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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



Oceans, soil, groundwater, lakes, rivers, streams, atmosphere, glaciers, ice caps



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



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



Release pollutants into the surface water bodies


Electricity plants

Release warm water into rivers which holds less dished oxygen than cold water, allowing aquatic organisms to take their oxygen from this water and fish are negatively affected. Warm water outflow from power stations changes the species composition in the water


Solutions to increase freshwater supplies

Reservoirs, redistribution, desalination plants, rainwater harvesting systems on small and large scales, artificially recharging aquifers, reduce domestic use of freshwater by using water efficient showers/dishwashers/toilets, wash cars in closed system car washes, gre water recycling, reduce amount of pesticides regulate max temperates of released cooling water, use highly selective pesticides, biological control measure, remove pollutants with water treatment plants, replace chemical fertilisers with organic ones, reduce the need for irrigation


Reservoirs advantages

Keep more stock of water, companies are keen to use them, they tackle temporary shortages, there are environmental agency proposals to improve the efficiency and have them approved


Reservoir disadvantages

Plans are hard to put forward, they take a long time to plan and then build, huge investment, hard to predict the amount of future resources we need in the future, history of rejection


Drinking salt water / desalination advantages

Simple (for UK as they are an island country), provides safe water for a large amount of people and homes


Drinking salt water / desalination disadvantages

Costly, something would have to be done with the leftover sale, it could endanger marine life, by building desalination plants, there would be a large carbon impact on the environment


Drinking sewage water (grey water) advantages

Extra costs would only be required in the diversion process, long term, it would be pure water v


Drinking sewage water (grey water) disadvantages

Negative public perception because of quality, cost of cleaning


Persuade people to use less water advantages

Simple for the average person to do, Almost automatic, people want to help the environment, managing demand could be the solution


Persuade people to use less water disadvantages

Some people would not take part, large cost of a marketing campaign


Compulsory water metres / raise in price advantages

People will become more aware and therefore hopefully use less, If people have large sources such as a swimming pool - it is right that they should pay for it, the government already favours this solution


Compulsory water metres / raise in price disadvantages

Does not always have the intended effect, true value of water is not reflected in pricing - some people will use pay to use more water, domestic water usage is considered a basic human right


Make companies fix leaky pipes advantages

Plugging holes is a better economic alternative to replacing them, it would save a very large amount of water


Make companies fix leaky pipes disadvantages

Urban trees could die


Build a cross country pipeline advantages

There is more rainfall in the north so it could be easily transferred, it is a long term solution, it would optimise the use of water resources


Build a cross country pipeline disadvantages

Risk of leakage, costs of construction are very large


Stabilise or move population advantages

Immigration would reduce risk of water shortages in some areas, it would also help what the pressure brought by infrastructure, it is an alternative to reducing immigration if people are willing to cooperate


Stabilise or move population disadvantages

People will not understand, people will be unwilling, this might cause further issues such as the current housing crisis, people might become even more greedy so the demand would not decrease



Clearing a beg or harbour using a dredge which is a metal cage which captures all pollutants and fish hiding underneath the surface of the bed (in the sand)


Bottom trawl

Trawling is essential spreading a wide fishing net across a seabed to catch certain fish or aquatic animals (this could be benthic or demersal trawling)


Midwater trawl

Trawling or net fishing at a depth higher than the bottom of the ocean - contrasting with bottom trawling


Purse seining

Seine fishing involves a dragnet that hangs vertically in the water, with the bottom being held down with weights, and the top being buoyed with floats. They can be deployed from the shore, a beach seine, or boat



A netting system where floats hold nets in a line, and weight pull down creating a wall. A large net is at the bottom so when it is brought up, it encompasses all the captured fish


Handline and Jig

Environmentally friendly with low bycatch. The handline is reeled mechanically when in deep water, and the jig is the hook attached to the line and it moves mechanically to lock in the prey. This is done at night as the fish are easier to lure (closer to the surface)



A longer version of a fishing line, stretching 50 mines. Attached are evenly places small fishing lines with bait. It can be deep below the surface or right on top. By sinking it lower or using different hooks, bycatch is avoided as on the surface seabirds could be attracted to the bait



Trolling is when one or more lines baited are draw the through the water, maybe behind a moving boat, or slowly winding the line from a static position, or sweeping the line from side to side. It is used to catch pelagic fish like salmon



A line or multiple towed by a boat, with species following moving bait. When the bait is grabbed the lines are relied in, so there is no bycatch as fisherman let go of unwanted species


