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Syllabus
September, 2006 iii
Land and Water Development
Introduction to the Specialisation Land and Water Development. Availability of land and
water resources on a global and regional scale to meet the present and future food
requirements. Need for land and water development in rural and urban areas. Principles of
land and water development. Economic and social incentives and history. Physical planning
and environmental impact aspects. Various aspects of water management.
5 periods
Oral discussion
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Contents
September, 2006 v
CONTENTS Page
1 INTRODUCTION 1.1
1.1 Scope of the subject and definitions 1.1
1.2 These lecture notes 1.2
1.3 References 1.2
2 NEED FOR LAND AND WATER DEVELOPMENT 2.1
2.1 Need for land and water development for agriculture in view of 2.2
population growth and sustainable rural development
2.1.1 Food supply on a global scale: past, present and outlook 2.7
to the future
2.1.2 Factors that determine crop yield 2.21
2.2 Need for land and water development for urban and industrial growth 2.23
2.3 Crucial questions 2.24
2.4 References 2.27
3 PRESENT AND FUTURE AVAILABILITY OF LAND AND 3.1
WATER RESOURCES
3.1 Land resources 3.1
3.2 Water resources 3.3
3.3 References 3.10
4 CONCEPTS OF LAND AND WATER DEVELOPMENT 4.1
4.1 Development approach 4.1
4.2 Development strategies 4.1
4.3 Development stages 4.7
4.4 Socio-economic requirements 4.11
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Contents
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Page
4.5 Environmental considerations 4.134.6 References 4.14
5 PHYSICAL PLANNING IN RURAL AND URBAN AREAS 5.1
5.1 Area and time scales 5.1
5.2 Future changes and developments 5.7
5.3 References 5.8
6 WATER MANAGEMENT IN RURAL AND URBAN AREAS 6.1
6.1 Water management 6.1
6.1.1 Factors influencing the design of water management systems 6.1
6.1.2 Flood management and flood protection 6.6
6.2 Irrigation 6.9
6.2.1 Irrigation in sloping areas 6.16
6.2.2 Irrigation in level areas 6.17
6.3 Drainage 6.19
6.3.1 Drainage in sloping areas 6.33
6.3.2 Drainage in level areas 6.34
6.4 Combined and separate irrigation and drainage systems 6.38
6.5 Basic components in urban drainage systems 6.40
6.5.1 Role of water in an urban environment 6.41
6.5.2 Review of urban water management systems 6.41
6.5.3 Properties of and requirements regarding urban water 6.44
management systems
6.6 References 6.48
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Introduction
September, 2006 1.1
The pace of change in our world is speeding up, accelerating to the
point where it threatens to overwhelm the management capacity ofpolitical leaders. This acceleration in history comes not only from
advancing technology, but also from unprecedented world
population growth, even faster economic growth, and the
increasingly frequent collisions between expanding human
demands and the limits of the earth's natural systems.
Lester R. Brown, 1996
1 INTRODUCTION
1.1 SCOPE OF THE SUBJECT AND DEFINITIONS
These lecture notes are dealing with the utilisation of natural and man made land areas and the
physical measures to make these suitable or improve the conditions for various land uses,
like:
agriculture (area of special attention);
urban and industry;
nature reserves;
recreation areas.
Land and water developmentis the technology of adapting and managing land and water
resources for specific forms of land use in rural, urban and industrial areas.
Land reclamation is dealing with the technical methods and institutional aspects of land
utilisation, given the specific conditions and potential land use of a particular natural area.
Land consolidation is dealing with the technical and institutional aspects to modify rural areas
in order to improve the land use conditions rationalise agricultural production.
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Introduction
September, 2006 1.2
1.2 THESE LECTURE NOTES
These lecture notes start with a description of the need for land and water development,
primarily for agriculture in view of population growth and sustainable rural development. The
various aspects of food supply on a global scale in the past, at present and in future will be
reviewed. This will be followed by a description of the need for land and water development
related to urban and industrial development. In chapter 3 a brief review will be given of the
present and future availability of land and water resources. In chapter 4 the various concepts
of land and water development will be reviewed, including socio-economic requirements and
environmental considerations. In addition a review will be given of physical planning aspects
in rural and urban areas. Finally the water management issues in rural and urban areas will be
reviewed, including the various aspects of irrigation, drainage and flood management, with
their interactions.
