quick Implementation
Reduces personal loss
Safety enhancement
Minimizes damage
Adaptable everywhere
-
Limited effectiveness in severe cases
Personal burden who may lack resources
Insurance gaps in high risk areas
Maintenance and upkeep
Not a measure of prevention

Question 27

What is risk sharing? Examples.

Answer 27

Risk sharing is a form of ​community preparedness​, whereby the community ​shares the risk ​posed by a natural hazard and ​invests collectively to mitigate the impacts of ​future hazards​.

Government disaster relief funds or disaster aid can be money, equipment, stand and technical assistance given to a community following a disaster.

Flood insurance programs are important, many flood-prone households aren’t insured or are underinsured. Residence in LICs and new-builds on floodplains in the UK are unable to obtain flood insurance.

Question 28

What things could be done to improve flood warnings?

Answer 28

Improved rainfall and snow-pack estimates.

Better gauging of rivers, meteorological information, channel mapping.

Better more current information about populations, infrastructure, elevation and stream channels incorporated in risk assessments.

Sharing of information between forecasters, national agencies, relief organisations and the general public.

More complete and timely sharing of meteorological and hydrological information among countries of international drainage basins.

Global share of technology among all agencies involved in flood forecasting and risk assessment.

Question 29

Why might forecasting be, or become less helpful?

Answer 29

Increased uncertainty due to global climate change.

Floods are predicted to become more intense and frequent.

More erratic rainfall patterns.

50% of unprotected dwellings in England have less than 6 hours of flood warning time.

However, people do have more access to ICT allowing for a population that is more up-to-date with weather warnings.

Question 30

What is water scarcity?

Answer 30

Physical water scarcity: where water consumption exceeds 60% of the usable supply.

Economic water scarcity: where a country has sufficient water to meet its needs, but requires more infrastructure such as storage or transport.

Question 31

How much of the world’s water is fresh?

Where is most of our water used?

Answer 31

97.5% of water is oceans. 2.5% is fresh where 0.4% of it is on the surface and in the atmosphere.

Agriculture 93%
Industrial and domestic use 7%

Question 32

What is a drought? What effects does it have?

Answer 32

Extended period of dry weather leading to conditions of extreme dryness.

Absolute drought <0.2mm for at least 15 days. Extreme shortage.
Partial drought <0.2mm for at least 29 days. Less severe with occasional rainfall.

Some droughts are seasonal. Some linked to El Nino events.

Severity depends on length and water shortage severity.

Reduced crop yields
animal mortality
illnesses linked to dehydration
forest fires
Domestic water use bans

Question 33

What affects water quantity?

Water quality?

Answer 33

Rates of rainfall
Evaporation
Use of water by plants
River and groundwater flows
——
Many people in developing countries lack access to safe and affordable water supplies and sanitation.

4 million deaths each year caused by water-related disease.

Quality is affected by:
- Organic waste in sewage
- fertilizers and pesticides
- Heavy metals and acids

Question 34

What is water stress?

Answer 34

When per capita, water supply is less than 1,700 cubic meters per year.

An area is in “water stress” when subject to frequent water shortages.

In 2016, 2.3 billion people lived in water-stressed areas.

Question 35

What is the trend of water use?

Answer 35

Increasing. Population has tripled between 1922 and 2016, but water use increased six-fold.

Question 36

Describe the process of eutrophication. (Pollution)

Answer 36

1. Excess nutrients enter a body of water by rainwater runoff (usually nitrates and phosphates from fertilizers).
2. Nutrients promote plant growth, especially algae.
3. Algae blooms form a layer on the water’s surface blocking sunlight.
4. Without sunlight, plants die.
5. Algae is decomposed by bacteria which increases biological oxygen demand.
6. Anoxia, oxygen starvation in water and aquatic life dies.

Question 37

Why is eutrophication a problem?

Stakeholders?

Answer 37

Undesirable effects in aquatic ecosystems.
Loss of fertiliser is an economic loss to farmers.
Affect to drinking water and human health. (Blue baby syndrome)
—–
Farmers who apply the fertilizer have increased yields.

Chemical companies that profit from the sale of fertilizers.

Government that may be achieving food security.

Customers with more reliable food supply and lower prices.

Water companies that provide water for consumers.

Question 38

How can eutrophicatoion be dealt with?

Answer 38

Using alternative types of fertilizer and detergent.
Regulating and reducing pollutants at the point of emission. E.g. at sewage treatment plants.
Restoring water quality by pumping mud from eutrophic lakes.

Question 39

What measures can be taken to reduce nitrate loss?

Answer 39

Avoiding using nitrogen fertilizer in wetter seasons.
Avoiding using nitrogen in fields next to bodies of fresh water.
Using less fertilizer after a dry year, less would have been washed away.
Barley straw prevents the growth of green algae by using nitrogen in decay.

Question 40

Describe the process of salinization. (Irrigation)

Answer 40

Soil salinization occurs through the accumulation of salts from irrigated water or fertilizers. Irrigated water contains dissolved salts, and as this water evaporates out of the soil, the salt remains left in the topsoil.

