ESS - Topic 4 Water and Food Production

Water budget

A quantitative estimate of the amounts of water in storages and flows of the water cycle

How much freshwater is available to us on the Earth?

3% of the Earth’s water, Less than 1% of water available for us to drink

How much of the Earth’s water is found in the atmosphere?

0.001%

Water turnover time

Time taken for a molecule of water to enter and leave that part of a system

Why may water be both a renewable and non-renewable resource?

Depends on where you’re taking this water from.

Non-renewable: polar ice caps,ice in permafrost,oceans,groundwater... —> Large turnover time --> takes a long time to replenish (won’t replenish within our lifetime)
Renewable: biological water,rivers,atmospheric moisture,upper soil moisture —> Small turnover time --> replenish faster than we need it so it can balance out to how much we use

System

A set of interrelated parts working together to make a complex whole

Describe the Water / Hydrological Cycle in as much detail as possible:

Hydrological Cycle is a system --> Material and energy undergo transfers and transformations

1. Water in the ocean is heated by the sun (whole system driven by energy from sun)

2. Water evaporates to form water vapour

3. As air rises it cools --> water vapour begins to condense to form clouds

4. When clouds get too large and water droplets get too heavy --> fall as rain or snow

5. Water can then...

   1. Run-off: Run off surface and go into the river --> ocean

   2. Infiltration: go into the ground --> percolation (through the ground) --> ocean

   3. Trees absorb ground water --> transpiration and condensation --> repeated cycle

      (evapotranspiration)

How is water stored in the hydrological system?

• Oceans

• Lakes, rivers

• Ice-caps

• Atmosphere

• Clouds

• Aquifers

How is water transferred

• Advection (wind)

• Flooding

• Surface run-off

• Currents

• Stream flow

• Infiltration/percolation

How is water transformed

• Transpiration (water --> vapour)

• Freezing (water --> snow)

• Condensation (vapour --> water)

What are the two main reasons which water is withdrawn from freshwater supplies?

Thermoelectrical (41%), Agriculture Irrigation (37%)

Give 3 things humans do which can alter the flow rate or the pathway of natural water flow:

1.Building canals (artificial water ways) —> Direct water in different pathways back to sea to stop towns from flooding + irrigate crops

2. Road building —> Build tunnels under roads --> direct rivers to stop roads from flooding

3. Dams, reservoirs and dykes —> Slow the water

ALL: change the direction(route), storage, and speed changes to water flow

Why may we divert rivers?

• Create new habitats (e.g. wetland) --> little impact on the original river

• Create a reservoir

• Avoid flooding sensitive areas

Why is the Aral sea being depleted?

Depleted due to intense irrigation, Used up all the river flow that goes into the sea to irrigate farmland --> no river flow into the sea

Why is Ganges Basin flooding more?

Due to deforestation --> no vegetation to absorb water --> more flooding

Ocean current

Movement of water vertically and horizontally in a specific direction (found on surface and in deep water)

- Current: convection of water (Warm water rises and cold-water sinks --> change in temp causes movement of water around world)

What do currents move around the planet, why is it important?

• Vital role in moving/distrubuting energy

• Key in understanding energy changes in our atmosphere

What is a surface current and what effects it’s direction?

• Upper 400m of water

• Affected by wind (Gulf stream of wind across the Atlantic) and Earth rotation deflects them --> circular motion

What is a Deep-Water Current?

Thermohaline currents

• 90% of currents

• Create oceanic conveyer belt —> Vital for moving warm and cool water around --> driving our climate

Two factors affect the density of water

1. Concentration of salt (more salt = denser)

2. Temperature (colder = denser)

Describe how an ocean current is created

1. Warm water holds less salt than cold water --> less dense and rises

2. Cold water more dense --> sinks

3. Warm water rises, cold drawn up from depths to replace (upwellings)

4. Risen cold water replaced by warm water which sinks (downwelling)

5. Water circulates

Cold Ocean Current

Run from poles to equator

Warm Ocean Current

Run from equator to poles

Why are coastal areas often more stable

Water has High specific heat capacity —> Needs to gain or lost a lot of energy to change its temperature by 1C

• Coastal areas (near water) stable —> temperature doesn’t change often

Why may the mid-Atlantic Current be slowing?