The lecture notes cover primarily hydraulic and hydrological engineering aspects of land
utilisation. Also involved are: structural engineering, soil science, agronomy, economy,
sociology, and environmental aspects and impacts.
1.3 REFERENCES
Brown, L.R., et al., 1996, State of the World 1996, The Worldwatch Institute, Earthscan
Publications Ltd., London, United Kingdom.
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2 NEED FOR LAND AND WATER DEVELOPMENT
Developments depend on the physical conditions at any given place.
Looking at the situation in various countries, several developments
can be distinguished, which sooner or later will ask for intensive
attention. Why certain developments occur depends on the needs of
society, how they occur can be seen as the result of the interaction of
the will to develop, vision on desired developments, available means
(capital, labour, materials), technology and management
Van Dis, 1993
In analysing the need for land and water development, for the rural areas distinction should be
made between the need caused by the increase in population and in the consumption per
person, compensation for the loss of agricultural land, and the reduction in existing yield
levels. For the urban and industrial areas, the need is caused by the rapid development of such
areas all over the world (Schultz, 1993).
There is a great need for land and water development, aiming at the improvement of living
and production conditions in the rural areas, land reclamation, and the development of urban
and industrial areas with related facilities. The projects will have to be developed and
implemented in such a way that on the one hand the objectives are realised, and on the other
hand the environmental impacts are at an acceptable level. The projects may strongly differ in
type and scale. Answers to the following crucial questions determine the living conditions of
the users for many decades:
what will be the need for development;
which level of service will be required;
what will be the role of the government;
what will be the side effects of the development.
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Through the history land and water development has gone through different stages. In a wet
country like the Netherlands, for example, first water management activities aimed at
reclaiming lowlands by simple small-scale drainage systems. Due to the resulting subsidenceproviding safety against floods followed this. This was initially realised by making artificial
mounds and in a later stage by building dikes (Van de Ven, 2004 and De Bruin and Schultz,
2003). Then came the stage of agricultural water management, which implied the discharge of
excess water during winter. Later it also included the provision of irrigation water for the
higher areas. In the twentieth century, the Dutch ran into a wide variety of water quality
problems, which drew much attention in the seventieth and eightieth. In the ninetieth,
attention was drawn to a wider concept of water management, called integrated water
management. In this concept, account is taken of all functions waters fulfil, including those
of nature and environment, so that these functions can be secured on the long term. In the
beginning of the twenty-first century we are still in this phase. However, in studies for future
development even the approach is based on integrated environment management.
2.1 NEED FOR LAND AND WATER DEVELOPMENT FOR AGRICULTURE IN
VIEW OF POPULATION GROWTH AND SUSTAINABLE RURAL
DEVELOPMENT
Initially man used to live from collecting, hunting and fishing. By this way of living the
density at which the system would be in balance amounted less than 1 person/km 2. Some
10,000 years ago man started with the domestication of animals and cultivation of land (most
probably in the Middle East, or China, or simultaneously). Shifting cultivation allowed for an
increase in density to 3 persons/km2.
In the period prior to the Industrial Revolution (1650 - 1750) the average population growth
amounted to only some 0.3% annually. The rate of growth of the worlds population showed a
sharp increase in the seventeenth and eighteenth century. This increase was closely related to
the Agricultural Revolution and the Industrial Revolution. The Agricultural Revolution
resulted in a change in the way of living. Before the Industrial Revolution biological energy
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converters controlled the supply of energy. With the Industrial Revolution fossil energy
became available to cultivate land, breed animals and to produce fertilisers. After the
Industrial Revolution the population growth raised to 3% annually. The following causes forthis explosive growth may be mentioned:
the invention of the steam engine by Watt in 1752, which can be considered as the start of
the Industrial Revolution;
the introduction of fertilisers in the nineteenth century increased crop yields tremendously,
for example for cereals from less than 1,000 kg/ha to more than 8,000 kg/ha at present;
many diseases, such as cholera, pest and small pox, common in the Middle Ages and
decimating entire populations, became controlled, or even extinguished. This also applied
to agricultural crops;
large regions in the world with a low population density, such as North America and
Australia became immigration areas. For example in the period 1846 - 1930 some 50
million people immigrated to new areas, where they introduced the new techniques of the
Industrial Revolution.
