Unit 4

Question 1

The Hydrological cycle

Answer 1

Used to descrive the movemnet of water on the planet

Question 2

Storages and flows of the hydrological cycle

Answer 2

An understanding of storages and flows can be used to make more effective use of our water resources
SOLAR RADIATION DRIVES WATER CYCLE

Storages:
- oceans
- surfance waters, like rivers and lakes
- Ice caps and glaciers
- soil moisture
- water vapour and clouds
- groundwater
-organisms like plants and animals

Flows:
Transfromations
- evaporation
- transpiration
-evapotranspiration
- sublimation
- condensation
- melting
-freezing
-deposition

Transfers
-advection
-precipitation
-surface run off
- infiltration
- absorbtion
-percolation
-groundwater flow
-stream flow
- flooding

Question 3

Impact of Human activity in the hydrological cycle

Answer 3

An understanding of storages and flows can be used to make more effective use of our water resources
SOLAR RADIATION DRIVES WATER CYCLE

Storages:
- oceans
- surfance waters, like rivers and lakes
- Ice caps and glaciers
- soil moisture
- water vapour and clouds
- groundwater
-organisms like plants and animals

Flows:
Transfromations
- evaportain
- transpiration
evapotranspiration
- sublimation
- condensation
- melting
-freezing
-deposition

Transfers
-advection
-precipitation
-surface run off
- infiltration
- absorbtion
-percolation
-groundwater flow
-stream flow
- flooding

Question 4

Ocean circulation systems

Answer 4

Ocean circulation systems are driven by differences in temperature and salinity.
The resulting difference in water density drives the ocean conveyor belt, which
distributes heat around the world, and thus affects climate

Question 5

Is distribution of water equitable?

Answer 5

The supplies of freshwater resources are inequitably available and unevenly distributed, which can lead to conflict and concerns over water security.

Question 6

Access to water

Answer 6

750 million people do not have access to safe drinking water
Cause: poor infastructure and inadequate managemnet of water services is often to blame
- lack of knowledge and skills
- lack of finances
- lack of political will to makewater a priority

Question 7

Climate change and water scarcity

Answer 7

Climte change affects precipitation patterns
- some already water stressed areas in the mid latitudes ad dry tropics recieve less precipitation
- high latitudes will ecpeence more precipitatippn
- extreme weathers
- increased meltingrates = flooding
- rise in sea level contaminate surfce

Question 8

Water demand is expecte dto continue rise due to

Answer 8

• population growth
• increased standsrds of living
• more meat based diet
• industry growth
• urbanization

Question 9

Water stress

Answer 9

is when demand exceeds the available supply over a certain time period or when the quality of water restricts its use.

Question 10

Issues contributing to water stress

Answer 10

• overabstraction of groundwater at faster rate than being replenished
• abrstracion of surface waters
• pollution of water sources that increases clean up costs
• inefficient water use like poor irrigation, leakages, industy abuse, individual misusage

Question 11

Case study - water conflict

Answer 11

Ethiopian Grand Renaissance Dam

Ethiopia accapted not to let a hydroelecrtoc dam affect the flow of the Blue Nile into SUdan.

Question 12

Water scarcity

Answer 12

is when demand exceeds the available supply over a certain time period or when the quality of water restricts its use.

Question 13

Manging water resources solutions (just stae them)

Answer 13

1. Reservoirs (natural or artificial lakes)
2. Artificial recharge (used to increase water stored in aquifiers)
3. Rainfall haversting schemes (collection of precipitation)
4. Desalination (freshwater production out of sea water)
5. Water transfer schemes (from one river basis (surplus) to another in deficit)
6. Greywater (water clean enough to be used again)
7. Reducing demand (improved arguicultural processes, low flush toilets, campaings, education, increasing the cost of water..), legislation

Question 14

Difference between water stress and water scarcity

Answer 14

Water stress is when demand exceeds the available supply over a certain time period or when the quality of water restricts its use.

water stress can develop into water scarcity which is when the amount of water that can be physicllay accessed is lower than the demand.

Question 15

Reservoirs evaluation

Answer 15

Natural or artificially created lakes used to collect and store water. Created by damming rivers and flooding suitable valleys. Store water in periods of high rainfall to provide plentiful supply throughout the year.

