Unit 4 Flashcards
Water budget
A quantitative estimate of the amounts of water in shortages and flows in the water cycle
The earths surface amounts to
70% water
Percentage of freshwater
2.6% of all water on earth
Percentage of ocean/salt water
97% of water on earth
How much freshwater in in polar ice caps / glaciers
68.7% approx
How much water is groundwater?
30.1% approx
Out of total water, how much is on the surface
On the earth’s surface in lakes, rivers and swamps this makes up 0.3% of all water
If all the water in the atmosphere rained at once
It would only cover the ground 2.5cm
Turnover time for….
A molecule of water to enter and leave part of the system is varied
Turnover times:
Rivers 12-20 days, Atmosphere 9 days, Groundwater 300y, ice caps 16,000y, ocean 37,000y
Water can be considered as
A renewable or non renewable resource depending on where it is stored
Energy from solar radiation and the force of gravity
Drive the water cycle, which drives the world’s water systems
The water cycle consists of….
Storages and flows of water between the various storages. These flows may be transfers or transformations
Transfers, when it stays in the same state:
Advection, flooding, surface run off, infiltration, percolation, stream, flow, and current
Transformations, when it changes state to/from liquid water
Evapotranspiration, condensation, freezing
Storages:
Oceans, soil, groundwater, lakes, rivers, streams, atmosphere, glaciers, ice caps
Desalination
Is very costly, and costly in terms of energy too, and is only possible in countries water stressed and near the sea. There is no point unless we find the technology to do this cheaply
A major issue with desalination:
Salt is a by product, and is usually returned to the ocean, sinking to the bottom ruining ecosystems
Even though we do have access to some freshwater
It can still be unsafe or highly polluted
Humans use freshwater for:
Domestic use (at home, drinking, washing, cleaning), Agriculture (Irrigation, for animals), Industry (mining, manufacturing), hydroelectric power generation, transportation (ships on lakes and rivers), marking boundaries between nation states (lakes/rivers)
Recommended fresh water
The world health organisation says humans should have 20litres each, Agenda 21 says 40, and much of the world have less or far more
40% of humans….
Currently live with water scarcity (this will increase)
Water scarcity is….
Not just a measure of how much water there is, but how it is used
Their may be enough water in each region….
But it is diverted for non domestic use
Agriculture uses water for irrigation and to provide for livestock
Usage rates here are tens of times higher than domestic use
As population expands
We need water to grow food, however the distribution is very uneven
Water is a major issue because of the added pressure of
Climate change, soil erosion, salinisation within international organisations
Many rivers….
Run through several countries (the Tigris/Euphrates within Iran, Iraq, Syria, The nile, the Danube river shared by 81m people and 19 countries) - If one country pollutes, the next country suffers
Wars have been fought over water and
This will continue as it becomes increasingly scarce
Sources of freshwater
Surface freshwater (rivers, streams, reservoirs, lakes) and underground aquifers
Aquifer
A layer of porous rock (holds water) sandwiched between two layers of impermeable rock (that does not let water through) - they are filled by infiltration of precipitation where the porous rock reaches the surface - this is only in limited areas
Water flow in aquifers is extremely slow
Horizontal flows can be as low as 1-10 metres per century, making them often used unsustainably
Many aquifers are also
Fossil aquifers - meaning the rechargeable source is no longer exposed at the surface so they are never refilled
Over 260 river basins
Are shared by multiple countries without legal or institutional agreements
Daily per capita use of water in residential areas:
350 litres in north america / japan, 200 in europe, 20 in sub-saharan Africa
Increased freshwater leads to two major problems
Water degradation, water scarcity - this means that water quality is deteriorating making it less suitable for human use
Global freshwater consumption
Is increasing as the human population is increasing, and the average ‘quality of life’ is also improving
Climate change may be:
Disrupting rainfall patterns, changing monsoon rains, causing further inequality of supplies
Underground aquifers are….
Being exhausted which means they can no longer be used which ultimately effects agriculture - buildings can also be damaged when soil is shrinking because the water is disappearing
Irrigation often causes
Soil degradation, especially in dry areas. Much of the irrigation water evaporates before it is absorbed by the crops, dissolved minerals remain in the top leader of soil making it too salty for further agriculture
Pumping rates from aquifers
Are generally too fast, causing exhaustion, making the wells unstable
Low water levels
In rivers and streams (EG: he colorado river is now a tiny stream, but can not be navigated when entering the Gulf of Mexico)
Slow water flow in the lower courses of rivers
Results in sedimentation which makes the already shallow river even more shallow, extending deltas further into the sea
Fertilisers and pesticides used in agriculture
Often pollute streams and rivers