Climate change

• Ice caps in Greenland melting --> Adding fresh water --> dilutes saltiness --> less dense --> stops water from sinking --> no convection --> ocean current slows/stops —> Less water returning to Gulf of Mexico

High Northern Atlantic Oscillation Years

• Lower pressure over Iceland

• Higher pressure in Azores

• Winds that blow from East to West (westerly winds)

  Warm weather comes straught from America to Europe Therefore...

• Mild winters

• Cooler wetter summers

Low Index Years

• Less pressure differences

• Less direct wind from East to West (Less westerly winds)

Goes up to Greenland and Iceland and then Europe Therefore...

• Colder winters

• Heat wave summer

Southern Oscillation during normal years

Wind drives higher pressure in the East Pacific than the west --> Trade winds blow west for most of the year ---> warm water blows westwards --> cold water moves upwards (upwelling) --> bringing nutrients up

El-Nino years

Higher air pressure in West pacific than the East --> Trade winds blow east (reverse) --> warm water blows eastwards (coastline of south America) --> warm water sinks (downwelling) --> no upwelling

Effects of El-nino

1. Anchovy populations

   • No upwellings (humboldt current) --> lack of nutrients from the deep water

   • anchovy stock collapse (nothing to eat)

   • food chains collapse

   • loss of sea birds

2. Humans

   • storms and flooding in Peru (winds coming in towards peru)

   • destructions along the coastlines

El-Nino effect global environments

• Drought in Africa, Australia and Indonesia (forest fires)

• Heavy storms in California, central Europe, east Asia

• Absence of monsoons in India (needed for food production)

• increases the Impacts of climate change

• elnino can be AMPLIFIED from human activity

How much water is used for agriculture

70% of freshwater

Should we punish these countries for wasting water?

Countries uses more water for agriculture --> agriculture then shipped and used in other areas (due to land)

e.g. South Asia produce food that will be used in other regions

Why is chicken meat more sustainable than beef meat production?

Save a huge amount of water (plants need irrigation) —> Less water in the process of producing chicken (feeding, food)

How does water stress differ around the world?

Uneven distribution
Low water stress: colder, snowy areas (Russia)

High water stress: around the equator (more exposure to the sun)

Why is water pollution important when considering water availability?

Water doesn’t always just flow through one river

•  e.g. Dirty Danube River (Flows through multiple countries in Europe —> As it flows --> gets gradually more polluted)

• Water stress is not only about availability BUT ALSO quality of water (depleting and polluting)

Aquifer

Layer of porous rock between two layers of impermeable rocks

• e.g. artesian aquifer between solid rock, clay (impermeable rock)

• Filled by infiltration by precipitation where rock reaches surface (recharge site)

Why may aquifers (see image) take a long time to refill and replenish?

• Small area for water to infilitrate (recharge site)

• Very slow water recharge/flow

• Human use it quickly --> cannot recharge fast enough --

  > unsustainable --> eventually run out! (fossil aquifer: recharge source no long exposed to surface)

Why is water getting more limited in supply due to our over usage?

• Climate change (Disrupting rainfall patterns --> less and uneven)

• Slow river flow due to sedimentation (surface run off)

• Due to surface run-off

• Underground aquifers exhausted (Due to agriculture)

• Contamination of freshwater

• Irrigation (Solid degradation: irrigated water with salts evaporates --> leaves behind minerals in top soil layer --> salinization of soil)

• Eutrophication

• Warm water (pollution!) from power plants o Less oxygen in the water

How can we increase freshwater supplies in some areas?

• Build more reservoirs a. Store more rain

• Desalination

• Rainwater harvesting system

• Artificially recharge aquifers
  a. Build reservoir above recharge points --> allow aquifer to be directly recharged

How can we reduce domestic use?

efficient devices, Closed water systems to wash cars, Grey water recycling

How can we reduce agricultural use of water?