In 1804 there were 1 billion people. 2 billion was reached in 1927. By December 2005, there
were 6.5 billion people of which almost 80% lived in the developing world with an average
growth rate of 2.2%. The others inhabited the industrialised countries, with a growth rate of
0.6%. Projections for the year 2025 show an increase in population up to 8 billion people,
from which the major part is expected to take place in developing countries (Figure 2.1) (UN
Population Bureau, 2005).
The population and its growth for the least developed countries, the emerging countries and
the developed countries are given in Figure 2.2. In this figure the three categories of countries
have been identified based on the Gross National Income per capita (GNI) and the
classification as given by UNCTAD (The World Bank, 2003 and UNCTAD, 2002). GNI
being defined as the Gross Domestic Product (GDP) plus net receipts of primary income
(compensation of employees and property income) from abroad, divided by the midyear
population. The UNCTAD classification is based on factors, viz.: low national income (per
capita GDP under US$ 340), weak human assets (a composite index based on health, nutrition
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and education indicators) and high economic vulnerability (a composite index based on
indicators of instability of agricultural production and exports, inadequate diversification and
economic smallness). Based on these considerations the categories are: developed countries (GNI > ~US$ 14,000). Most of the countries in Western and Central
Europe, North America, the larger countries in Oceania and some countries in Asia;
emerging countries (a higher standard of living than the least developed countries as
identified by UNCTAD and a GNI < ~US$ 14,000). Most of the Eastern European
countries (including Russia), most of the countries in Central and South America, most of
the countries in Asia (including China, India and Indonesia), and several countries in
Africa;
least developed countries (based on the UNCTAD classification). Most of the countries in
Africa, several countries in Asia, 1 country in Central America and most of the smaller
countries in Oceania.
0
1
2
3
4
5
67
8
9
10
1950 1970 1990 2010 2030 2050
Figure 2.1 Growth of the world population since 1950 and medium projection up to 2050
(UN Population Bureau, 2005)
Population density is generally expressed compared to the total area of a country. If we look,
however, at the population density with reference to the arable land then the result per
Continent is shown in Table 2.1 (International Commission on Irrigation and Drainage, 2004
and Schultz, et al., 2005). From Table 2.1 it can be easily observed that the Asian continent
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has by far the largest population and the highest population density, both with reference to the
total area, as well as to the arable land. If we also take into account the population growth as
shown in Figures 2.1 and 2.2, than it will become clear that in the coming decades most of theactivities with respect to water management and flood protection may be expected in Asia. If
we have a closer look on a country basis than Table 2.2 shows the five most densely
populated and the five least densely populated countries with respect to the arable land.
0
2
4
6
8
10
Million
2005 2025 2050
Year
Least DevelopedCountries
Emerging Countries
Developed Countries
Figure 2.2 World population and growth in least developed countries, emerging countries
and developed countries (Schultz, et al., 2005)
The world economy is growing even faster than the population. It has expanded from US$ 4
trillion in output in 1950 to more than US$ 20 trillion in 1995 (Brown, 1996). Due to this
development the standard of living in many countries is rising rapidly. This results amongothers in an increase in consumption and a change in diet per person. This is an extra
contribution to the required increase in food production, which, together with the increase in
population results in the expectation that duplication in food production will have to be
achieved in the coming 25 years (Van Hofwegen and Svendsen, 2000).
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Table 2.1 Continents and types of countries ranked according to population density with
reference to arable land (International Commission on Irrigation and Drainage,2006 and Schultz, et al., 2005).
Continent Total area
in 106 ha
Arable land
in 106 ha
Total
population
in million
Population density
in persons/km2
with reference to
total area Arable
land
Asia
Africa
Europe
America
Oceania
3,177
3,032
2,299
3,997
806
558
213
297
390
53
3,911
906
729
892
33
123
30
32
22
4
701
425
245
229
63
World 13,311 1,511 6,471 49 428
Developed countries
Emerging countries
Least developed countries
3,186
8,046
2,079
375
996
140
961
4,751
759
30
59
37
256
477
541
2.1.1 Food supply on a global scale: past, present and outlook to the future
Food requirement
Agriculture has the objective to supply man with energy. The daily food requirement per
person is 10,000 kJ energy from carbohydrates (sugar) and fat and 70 g protein (including
minerals and vitamin).