ADV
- Generation of hydropower: Some reservoirs can generate electricity.
- Flood control: used to capture floodwater and reduce the risk of flooding in downstream areas.
- Navigation: The reservoir can provide transport route from one site another.
- Fisheries: Commercial fisheries have been developed in some reservoirs.
- Recreational, aesthetic and scenic value: such as water sports such as canoeing and water skiing. Picnic spots.
- Control of water quality: Sediment load of the water can be reduced in standing water.

Disadvantages
- Change of habitat: there is a change from a terrestrial to an aquatic ecosystem. scarce terrestrial habitats and species may be lost.
- Relocation of people: People may need to be moved out of an area that is to be flooded and relocated elsewhere. Whole towns and villages may be affected China’s Three Gorges Dam on the Yangtze River - displacement of 1.3 million people.
- Change to the flow of the water: Much of the water from the reservoir is diverted elsewhere e.g. to urban areas for industrial and domestic use. Can eventually pollute the river
- Loss of fish and mammal migratory routes:Dam walls can block the migratory route of some fish and dolphins.
- Sedimentation in the reservoir and loss of capacity: The sedimentation of particles from the water behind the dam wall reduces the holding capacity of the reservoir. In addition, this may not always be desirable for farmers downstream who rely on the nutrients in the sediments to fertilise their fields.

Question 16

Artificial recharge

Answer 16

used to increase amount of water stored in aquifiers. Widley used in Neatherlands.

Primary methods:
Ditch or Trench Recharge: Involves constructing a ditch or trench above an aquifer area to capture and accumulate runoff. The collected water gradually infiltrates the ground and percolates through permeable layers into the aquifer. This approach, while straightforward, can be costly due to land acquisition.

Borehole Recharge: Water is pumped from rivers or reservoirs directly into the aquifer through boreholes, which are drilled holes in the ground. Pumping directly from sediment-laden rivers may lead to borehole clogging, but using reservoirs to settle sediments before pumping into the aquifer can mitigate this issue.

Question 17

Rainfall harvesting

Answer 17

Rainwater harvesting involves collecting rain that falls on rooftops and storing it in tanks for various non-potable purposes like cleaning and gardening. This practice reduces the risk of flooding and soil erosion, is cost-effective, easy to maintain, and provides relatively clean water. However, if used for drinking, rainwater should be filtered and disinfected.

Question 18

Desalination

Answer 18

Desalinated water – seawater and other salty water that has been turned into freshwater – is used by cities and by industries, especially in the Middle East. The cost of this technique has dropped sharply, but it relies heavily on energy from fossil fuels and hence raises waste management and climate change issues.

Question 19

Water redistribution: water transfer schemes

Answer 19

Transport water from one river basin to another using pipes or canals. From water surplus to water deficit.

Grand, expensive projects.
Impacts
- lower water levels affecting habitats, such as wetlands and associated species.
- disruption in flow can affect fish and other biota living in the river.
- reduced amount of water may not be sufficient to meet the needs of local people.

Question 20

Use of greywater

Answer 20

water that is clean enough to be used again.

Greywater can be collected and used for toilet flushing and gardening. reduces the amount of wastewater produced and requiring treatment.

Communal systems for collection and treatment are often cost effective.

Physical treatment: filtration to remove large particles and disinfection to kill pathogens.
Biological treatment: involving either bacteria or wetland systems to utilize nutrients and filter particles from the water.

Question 21

Reducing water demand by..

Answer 21

Increasing water efficiency through improved technology and processes use:

• agriculture –> drip irrigation
• industry –> reuse water
• home –> low flush toilets, greywater

Public awareness campaigns
- shower instead of bathing
- more efficient washing machines & dishwaters

Economic incentives
- increasing water cost
- fines for wasting water
- Regulations that require all new buildings to be installed with low volume flush toilets, showers and greywater systems.

Question 22

Aquatic systems

Coastal waters and shallow seas tend to be productive, because:

Answer 22

In shallow water any nutrients that precipitate out are re-suspended by wind and currents.
River input brings in more nutrients.
Sunlight may penetrate down to the sea floor resulting in relatively high levels of light that drives photosynthesis.

