IB ESS SL 4.2 Water Access Use and Security Questions

water resources are polluted/contaminated;
water resources are used up/rate of water consumption is greater than the rate of replenishment;
global warming/climate change/drought;
water used for purposes such as mining/industry /agriculture;
financial resources to source water (eg boreholes/reservoirs);

Rainwater harvesting (4 max):

Pros:
a. Low cost supply of water;
b. Low environmental impact/low technology;
c. Renewable supply / reduces use of potable water;

Cons:
d. Quantity very limited for agricultural purposes;
e. Weather/climate dependent;
f. May contain atmospheric pollutants / isn't generally potable;

Desalination (4 max):

Pros:
g. Vast supply of sea water available;
h. Produces potable water;
i. Independent of climate/precipitation;
j. Provides water security/independence;

Cons:
k. High cost supply:
l. Limited to coastal location;
m. Disposal of leftover salt;
n. Requires excessive energy supply;
o. Produces significant noise pollution;

in many countries water scarcity will increase / higher percentages of water present will be extracted;
changes are usually greater in the mid to lower latitudes/nearer the equator (than the poles);

a. campaigns to educate public to reduce water use e.g. by encouraging change in individual behavior to reduce water use;
b. promotion/use of water saving appliances/devices;
c. replacing lawns/yards/grass with drought-tolerant gardens/dry-land gardening;
d. recycling/reuse of water/grey water;
e. use of rainwater capture/water butts/barrels to collect rainwater;
f. improvements in infrastructure to reduce water leakage/losses;
g. imposing water usage quotas/water restrictions;
h. installation/use of water meters to encourage less water usage / water tariff rates that increase as use increases / increase in water prices;
i. change from water intensive industries to non-water intensive industries e.g. service-based businesses (within urban areas);
j. promote the use of public swimming pools instead of private/domestic pools;

improved irrigation efficiency eg drip irrigation;
use crop cultivars that require less water (eg drought resistant seeds/GMOs) / replace high stress crops (eg cotton) with low stress (eg oats);
improve water catchment/storage with dams; reservoirs;
install desalinization plants in coastal areas;
plant cover crops/use terracing (to reduce evaporation/run-off losses);
use salt-tolerant crops to exploit available sea-water/saline soils;

Cons:
a. people relocated from the area to be flooded / loss of communities/villages / loss of livelihoods in the area;
b. loss of habitat to area that was flooded / loss of habitat to construction of the canal/pipeline that carries the water from the reservoir to Beijing / destruction of habitat caused by building of road to the construction site;
c. reduction in flow into the Yangtze river affecting wildlife/fish populations/human settlements / loss of water for the Shanghai area;
d. dam blocks fish migration;
e. dam disrupts/reduces flow of sediments downstream;
f. (weight of water in dam) can trigger seismic movement/earthquakes;
g. increase in insect vectors/water-borne diseases (e.g. bilharzia/malaria);
h. rotting vegetation in dam can release greenhouse gases (methane and carbon dioxide) / it is energy intensive to build and equipment used release greenhouse gases / $\mathrm{CO}_{2}$;
i. potential loss of water from canals/dams due to evaporation / potential loss of water from canals due to long distance of transfer to Beijing ( 1200 km );
j. it is expensive to construct / pipelines will require continual maintenance which is expensive;
k. over-dependency on a single source could be an issue e.g. drought in the Shanghai region;

Pros:
l. production of hydroelectric power / generates electricity sustainably;
m. provides flood control;
n. provides water supply for Beijing residents / improves availability of safe water / decreases water scarcity;
o. water available for irrigation;
p. water available for industry;
q. avoids use of groundwater/polluted surface water;

Balanced conclusion (example):
While the benefits to Beijing in terms of addressing water scarcity would be enormous, the environmental impacts (e.g. of loss of habitats) and social impacts (e.g. loss of villages and communities) of increasing the dam size would outweigh the benefits.