In arid regions, soil drainage is often poor, evaporation rates are high and the water table is low.

Unless salts are washed down below root level, soil salinity will stunt growth and eventually kill off all but the most resistant plants.

Poor drainage and evaporation concentrate salts on irrigated land. Even good-quality irrigation water contains some dissolved salt and can leave behind tonnes of salt per hectare each year.

Irrigation can raise groundwater levels to within a metre of the surface, bringing up more dissolved salts from the aquifer, subsoil and root zone.

Question 41

How can salinization be mitigated?

Answer 41

Using efficient irrigation techniques such as drip irrigation.
Alternating fresh and saline water for irrigation.
Leaching with fresh water to remove salts.

Often costly and unproductive.

Question 42

What stakeholders in involved in the mitigation of salinization?

Answer 42

Farmers - cultivate crops and decide on how they are irrigated, profit of how much they sell.
Consumers - receive food from the crops cultivated by the farmers.
The government - may be achieving food security but have to in place policies to maintain a salt-free land.

Question 43

What are the growing human pressures on lakes and aquifers?

Question 44

Case study of the River Nile

Answer 44

The completion of the Grand Ethiopian Renaissance Dam (GERD) in 2022, Africa’s largest hydroelectric project, has heightened tensions between Ethiopia, Egypt, and Sudan over the Nile’s water resources. The Nile provides approximately 97% of Egypt’s freshwater, essential for its 105 million citizens. Egypt depends heavily on the river to support agriculture, drinking water, and industry. Under a 1959 treaty with Sudan, Egypt claims rights to 66% of the Nile’s flow—a treaty that excluded Ethiopia, which contributes nearly 85% of the river’s total flow through the Blue Nile. Ethiopia sees the GERD as crucial to its development, aiming to produce over 5,000 megawatts of electricity, which would significantly enhance the country’s energy security and boost its economy.

Egypt fears that the GERD will restrict the river’s flow, reducing its already scarce water supply and threatening agriculture. Egypt’s leaders have insisted on a binding agreement with Ethiopia regarding the dam’s operation and filling schedule to ensure downstream protection. In recent years, as Ethiopia has filled the dam’s reservoir in stages, Egypt has expressed concern over the potential for reduced Nile flow during droughts or extended dry periods. The United Nations has warned that without a formalized agreement, the dispute could escalate into regional conflict.

Sudan, initially siding with Egypt, has taken a more nuanced stance, recognizing the potential benefits the GERD could offer, such as regulated water flow and reduced flooding along the Blue Nile. However, Sudan remains cautious, as mismanagement or rapid reservoir filling could pose risks to its population and agriculture.

With most upstream countries supporting Ethiopia’s right to develop its resources and dismissing Egypt’s historical veto rights, negotiations remain stalled. The GERD dispute underscores the urgent need for an enforceable, cooperative framework to manage the Nile’s waters sustainably, securing the livelihoods and stability of millions across East Africa.

Question 45

Grand Ethiopian Renaissance Dam Case Study

Answer 45

Context
- Ethiopia building Africa’s largest dam
- 1.8km wide and produce over 5000 megawatts of electricity
- More than double Ethiopia’s current output leaves ¾ of the population in the dark
- Cost over $5 billion
—–
Uncertainties of the dam
- Egypt fears it will be used for
irrigation reducing their supply
- If filled too quickly - reduces supply and Aswan Dam power output
- Sudan promised foreign investors an abundance of water for irrigation
—–
Benefits
- Sudan receives some of the power
- Prevent flooding in Sudan with stabilised flow
- Allows Sudan to consume more water for irrigation

Question 46

What is integrated drainage basin management?

Answer 46

It is increasingly recognized that floodplain embankments, while usually effective at reducing flood risk, may result in a variety of adverse consequences to the functioning of the river and its associated drainage basin.

IDBM is the process of coordinating the management, development, and conservation of water, land, and related resources within a river basin. The goal of IDBM is to balance the needs of environmental conservation with socio-economic development, while also preserving and restoring freshwater ecosystems.

Question 47

IDBM at the Mississippi Case Study

Answer 47

Context
- $50B dollars of agriculture annually and 92% of USAs farm exports
- 1/2 of US goods are produced with this water
—–
Threats
- Rising demand for water (Inc. in pop and consum.)
- Floods threaten people and economies
- Global demand for local products places pressures
- Most of infrastructure is ageing and needs replacing
—–
AGWI (America’s great watershed initiative)
- Aim to increase water availability, improve quality, and safeguard use for future
- Involves all stakeholders to help find solutions to challenges of managing the Mississippi’s basin
Measures: ecosystems, flood & risk control, supply, transportation, economy, and recreation

Goal 1: to support and enhance healthy and productive ecosystems — Mississippi struggles with poor water quality in many areas

Goal 2: To reduce flooding and flood risk by imposing flood control measures, helped with 2011 floods

Goal 3: enrich QoL for people and recreation-based economies by enhancing wetland areas of the river

Question 48

What is a wetland? and why are wetlands important?