Traps and Pots

Small contraptions made in order to capture a small amount of aquatic animas such as crabs, shrimp, or smaller fish. Floats are used to alert fisherman where the traps ad pots are



A traditional method for large species, and only used by skilled fisherman, then thrust or shoot a long harpoon made of wood or aluminium to catch it and haul it aboard. There is no bycatch as the harpooners can see the species before targeting them


A food chain

A singular chain of what eats what


A food web

A more complex relationship with a series of food chains


Maximum sustainable yield

The maximum catch or take that can be harvested from a stock over an indefinite period of time


Complications of the calculation of maximum sustainable yield

Changes in carrying capacity over time, policies, depending on the current size of population


Maximum sustainable yield formula

Carrying capacity / 2



The process of water transforming from a liquid into a water vapour



Water extracting from clouds and entering the earth, landing on its surface. This is in the form of rain, hail, snow, or sleet



The process between precipitaron and storing, when flows deepen into the aerated soil below the ground because of gravity



Flow of water travelling in a horizontal direction within a layer of soil. It usually takes place when the soil is already completely saturated with water, flowing until it reaches an ocean


Surface runoff

When water moves over land surface and travels into the ocean



Essentially a similar process to evaporation but is carried through plant leaves, changing into water vapour and becoming exposed to the earth's atmosphere



A combination of the processes of evaporation and plant transpiration from land and ocean surfaces, into the atmosphere



The process of snow and ice transforming into water vapour within the atmosphere, without melting into water



Any water thae has evaporated over either land or water could not precipitate



When water vapour in the air is turned into liquid. It also forms clouds within the water cycle. The opposite of evaporation



Permeation of a liquid into something by filtration



The process of surface water entering the soil below ground level ????


Marine ecosystems

Oceans, mangroves, estuaries, lagoons, coral reefs, deep ocean floor, are very biodiverse so have high stability and resilience


One half of marine productivity

Is in the costal regions above the continual shelf


There is hardly any marine productivity

In the deep oceans where light does not reach as only dead organic matter and food sources are chemotrophs descend from above


Continental shelf

The extension of continents under the seas and oceans, where the continental shelf exists it creates shallow water - it has 50% of ocean productivity but is 15% of its area, countries can claim it as theirs to exploit and harvest, the water is inch or nutrients, light reaches the shallow seas so producers can photosynthesise



Single called organisms that can photosynthesise and are the most important producers in the oceans, producing 99% of primary productivity. They float in the sea



Also float in the sea, they are single felled animals that eat the phytoplankton, and their waste, and between them, these organisms support the complex food webs of oceans


Marine organisms can be classified as:

Benthic - living on or in the sea bed
Pelagic - Irving surrounded by water from above the sea bed to the surface


Human impact on the water cycle:

Withdrawals, (for domestic use, irrigation, agriculture, and industry) discharges (adding pollutants to water), Diverting rivers to avoid flood damage, Changing the speed at which water can flow and where it flows


Flash floods occur

When rainfall or snow elf cannot infiltrate the social and runs off the surface. This could be due to land being hard baked in hot, dry areas, but more and more due to impermeable surfaces in cities


Major changes caused by humans

Aral sea - lowering the sea's level, run off from urbanised areas causing local flash flooding, Ganges Basin flooding absorbed by vegetation


Deep water currents

Also called thermohaline currents, make up 90% of ocean currents and cause the oceanic conveyer belt


Importance of water:

Moves continuously, keeps us warm, moderates climate, makes food, keeps us alive, removes and dilutes wastes and pollutants


Human activities such as agriculture, deforestation, and urbanisation

Have a large effect on surface runoff and infiltration


The ocean circulatory system

Influences the global distribution of water and the overall climate


Solar radiation

Drives the hydrological cycles


Surface currents

Are moved by the winds and the earth's rotation deflects them and increases their circular movement


Ocean currents

Movements of water both vertically and horizontally. They move in specific directions and some have names, they are found on the surface or in deep water


Factors of deep water currents:

They are due to differences in water density caused by salt/temperature, warm water holds less salt than cold water so is less dense and rises, cooled water holds more salt, is denser so sinks. When warm water rises, cold has to come up from the depth to replace it, these are upwellings. When cold rises, it needs to be replaced by warm in downwellings. Water circulares


Ocean circulation systems are driven by

Differences in temperature and salinity - the different in water density drives the ocean convenir belt which is responsible for distributing heat around the world - affecting climate


3 things to remember with the water cycle:

Heat rises, if you have high salt concentration, water will always move towards water with low salt concentration, the sun is driving the whole system