Question 23

Energy efficiency of aquatic food systems

Answer 23

Aquatic food systems are often considered to be less efficient than terrestrial food systems:

Primary producers in aquatic systems receive less light than terrestrial plants because some of the incoming light is absorbed or reflected by the water.

Compared to terrestrial foods, humans generally tend to eat organisms from higher up in the aquatic food chain. Not all the energy is transferred from one trophic level to the next, hence the longer the food chain and the more transfers, the greater the energy loss.

Question 24

Managing fish stocks

Answer 24

Developments in fishing equipment and changes to fishing methods have lead to dwindling fish stocks and damage to habitats.

Unsustainable use of aquatic systems can be mitigated by:

• Use of quotas
  -Reduction of fishing boats
• Restrict boat size
• Limit number of fish
• MPA (marine protected areas).
• Exclusion zones (areas for fish to grow)

Question 25

Aquaculture. Then Open vs Semi-closed aquaculture systems

Answer 25

Aquaculture is the farming of aquatic organisms

2012, aquaculture contributed 66.6 million tonnes of fish and shellfish and 23.8 million tonnes of aquatic algae produced globally.
Aquaculture not only provides a vital protein source in many regions but provides a livelihood for millions of people. The FAO estimate that in 2012, over 18.8 million people were working within the aquaculture sector.

Open: Most popular. Farming organisms within natural aquatic ecosystem
Examples: fish cages, clam beds, oyster rafts

Semi-closed: More control. Abstraction of water to tanks or ponds on land. More expensive

Impacts:
Loss of habitat (by land clearance)
Increase in organic sediments (waste like fish feces and medicines)
Increase in nutrients –> algal blooms –> damage fish grills and can be toxic.
Spread of disease in dense cages
Predators can get entangled and caught in nets

Question 26

Sources of water pollution

Answer 26

Inland and coastal pollution:
- Domestic sewage: Source of pathogens like bacteria and viruses.
- Industrial discharge: Can include organic matter or toxic metals
- Agricultural run-off
- Urban run-off: Organic waste
- Land development: Buildings may involve forest clearance which increases soil erosion.
- Acid mine drainage: Rainwater percolates through either disused or active mines.

Marine based sources:
Outfall pipes (discharge material at dea)
Materials dumped at sea
Shipping activities (derrame de petroleo de Repsol)

Question 27

Types of aquatic pollutants

Answer 27

Organic pollution
Sewage effluent, farm runoff and food waste

Inorganic plant nutrients
If dropped in water, eutrophication happens (enrichment of waters with plants and nutrients, it becomes overly rich in plant nutrient and doesn’t allow for sunlight to reach the bottom of the lake or river.)

Toxic metals (toxic by interfering with essential cellular processes)

Synthetic compunds (like DDT they bioaccumulate)

Suspended soils (supress plant life by preventing light penetration)

Hot water (lower concentrations of oxygen result in increased stress level by organisms)

Oil (death of organisms. fur loses ability to repel water)

pathogens (health hazards)

Invasive species

light and noise pollution

Question 28

Assessing water quality

Answer 28

pH: indicate the acidity or alkalinity of the water. Extreme pH levels can harm aquatic life.

Temperature: Water temperature affects the amount of dissolved oxygen, and changes can stress organisms. Warmer water holds less oxygen than cooler water.

Suspended Solids: These are small particles in the water that can affect sunlight penetration, photosynthesis, and block feeding and respiratory systems of aquatic organisms. They can be measured by weighing collected residues or using instruments like turbidity meters or secchi disks.

Dissolved Oxygen (DO2): DO2 levels are essential for aerobic respiration in aquatic organisms. Low or no oxygen levels can lead to species loss, and oxygen levels can be affected by temperature and organic matter.

Biochemical Oxygen Demand (BOD): BOD measures the oxygen used to break down organic material in water. High BOD indicates pollution, as it reflects the amount of organic material that can be oxidized.

Metals: High concentrations of metals, whether from natural geology or human activities, can have adverse effects on the ecosystem and human health. Common examples include arsenic and mercury.