Answer 48

Despite their ecological importance, wetlands have faced destruction for agriculture and development throughout the 20th century.
-
They play crucial roles in water storage, groundwater recharge, storm protection, and pollution reduction.
-
The Ramsar Convention classifies wetlands into natural and human-made types, highlighting their biodiversity and economic value, including clean water, fisheries, and recreational opportunities.
-
Wetlands are also vital for regulating water quantity and quality, as they can filter toxins and nutrients. However, climate change poses significant threats to these ecosystems, impacting their water levels and functions.
-
Adaptation to changing conditions will be crucial for wetland health, with ongoing uncertainties about extreme weather events, such as droughts and floods, affecting their resilience.
-
Overall, sustainable management is essential for preserving wetland ecosystems and their benefits.

Question 49

What is the Ramsar convention?

Answer 49

An international treaty to conserve wetlands,
defines wetlands as “areas of marsh, fen, peatland or water, whether
natural or artificial, permanent or temporary, with water that is static
or flowing, fresh, brackish or salt.”
=====
Aims to:
=====
- Designate wetlands of international importance in Ramsar sites list.
- Maintain ecological character of listed sites.
- Organise planning to achieve wise use of the wetlands.
- Designate wetlands as nature reserves

Question 50

Kissimmee River Case Study for possibilities of wetland areas in the future

Answer 50

Context

• Located in central Florida, river basin was diverse in wildlife
• Stretched for over 100 miles across a 1-2 mile floodplain
• Heavy seasonal rainfall inundated floodplain for long periods
• # Often year roundFlood control
  =====
• Extremely flat landscape, frequent heavy rain and limited drainage caused persistent floods
• 1954, permission was given to provide major flood protection
• River was deepened, widened, and straightened (dredged)
• # River could be managed with pools and impoundmentsEnvironmental damage
  =====
• Loss of river floodplain habitat, huge loss of fish and wildlife
• Bald eagle population declined 74%
• Lack of flower in old parts of river accumulated vegetation that dissolved oxygen levels in water (deadly level)
• # Wetlands turned to dry pasturesRestoration
  =====
• Environmental damage visible even before completion
• 1992, start of ecological integrity restoration of Kissimmee
• Fill up 22 miles of canal
• Remove control structures
• Reconstruct 10 miles of old river channel
• # 12,000 acres of wetland should be restoredEffects
  =====
• Mass reduction in organic deposits
• Wetland plants such as arrowhead thriving in floodplain
• Dissolved oxygen returned to normal levels
• # Many birds, ducks and invertebrates returned to habitatFuture plans
  =====
• More than 320 fished and wildlife species to benefit from this
• Essential for greater Everglades restoration project
• Used to educate scientists and engineers going forwards
• Generally will allow for more natural flow patterns
• Could bring more tourism to the area

Question 51

How does zoning support water management?

Answer 51

The EU’s 1991 Nitrates Directive aims to control pollution by designating nitrate vulnerable zones and advising against nitrogen fertilizer use, leading to improved water quality at monitored sites.

Question 52

How does water saving support water management?

Answer 52

Water can be conserved through various methods, such as using smaller baths, taking showers, and installing water-efficient fixtures. Turning off taps when not in use and fixing leaks are crucial. Dishwashers and washing machines should be used only when full and set to their most efficient settings to save water.

Question 53

How does customer pricing support water management?

Answer 53

Metering allows companies to charge for actual consumption, but this can raise concerns for households needing increased water for medical care. UK regulations aim to enhance competition and lower prices.

Question 54

What are two examples community level strategies of water management?

Answer 54

The Ice Stupa initiative, launched by the local government and engineers, involves creating artificial glaciers. Using a simple system of pipes, water is diverted from melting glaciers and sprayed into the cold air to form large ice structures, or stupas, during the winter.
-
These stupas can reach heights of up to 30 meters and store up to 15,000 cubic meters of water. By the time summer arrives, the ice gradually melts, providing a sustainable water source for agriculture and drinking.
-
This community-driven solution has enhanced water availability, supported local agriculture, and strengthened resilience against climate change impacts, significantly benefiting farmers in the region.
=====
In Kenya, sand dams have emerged as a successful community-level strategy for water management in arid and semi-arid regions. These structures, built across seasonal riverbeds, trap sand and create a reservoir for groundwater recharge. As rainwater flows into the riverbed, it settles behind the dam, where sand acts as a natural filter. The sand dam can hold water for prolonged periods, providing a reliable source of clean water for drinking and irrigation. Communities involved in the construction and maintenance of sand dams report improved access to water and enhanced agricultural productivity, with crop yields increasing by up to 300%. Organizations like the African Sand Dam Foundation have facilitated the adoption of this low-cost, sustainable technology, empowering local communities to combat water scarcity and foster resilience against climate change impacts.

Question 55

How does water purification support water management?

Answer 55

Despite its importance, over 1 billion people lack access to safe drinking water. Chlorine remains a common disinfectant, effectively eliminating harmful microorganisms.

Question 56

How does rain water harvesting support water management?

Answer 56

This practice aims to channel rainwater into the soil and conserve moisture for crops. Dams can trap runoff, while check dams help capture water and sediment during floods.