• Irrigation reduction (Trickle system (slower) > spraying (high levels of evaporation loss)

• Pesticide reduction (reduce degradation of water) —> organic fertiliser (manure) —> Releases nutrients slowly --> prevents excess nutrients from getting into water

• Biological controls over pesticides

• Remove pollutants from industrial wastewater

• Prevent warm water release from power station

Why is warm water released from power stations a problem?

Warm water (type of pollution) holds less oxygen --> bad for marine organisms (cannot respire)

Why did water become a big issue in Israel?

Lack of water due to

• Population growth

• Improved quality of life
  ▪ People in Israel using dishwashers, showers...

• Less rainfall due to climate change o Irrigation

• Water disputes with Jordan

Why is desalination an expensive process? How is it being made more sustainable?

High energy usage

• Distillation and reverse osmosis require large amounts of energy (high

  temp/pressure) --> expensive!

More sustainable with renewable energy

Why is a higher biodiversity important for ecosystems?

High Biodiversity = high stability and resilience

Where is 50% of productivity in marine habitats and why is this the case?

50% of productivity above continental shelf (15% in area)

• Upwellings pushed up continental slope --> rich in nutrients

• Exposure to light can reach shallow shelf --> plants/algae can photosynthesise = high productivity

Who owns the continental shelf? (define)

Extension of continent under sea creating shallow water, 80km wide, belongs to country which it extends from

Fisheries

Fish harvested in some way includes capturing of wild fish, aquaculture and fish farming.

Why are more people eating fish?

High in protein, contains vitamins, low in saturated fats = healthy diet

How do we know that fisheries are as exploited as possible now and cannot provide more fish for us?

• 70% of fisheres at limit (decline or too low to recover)

• Even with better technology --> catch no long increasing (levels levelling off)

• Catch cannot be increased with more demand

• Capture fisheries levelling off --> aquaculture increasing (artificial fishing)

How can fisheries be made more sustainable?

Fishmeal

• Use trimmings and scraps that would normally be wasted --> fish food

• Livestock/poultry waste used as food

Why is turning rice fields into fisheries a good idea?

• More environmentally friendly

• Fish can survive and eat in there --> produce waste --> waste acts as a fertilizer for the rice

Why is shrimp or salmon a very unsustainable method of growing fish populations?

•  Fed on fishmeal or fish oil from wild fish

• Mangrove swamps replaced by fish farms

  ▪ 2/3 mangrove swamps in Philippines have been replaced by fish farms

•  Causing...

  ▪ Habitat loss
  ▪ Pollution (feed, antifouling agents, antibiotics, medicines)
  ▪ Spread of diseases
  ▪ Genetically modified species escaping --> interbreeding in wild —> Out competition of native species

Why are mangroves important?

• Prevents flooding/storm surges

• Cleaning water

• Fighting impacts of climate change

Why is wild fishing no longer sustainable?

Catch becomes smaller as no time given for them to mature

Reason: we are too good at fishing!

o GPS to locate fish
o Larger fishing fleets with better freezing
o Spend longer at sea
o Indiscriminative fishing methods (bycatch)
o Clear cutting of seabed by trawlers (destroying habitat)

How is caught fish used?

15% consumed by humans, 25% fishmeal in aquaculture, 50% lost as bycatch —> Discarded and thrown away

tragedy of the commons

Resource that people perceive as common to everyone --> everyone exploits it --> over exploited in competition --> population crashes

Internal waters

next to country coastline, foreign ships cannot travel, country sets up own laws and regulates use

Territorial waters

Foreign ships can travel through but CANNOT spy/fish/pollute

Contiguous Zone

state can patrol smuggling or illegal immigration activities, fishing is allowed

Exclusive Economic Zone

state has sole rights to exploit all natural resources, foreign nations can go through

What is MSY and what does it mean? (fisheries)

Increase in natural capita that can be exploited without depleting original stock of ability to replenish. (how much you can remove without permanently depleting the resource)

• Fisheries = amount of fish and what size in any harvest to not deplete future years

• Specific carrying capacity – amount the environment can contain Depends on...