In case of a vegetarian Table 2.3 gives the amount of cereals, pulses and vegetables that are
required to meet the daily energy and protein requirement. In the same table the area of land
needed to feed one vegetarian is indicated, given the average production rates in the world. So
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for one vegetarian about 1,600 m2 of agricultural land is needed. In other words, with present
average production rates 6 vegetarians can be fed from one hectare of agricultural land.
Presently 6 billion people have their food from 1.6 billion ha of agricultural land, whichmeans that on average less than 3 persons are fed from one hectare. The difference is, among
others, caused by the fact that most people eat meat to get protein. The production of energy
through meat is very inefficient. It requires ten times as much land to produce the same
amount of energy in the form of meat.
Table 2.2 Some characteristic data for the five most densely and five least densely populated
countries with reference to the arable land (International Commission on
Irrigation and Drainage, 2006 and Schultz, et al., 2005).
Country/
geographic unit
Total area
in 106 ha
Arable
land
in 106 ha
Total
population
in million
Population density
in persons/km2
with reference to
Economic
status *)
total area arable land
Five most densely populated
Chinese Taipei
Japan
South Korea
Egypt
Bangladesh
4
38
10
100
14
0.7
4.8
1.9
3.4
8.5
23
128
48
74
142
596
339
481
70
985
3,243
2,691
2,543
2,074
1672
D
D
D
E
L
Five least densely populated
Australia
Congo, Republic
Kazakhstan
Canada
Russia
774
34
273
997
1,708
49
8
22
46
126
20
7
15
32
143
3
12
5
3
8
42
51
68
70
114
D
L
E
D
E
*) D = Developed country E = Emerging country L = Least developed country
Regarding the actual food consumption there is a striking difference between developing and
developed countries. Per capita consumption in the least developed countries averages 180 kg
of grain per year. The same consumption in the developed countries amounts to a figure of
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1,000 kg (World Resources Institute, 1992).
Table 2.3 Area required to feed one vegetarian for one year for assumed average worldproduction rates
Food Amount per person
in gram/day
Average yield
in kg/ha
Required area
per person in m2
Cereals 600 1,800 1,200
Pulses 100 1,000 360
Vegetables 250 23,000 40
The best indicator for the food situation is the number of calories per capita and per day as
given in Table 2.4. The figures differ widely from one region to another. The absolute
minimum is 1,600 to 1,700 calories. Sub-Saharan Africa is only little above it. In spite of the
target set by the FAO at the first World Food Conference in 1974 to abandon hunger within
ten years world-wide, 800 million people in 88 countries suffer from acute lack of sufficient
food. Half of these countries are situated in Africa, 23 in Asia, 12 in Eastern Europe and 9 in
Latin America. Moreover, 2 billion people suffer from permanent under nourishment, which
situation may already occur for many generations. The under nourishment is caused by too
little variation in the total food package.
Cereals form the most important part of the food. Table 2.4 gives yields in kg/ha, which are
highest in Western Europe and North America and very low in Africa. There are various
reasons for this fact, one being the prevailingly low quality of the African soils.
Relation between crop yield and population growth
Until 1950 there was a close relation between crop production and size of the population. The
growth in agricultural area was more or less equal to the growth in population. If there was
not enough food, the agricultural area extended. The yield per ha remained until the beginning
of this century more or less constant. For realising the increase in yield the best soils were
selected. Thus, during calamities there was no buffer and the extent of the population
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declined, which was rather common in Europe, even in the middle of the nineteenth century.
An example is Ireland, where the population decreased from 8.5 million around the middle of
the nineteenth century to 4.5 million at present.
