Option A: Freshwater - Part 3: Water scarcity and quality Flashcards
Physical Water Scarcity
A country where water consumption exceeds 60% of usable supply
Economic Water Scarcity
A country that physically has sufficient water but requires storage and transport that they can’t afford.
Drought
Extended period od dry weather leading to extreme dry conditions.
ABSOLUTE DROUGHT: 15 days with less than 0.2mm rainfall.
PARTIAL DROUGHT: 29 days with daily rainfall not exceeding 0.2mm
Impacts of Drought
Reduced crop yields Increased animal deaths Increased illnesses Increased forest fires Ban on watering private gardens or washing cars
Water quantity
Rates of rainfall
Evaporation
Transpiration
River and groundwater flows
99% freshwater locked in ice and glaciers.
6.6 thousand cubic metres per person/yearly, reach 4.8 thousand by 2025.
1/4 of the world receive 3/4 of the rainfall.
2/3 of population live in areas receiving 1/4 global rainfall.
Water stress
Water supply per year is less than 1.7 thousand cubic metres
2016, 2.3 billion in water stress.
2025, 4 billion could be in water stress.
Water use over time
Population has tripled since 1922.
Water use has increased sixfold.
50% wetlands have disappeared.
1/5 freshwater species = endangered/exctint.
Depleting aquifers
Water tables are falling at alarming rates.
World water use to increase by 50% by 2040.
Water quality
4 million deaths each year from water-related diseases. Cholera, hepatitis, malaria.
Affected by sewage, fertilizers, pesticides, heavy metals and acids.
Port-au-Prince, Haiti: households connected to water system paid 1 dollar/ cubic metre while mobile vendors cost 5.5-16.5 dollars per cubic metre.
Outline the process and consequences of Eutrophication
Increased nitrogren and/or phosphorous carried in streams, causing nutrient enrichment.
This leads to algal blooms due to increased nutrient availability.
Increased algae and plankton = shade water = cut off light supply = oxygen starvation in water (anoxia).
Form ‘dead zones’ in coastal areas.
Loss of fertilizer = economic loss to farmers.
High nitrate concs. in drinking water = impacts health.
Dealing with Eutrophication
Altering polluting activities e.g. different fertilizers and detergents.
Restoring water quality by pumping mud from eutrophic lakes.
Reduce nitrogen added to fields near streams and lakes.
Reduce nitrogen added before heavy rains are forecast.
Irrigation
Water taken from surface stores e.g. lakes, dams, reservoirs, rivers, or groundwater.
Total flooding e.g. paddy fields = waste water, promotes water-logging, salinization, cheap)
Motors pump groundwater from aquifers faster than it is recharged.
Can reduce or increase water tables.
Decreases water quality.
Encourages salinization.
Reduce’s albedo by 10% due to dark green crops.
Changes precipitation, hailstorms and tornadoes.
Salinization
Irrigation leads to more water evaporation which leaves dissolved salts remaining in the soil.
Also increases chemicals such as chlorides and bicarbonates.
How is water used globally: agriculture, industry, municipal
All purposes: 3.7 thousand cubic km per year.
Agriculture: 70%
Since 1960 - water use for irrigation risen by 70%
Industry - 20%
Municipal - 10%
Pressures on water quantity and quality
Rivers no longer reach the sea.
Heavy pollution e.g. Ganges, Yangtze and Hwang He make 70% river water unsafe.
Contamination of agric, indust. and municipal waste.
Major loss of ecosystems due to salinization.
Depleting aquifers will take thousands of years to recharge.
Pop. growth pressure.
Grand Ethiopian Renaissance Dam Case Study
GERD is being built on the Blue Nile by Ethiopia.
Self-funded 4.8 billion.
170m tall and 1.8km wide.
Produce 6k megawatts electricity, doubling Ethiopia’s current output.
Egypt at risk - Nile provides nearly all of water.
Egypt claims 2/3 of water based on treaty signed with Sudan in 1959.
Annual water supply per person has decreased more than half since 1970.
March 2015 - Leaders signed declaration of approval for construction with no ‘significant harm’ to downstream countries.
Ethiopia - says they will use only power and water will flow downstream.
Large dam resevoir: to fill it will take 7 yrs and reduce Egypt’s water supply and electricity generation of Aswan Dam.
UN suggests using Nubian Sandstone Aquifer.
Sudan: sided with Ethiopia as the dam benefits them. Dam stabilizes + prevents flooding, consume more water and increase agriculture.