  • Reproductive Stategy

  • Longevity

  • Resources of ecosystem

Why is MSY often not actually sustainable?

• Population dynamics normally predicted on a model --> difficult to calculate precise population sizes

• Estimates = previous experience

• Difficult to model age and sex ratio

• Disease not accounted for

• Pollution not accounted for

therefore —> optimal sustainable yield

water pollution

Contamination of bodies of water by pollutants either directly or indirectly

List the different types of water pollution:

1. Anthropogenic (we produce it) or natural (e.g. animal natural waste into water)

2. Point source or non-point source

3. Organic (manure) or inorganic (chemicals)

4. Direct or indirect (react with other chemicals)

Freshwater pollution source

agricultural run-off, sewage, industrial and domestic discharge

Biochemical Oxygen Demand

Amount of dissolved oxygen required to break down the organic material in a given volume of water through aerobic biological activity of microorganisms

BOD Scale

Water polluted --> lots of organic matter --> oxygen breaks down

• Polluted --> LOTS of oxygen to break down (100 or more)

• Less polluted --> less oxygen needed to break down (1-2)

biological indicator

Living organisms whose presence/absence gives information about an ecosystem

How can we use invertebrates to identify pollution in freshwater rivers?

• Depend on type of species —> how polluted

• Sensitive to oxygen concentration

• Oxygen levels change due to aerobic bacteria using oxygen (respiration) to break down organic matter (sewage)

• low pollution is stone fly, high pollution is tubifex worm

Pollution vs oxygen

More pollution --> bacteria use MORE oxygen to break down matter --> O2 goes down (vice versa)

High oxygen = low pollution

Low oxygen = high pollution

eutrophication

The addition of additional nutrients to body of water --> causes a change in the aquatic system

Leaching

when nutrients in fertilisers dissolve in soil water and enter aquatic ecosystems

What are the sources of the potential nutrients into freshwater?

• Detergents

• Fertilisers

• Sewage

• Drainage from intensive animal breeding

• Topsoil erosion (take nutrients into the water due to surface run-off)

Explain Eutrophication

1. Nutrients enter the water from sources such as fertiliser, sewage, detergents, etc.

2. Increase in the concentration of nitrates and phosphates in water

3. Increase in the growth of algae --> algal bloom

4. Blocks out sunlight so plants below cannot photosynthesise --> oxygen depletes

5. Plants and organisms die --> bacteria decompose it via respiration and uses up more oxygen

   --> oxygen depletes

6. Oxygen depletion --> aquatic organisms that require oxygen die (unable to respire)

impact of on biodiversity for eutrophication

• Oxygen deficient water --> loss of biodiversity (dead zones)

• Death of higher plants

• Death of aerobic organisms

• Increased turbidity (cloudy/muddy)

Three methods to mitigate

Alter human activity, regulate release of pollutant, restore habitats and ecosystems

How can we alter human activity to reduce water pollution?

• Adopt alternative lifestyles (use less chemicals, organic materials)

• Protesting

• Reduce, recycle, reuse

• Use alternative technologies

How can we regulate pollution control?

• Set standards in countries

• Laws and regulations to reduce the use of pesticides

• Ban chemicals in certain products

How can we restore ecosystems?

• Extract and remove pollutant (algal blooms)

• Replant and restocking the biodiversity

Direct measurements of water pollution

oxygen probe, pH probe, temp probe, turbidity meter, measuring ABIOTIC FACTORS using a probe

• tech more accurate, faster, cheaper

• Deduce risk of contact with pollutant

• data can be used after

Indirect measurements of water pollution

biological oxygen demand (BOD)

amount of oxygen required to breakdown the organic material in a given volume of water through aerobic biological activity of microorganisms (CHANGE in oxygen OVER TIME)

Indicator species

living organisms whose presence/absence gives information about an ecosystem

creates a biotic index which allows us to assess the impact of pollution on a community

e.g. invertebrates !!!