Table 2.4 Production of food and cereals in 1990 in different regions
Area Population
in million
Food consumption Cereals
cal/
cap.-day
Yield
in kg/ha
Availability
in
kg/cap.-year
Cropland/
capita
in ha
World 5,293 2,700 2,600 340 0.28
Western Europe 498 3,400 5,000 590 0.28
Eastern Europe - 4,000
Russia 288 - 1,800 680 0.81
Asia 3,109 2,400 2,600 250 0.15
North and Central
America
427 3,650 3,600 800 0.65
South America 297 2,700 2,040 270 0.49Africa 648 1,150 130 0.30
Sub-Saharan Africa - 2,100 - - -
Figure 2.3 shows that between 1950 and 2000 the agricultural area has increased by 21% and
the population growth was 123%. This would have meant starvation if the production per ha
was not increased. Figure 2.4 shows the growth in world grain production. In the period 1950
- 2000 the grain production increased by 2.6 times the production of 1950. This could be the
case because of better varieties, tillage practices, and water management. The increase in the
production per ha realised up to now can be summarised as follows:
1950 - 1960 26%
1960 - 1970 21%
1970 1980 20%
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Figure 2.3 Development of world grain land
Figure 2.4 Development of world grain production
0
2
4
6
8
10
12
14
16
18
20
1950 1960 1970 1980 1990 2000
Year
106
ton
0
100
200
300
400
500
600
700
800
900
1 000
k
World rain roduction in 106ton
Per ca ita rain roduction in k
0
100
200
300
400
500
600
700
800
1950 1960 1970 1980 1990 2000
Year
106
ha
0.00
0.10
0.20
0.30
ha
Total rain land in 106 haPer capita grain land in ha
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The increase in production with time is an S-shaped curve with a certain limit. In other words,
the increase in agricultural production is slowing down. Unfortunately, the increase in
slowing down of the population growth is at a much lower level than for agriculture.Although the population increase during the second half of the twentieth century is
substantially higher than the increase in agricultural area the grain production per person is
not much affected due to the increase in production per ha.
Required increase in worlds food production
The growth in population and worlds economy results in a tremendous growth in the demand
for natural resources. Since 1950 the need for grain and for the principal rangeland products -
beef and mutton - has tripled, consumption of seafood has increased more than four times and
water use has tripled. The increase in human demands for resources is beginning to outgrow
the capacity of earths natural systems. As this happens, the global economy is damaging the
foundation on which it rests. Evidence of the damage to the earths ecological infrastructure
takes the form of collapsing fisheries, falling water tables, shrinking forests, eroding soils,
dying lakes, crop-withering heat waves, and disappearing species (Brown, 1996).
Worlds food production, although steadily growing, fluctuates widely because of adverse
weather conditions, or natural disasters. The neck and neck race between food demand and
food production is presently in balance in most of the countries, while in the industrialised
countries food surpluses are found. Present problems with food shortage are mainly related to
matters of distribution and regional imbalance. During the last decades, the required global
increase in agricultural production has been realised, amongst others by the introduction of
High Yielding Varieties of rice (HYV) and the improvement of water management systems.
In this period, China, Indonesia and India, with a total of more than 2 billion inhabitants,
became self-sufficient in rice.
Urbanisation and industrialisation, erosion, desertification, waterlogging, salinization,
environmental considerations, or degeneration of existing irrigation and drainage systems are
the causes of loss of agricultural land and reduction in agricultural yields (Schultz, 1993). On
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a global scale not less than 2 billion ha are subject to deterioration. Degeneration in an
extreme and irreparable form has occurred on 9.5 million ha (5.2 million in Africa).
Urbanisation and industrialisation result in a loss of about 13 million ha cultivated landannually. In arid and semi-arid regions, the introduction of irrigation has gradually resulted in
waterlogging and/or salinization problems, so that approximately 1.5 million ha have to be
taken out of production annually. In addition, most agricultural production in the world uses
farming practices that are environmentally unsustainable. Efforts are ongoing in the
industrialised countries to encourage more sustainable practices. Environmental sound
agriculture may result in more extensive agricultural practices, or may demand for highly
advanced irrigation and drainage systems with water treatment and recycling. These
developments make it doubtful whether agricultural exploitation will remain feasible under
these conditions. Degeneration of existing irrigation and drainage systems, due to lack of
attention to operation and maintenance, is a worldwide phenomenon.
