Water Use http://ih-igcse-geography.wikispaces.com/1.6.+Uses+of+water http://ih-igcse-geography.wikispaces.com/1.7.+Water+Use
This week we are going to look at… • Water sources and how much accessible fresh water there is • The causes of water shortage • And to look in detail at one country where water requirements are rising – our first official case study!
The Unequal Distribution of Water • Globally • With 70% of the planet covered in water, it is hard to imagine that there may be problems with the world's water supply. But take a look here:
The Unequal Distribution of Water : Globally • Less than 3% of the earth's water is fresh and most of this is difficult to obtain. • At the same time, water supplies are very unequal on a global scale, depending on the differences in climate, and the balance between the amount of precipitation on the one hand and the loss of moisture from the soil, rocks and plants, known as evapotranspiration, on the other. • In much of the Middle East, evapotranspiration is higher than precipitation, creating a water deficit. • In North-West Europe, the opposite is the case and we benefit from a water surplus.
The Unequal Distribution of Water : Locally • Distribution of water on a local scale is not just a result of nature, however. • People who live upstream of a river may use up or waste water at the expense of people who live further downstream. • Even in arid areas, there are richer people who have all the water they need. • Meanwhile, poorer communities have the greatest difficulty in having enough water. • In water-scarce western India, powerful irrigation pumps work twenty-four hours a day, while poorer women find their drinking wells run dry. • Therefore water shortages are often as much to do with inequality amongst people as they are to do with the natural conditions of an area.
Wasted Water • For thousands of years, people have been developing ways to extract water from rivers and the groundwater supply to irrigate the land. • Large-scale development projects using mechanical pumps have made irrigation much easier but there are signs that they can create as amny problems as they solve. • Some rivers have been reduced to a trickle by the time they reach the sea. • In parts of China, India, Mexico and Yemen, water tables are dropping by a metre a year as people pump up water from underlying aquifers.
To make matters worse, scientists have discovered that only 15% of the irrigation water is actually taken up by crops. • The rest either evaporates or escapes through broken pipes and unlined channels. • What could be the problem here? An irrigation channel in Tamale, Ghana
This inefficient management of water can lead to the twin problems of water logging and salinisation. • When too much water flows over the land it can become waterlogged, and crops quickly rot and die. • Salinisation occurs when the natural salts contained in irrigation water seep into the ground and build up in the soil, making it too salty (saline) to grow crops. In the Indus valley in Pakistan, salinisation is a major problem for farmers. Hot temperatures cause the water in the soil to evaporate. As a result, the salts are left behind and ruin the farmland.
A couple of solutions • One is a very low tech method of overcoming the problem of wasted water • The other can and is used in developing as well as developed countries
What it is like – the details • The temperature gets as cool as 140C in the winter season • And as hot as 420C in the summer • (when would that be? which side of the equator is it?) • The rainfall varies from between 400mm and 700mm and falls from June to September • Savannah is grassland with some trees and shrubs
A local solution – the Zaï System • Pits are dug during the dry season from November until May and the number of Zaï pits per hectare varies from 12,000 to 25,000. • After digging the pits, organic matter is added at an average, recommended rate of 0.6 kg/pit • After the first rainfall, the matter is covered with a thin layer of soil and the seeds placed in the middle of the pit.
The advantages of Zaï are that it : • (i) captures rain and surface/ run-off water; • (ii) protects seeds and organic matter against being washed away; • (iii) concentrates nutrient and water availability at the beginning of the rainy season; (iv) increases yields; and • (v) Reactivates biological activities in the soil and eventually leads to an improvement in soil structure. • The application of the Zaï technique can reportedly increase production by about 500% if properly executed. • On the right side, barren soil where grass is difficult to grow. • But on the left side, thanks to stony line and Zai system, sorghum crop is growing fairly well.
South East South
Tomatoes • In Brazil drip irrigation saves water and increasesyields. • Combined with minimum tillage it reduces soil erosion • It helps reduce the amount of fungal infection and so the use of chemicals • It ensures nutrients are directed accurately at the roots of each plant and so reduced the use per area. Do you know about minimum tillage? Why would that reduce soil erosion? Why would it reduce fungal infection? Fertilizer application?
It is not just any water .. • 1.1 billion people (1/6 of world population) do not have access to clean drinking water. • This know as potable water. • Obviously if you live in an area of water surplus, your chances are having access to sufficient potable water is better than if you are in an area of water deficit. • But that is not the whole story. • But other things figure in this as well – • location (rural/urban), • wealth (HIC/LIC). • How do you think this affect whether you have clean water or not? • Access to sanitation is important to ensure safe drinking water – If you do not adequate sanitation, what is likely to happen to the drinking water?
Is there anywhere, where there is lots of water available but not enough of it is potable? Or where there is not much water but most people have access to potable water How much water is available?
Its also about governments • Where a country relies on a major river, if the river passes through other countries first it is likely that there may be ‘water wars’ in the future. • For example the River Nile – what countries does this river pass through?
Résumé • What % of the water in the world is fresh (as against salty)? • What fraction of the population do not have access to fresh water? • What is potable water? • Can you think of some countries that have less than 65% of their people having access to it?
Extension homework • Did you know that the average person in the UK uses 150 litres per day (in their home)? • The government have set a target to reduce it to an average of 120 litres per person per day • This does not include the water used to grow the food that you eat or the products you buy • So if you have a water meter – read the meter and then leave it for 24 hours or 48 hours is better. • The difference will be in cu metres so X 1000 to turn into litres, then divide by the number of people in the house, and if you did it for more than 1 day, divide by the number of days to find out your personal average. Is it better or worse that the average/target?
Here are some of the uses of waterAgriculture What is going on here? Do you know what this called? What is going on here?
India is similar to other low/middle income countries • Why do you think India still uses so much water in agriculture? • As India becomes more industrialized, industries needs will rise • What industries use most of the water at the moment?
Industrial use in India And as India industrializes more More water will be needed
Indian Industry What is the main thing that is burnt to make electricity> • Thermal power • that is it burns things – • engineering • textiles • paper • All use a lot of water and soon more will be needed • According to the World Bank, the water demand for industrial uses and energy production will grow at a rate of 4.2 per cent per year, rising from 67 billion cubic meter in 1999 to 228 billion cubic meter by 2025. Why is so much water needed?
Not only industry will need more • What are 2 issues shown here that say that India will need more water in future?
So we have a neat little case study here • Example of growing water usage in a country • Place: India • How do they use their water at present? • Domestic: ? Industrial:? Agriculture:? • Why will it rise? • Industrial use: ? • (think – which industries use most? Which will increase? By how much will it increase?) • Domestic use?: • (Population: what is happening to it – figures. Potable water – mention that have done well but still need?)
Ways to improve things • In rural areas, dig wells which you then line and cover to prevent them becoming contaminated. • On a large scale, build dams to collect water that can then be distributed to irrigate agricultural land and take fresh water to the cities • On a smaller scale, build infrastructure ( long word for pipes and taps) in the poorer parts of cities. • Waste less!