Biological monitoring:
Individual indicator species
Representative due to it being stationary
Biotic Index: Biotic indices are used to assess water quality based on the presence and abundance of specific aquatic organisms. High biodiversity indicates good water quality, while reduced species diversity may suggest pollution. Some species are sensitive to pollution (indicator species), while others are more tolerant.

Question 29

Water pollution management:
Domestic sewage system

Answer 29

Preliminary treatment: Screens to remove large objects that may damage equipment.
Primary treatment: Piped sewage allowed to settle within tanks in which solids are removed.
Secondary treatment: Biological process in which micro-organisms use unsettled organic waste as food source.
Tertiary treatment: Nitrate removal (ammonium ions oxidised) and desinfection to kill pathogens.

Question 30

Water pollution management strategies

Answer 30

reducing human activities that produce pollutants (for example, alternatives to current fertilizers and detergents)
reducing release of pollution into the environment (for example, treatment of wastewater to remove nitrates and phosphates)
​removing pollutants from the environment and restoring ecosystems (for example, removal of mud from eutrophic lakes and reintroduction of plant and fish species).

Minimize the amount of nutrients being released into the system by:
limiting production/use of detergents containing phosphates
alternative methods of enhancing crop growth
create buffer zones between agricultural land and water sources
regulating and reducing at point of emission
prevent animal waste from leaching into groundwater and rivers/streams

Treat the polluted area by:
pumping air into the water source
divert or treat sewage properly
dredge (dig up) contaminated sediments
physically remove algae blooms
reintroduce plant and fish species
pumping mud from eutrophic lakes

Question 31

Explain the process and impacts of eutrophication.

Answer 31

A major problem with the use of fertilisers occurs when they’re washed off the land by rainwater into rivers and lakes. The resulting increase of nitrate or phosphate in the water encourages algae growth, which forms a bloom over the water surface. This prevents sunlight reaching other water plants, which then die. Bacteria break down the dead plants and use up the oxygen in the water so the lake may be left completely lifeless

The main effects caused by eutrophication can be summarized as follows:
Species diversity decreases and the dominant biota changes
Plant and animal biomass increase
Turbidity increases
Rate of sedimentation increases, shortening the lifespan of the lake
Anoxic conditions may develop

Because of the high concentration of organisms in a eutrophic system, there is often a lot of competition for resources and predator pressure. This high degree of competition and the sometimes-high chemical or physical stress make high the struggle for survival in eutrophic systems. As a result the diversity of organisms is lower

Question 32

Evaluate pollution management strategies with respect to water pollution.

Answer 32

Changing human activities
Possible measures to reduce nitrate loss (based on the northern hemisphere) include the
following.
Avoid using nitrogen fertilizers between mid-September and mid-February when soils are wet and fertilizer is most likely to be washed through the soil.
Do not apply nitrogen just before heavy rain is forecast (assuming that forecasts are accurate).
Use less nitrogen if the previous year was dry because less will have been less lost. This is difficult to assess precisely.
Do not plough up grass as this releases nitrogen.
Use steep slopes for permanent pasture grass or woodland; use flat land above slopes for arable crops. This minimizes the greater risk of wash from steep land.
Incorporate straw – straw decay uses nitrogen, with up to 13 per cent less nitrogen lost – it also locks up phosphorus.
Direct drilling and minimal cultivation reduces nitrogen loss by up to a half. Less disturbance means less conversion of nitrogen to nitrate but straw has to be burnt.

Regulating and reducing the nutrient source
Public campaigns in Australia have encouraged people to:
use zero- or low-phosphorus detergents
wash only full loads in washing machines
wash vehicles on porous surfaces away from drains or gutters
reduce use of fertilizers on lawns and gardens
compost garden and food waste
collect and bury pet faeces.

Clean-up strategies
Once nutrients are in an ecosystem, it is much harder and more expensive to remove them than it would have been to tackle the eutrophication at source. The main clean-up methods available are:
precipitation (e.g. treatment with a solution of aluminium or ferrous salt to precipitate phosphates)
removal of nutrient-enriched sediments, for example by mud pumping
removal of biomass (e.g. harvesting of common reed) and using it for thatching or fuel.