In the sixtieth half of the total growth rate in food production came from newly reclaimed
areas. This dropped to one third in the seventieth and still more in the eightieth. The rate of
reclaiming new lands was 1% per year in the fiftieth but not more than 0.2% per year in 1990.
The spectacular increase of food production in the period 1960 - 1990 was mainly due to the
expansion of irrigation, which secured 70% of the production growth in the period 1961 -
1980, the proportion for Asia being even higher.
In order to get an impression of the distribution of the present agricultural production and the
net realised export surplus, data over the period 1999 - 2004 with respect to cereals have been
collected (FAO, 1999 - 2004). Under cereals the following crops are covered: rice, wheat,
maize, sorghum and millets. Because rice is a very important crop in most of the emerging
and least developed countries separate tables are shown for rice. The data for the continents as
well as for the categories of countries are shown in the Tables 2.5 to 2.8. Table 2.5 and 2.6
show respectively the cereal and rice production in million tonnes. In the Tables 2.7 and 2.8
the net trade (export) surplus of cereals and rice is shown in million tonnes, as well as in
percentage of the own production.
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Table 2.5 World cereal production in million tonnes for the period 1999 - 2004
(FAO, 1999 - 2004)1999 2000 2001 2002 2003*) 2004**)
Asia
Africa
Americas
Europe
Oceania
1,031
112
525
385
36
996
113
531
386
35
1,001
118
518
429
40
982
115
475
434
20
997
132
559
356
39
1,024
127
554
419
36
World 2,088 2,060 2,106 2,025 2,083 2,160
Developed countries
Emerging countries
Least developed countries
857
1,118
114
862
1,081
118
887
1,099
119
843
1,070
112
846
1,105
132
906
1,124
130
Global stock in million
tonnes
611 630 599 571 475 398
*) estimated **) forecasted
Interesting in Table 2.5 and 2.6 is that we see more or less a stable production over the past
six years in the continents, as well as in the type of countries. While in the same period the
population has grown, this implies that the global stock will have decreased. Table 2.5 and 2.6
show indeed a gradual decrease in the global stock, both for cereals and for rice.
From the Tables 2.7 and 2.8 it can be derived that the developed countries have a net trade
surplus, although it is only about 12% and 1.5% of their own production for respectively
cereals and rice. The emerging countries have a modest trade deficit of about 5% and 1.5% of
their own production for respectively cereals and rice. The least developed countries,
however, have the major trade deficit of about 38% and 12% of their own production for
respectively cereals and rice. Some characteristic average data on the cereal production are
shown in Figure 2.5 and on the rice production in Figure 2.6.
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Table 2.6 World rice production in million tonnes for the period 1999 2004
(FAO, 1999 - 2004)1999 2000 2001 2002 2003*) 2004**)
Asia
Africa
Americas
Europe
Oceania
555
17
34
3
1
545
18
32
2
1
545
17
32
3
2
517
18
32
3
1
538
18
31
3
0
556
18
35
3
1
World 610 599 599 572 592 613
Developed countries
Emerging countries
Least developed countries
26
533
51
25
519
55
26
519
53
26
491
55
23
511
57
25
530
58
Global stock in million tonnes 136 150 148 141 116 103
*) estimated **) forecasted
Figure 2.5 clearly shows that the largest cereal production is taking place in Asia, which takes
the major share of the cereal production in the emerging countries. However, the production
in kg/inhabitant is by far the largest in the developed countries. From Figure 2.6 it can be
easily derived that by far most of the rice production takes place in Asia. The net export
surplus is in all cases marginal.
The critical issue with which the world is confronted today is the problem of how to double
the global food production in the next 25 years and to triple it with says 50 years (double
population and more food per person, especially in Asia and Africa) (Van Hofwegen and
Svendsen, 2000). It is unclear whether these production increases indeed can be achieved.
Some factors foresee well for global production - for example, improvements in the emerging
market economies of Central Europe and agreements to liberalise agricultural trade. In the
longer term, improvements in for example Russias farm economy are certainly possible.
Better control of diseases (human and farm animal) could also open up large areas of
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potentially productive farming and grazing land in Africa.
