Lecture 2: The changing water environment Flashcards
The “world water crisis”
- Humans have available less than 0.08% of all the Earth’s water.
- Over the next two decades our use is estimated to increase by about 40%, more than half of which to is needed to grow enough food.
- One person in five lacks safe drinking water now and the situation is not likely to get better.
WATER SUPPLIES: groundwater
Some extensive aquifers but especially in already wet countries
WATER SUPPLIES: rivers
- A major water source but again especially in wet countries
- Not in deserts or areas covered in ice
Water supplies: lakes and wetlands
● Lakes important for fisheries/aquaculture as well as water supply
● Wetlands important for filtration of water - quality
Water supplies: dammed reservoirs
● >36000 dams globally
● Problems for downstream (transboundary waters)
● Triggering earthquakes
● Impact of local climate
more on dams
Dams – the points in the landscape where water services are converted to money
Over 45,000 large dams in the world (>15 m and/or reservoir volume > 3M m3) holding back 15% of total annual global river runoff. (ICOLD/WCD, 2000)
- Dams contribute 12-16% to global food production (WCD, 2000)
- Hydropower accounts for 21% of world’s electricity supply (Renewable Global Status Report, 2007)
• Currently there are HEP projects under construction in about 80 countries, predominantly in South and
Central Asia, Latin America and Africa
Tropics : land areas draining into dams
There are at least 29,000 large dams between 40N and 40S
57% in Asia, 23% in South America, 12% in Africa, 6.5 % in Asia and the Caribbean, 1.3 % Australia, 0.2 % Middle East. 80% are in the largest countries (China, India, Brazil, South Africa, Zim, Mexico)
33% of land area between 40S and 40N drains into a dam
Europe: dams
2119 large dams in Europe
25.4% of the european land area drains into a dam
Water scarcity: physical and economic water scarcity
● Physical – climatically not enough water
● Economic – water quality and/or water infrastructure is too poor
Lack of access to safe drinking water
some countries in Africa and Asia more than 75 % without safe drinking water
NW India
● Intensive agriculture (wheat belt)
● Semi arid climate
● Heavily dependent on (fossil) groundwater
● Water tables falling
● Population and agriculture further increasing
● GRACE - August 2002 to October 2008, groundwater depletion was
equivalent to a net loss of 109 km3 of water (17.7km3/yr)
Water quality (mining) - Peru
● Large mines important to economy (e.g. Yanacocha - gold)
● Release effluent into rivers (and groundwater) containing e.g. cyanide used in processing
● Many people downstream (not happy – civil unrest)
Water quality
● Water quality = water availability (for a purpose)
● Quantity and access can be high but if quality is not sufficient then
water scarcity can still exist
● Countries like Colombia have a lot of water but to what extent is it all
usable without expensive water treatment?
% of water that is human impacted
At the national scale the downstream decay of influence away from agricultural and urban areas is clearer.
We might expect the human influence to be reflected in higher sediment loads, organic and inorganic contaminants, incl. pesticides and fertiliser etc.
This decay results from the dilution of human influenced water with runoff from less influenced areas
% of water supply to urban areas that is human impacted
At the local scale supply to urban areas is influenced by water diversions, aqueducts, transfers etc. for which there are no data globally.
But, if we assume that rivers running into urban areas supply those areas with water then we can map the heavily impacted urbanisations
Many of these cities will use intensive water treatment to offset these impacts