Table 2.7 Net cereal trade surplus in million tonnes (T), or in % of own production (OP)1999/00 2000/01 2001/02 2002/03 2003/04* Average
T OP T OP T OP T OP T OP T OP
Asia
Africa
Americas
Europe
Oceania
-81.1
-40.7
82.4
18.7
20.7
-7.9
-36.5
15.7
4.9
57.7
-74.0
-43.5
82.1
12.5
20.6
-7.4
-38.7
15.5
3.2
58.4
-76.8
-44.8
80.7
17.9
21.0
-7.7
-38.0
15.6
4.2
52.6
-54.7
-50.2
59.6
34.6
13.4
-5.6
-43.6
12.6
8.0
67.7
-60.0
-43.1
93.8
-6.7
18.0
-6.0
-32.8
16.8
-1.9
46.2
-69.3
-44.5
79.7
15.4
18.7
-7
-38
15
4
56
Developed countries
Emerging countries
Least developed
countries
116.9
-74.5
-41.5
13.6
-6.7
-36.4
103.5
-62.4
-43.5
12.0
-5.8
-37.0
106.4
-62.8
-45.4
12.0
-5.7
-38.2
98.2
-41.9
-53.5
11.7
-3.9
-47.6
91.7
-43.8
-45.8
10.8
-4.0
-34.6
103.3
-57.1
-45.9
12
-5
-39
*) estimated
Table 2.8 Net rice trade surplus in million tonnes (T), or in % of own production (OP)1999/00 2000/01 2001/02 2002/03 2003/04* Average
T OP T OP T OP T OP T OP T OP
Asia
Africa
Americas
Europe
Oceania
5.4
-5.2
0.9
-1.6
0.3
1.0
-29.7
2.7
-51.6
21.4
5.8
-5.8
1.2
-1.3
0.1
1.1
-33.0
3.7
-40.6
9.1
7.1
-6.6
0.4
-1.4
0.2
1.3
-38.2
1.3
-43.8
11.1
8.2
-8.0
1.2
-1.5
0.1
1.6
-44.9
3.7
-46.9
7.7
8.3
-7.7
0.0
-1.5
-0.2
1.5
-42.5
0.0
-46.9
-50.0
7.0
-6.6
0.7
-1.5
0.1
1
-38
2
-46
0
Developed countries
Emerging countries
Least developed
countries
0.3
6.3
-6.6
1.2
1.2
-12.9
0.5
5.5
-6.0
2.0
1.1
-10.9
0.2
6.1
-6.3
0.8
1.2
-11.8
0.1
7.8
-7.9
0.4
1.6
-14.4
0.6
6.9
-7.5
2.6
1.4
-13.1
0.3
6.5
-6.9
1
1
-13
*) estimated
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-200
0
200
400
600
800
1000
1200
Asia
Africa
Europe
Americas
Oceania
D
evelopedcountries
E
mergingcountries
Leastdeveloped
countries
Pr. in million ton
Pr. in kg/inhabitant
NTS in million ton
NTS in kg/inhabitant
Pr. = production NTS = net trade surplus
Figure 2.5. Some characteristic average data on the situation with respect to cereal production
-100
0
100
200
300
400
500
600
Asia
Africa
Europe
Americas
Oceania
De
velopedcountries
E
mergingcountries
Leastde
velopedcountries
Pr. in million ton
Pr. in kg/inhabitant
NTS in million ton
NTS in kg/inhabitant
Pr. = production NTS = net trade surplus
Figure 2.6. Some characteristic average data on the situation with respect to rice production
At first sight and considering the world as a whole the problem to achieve the required
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increase in food production does not look insurmountable. The objective would be realised
within an average annual growth of 2.4%. There do not seem to be reasons why such a
percentage could not be maintained in future. Two favourable factors can be observed:increase of yield and reserve of agricultural land. With respect to the yields there is no
biological reason why the global average of cereals in the year 1990 (2,600 kg/ha) could not
be doubled. Besides the cropland area of 1990 (1,500 million ha) there is a reserve of 2,000
million ha of potential agricultural land of which some 600 million ha consist of lowland. In
some areas (for instance the delta of the Mekong river in Vietnam) spectacular results have
been booked with the introduction of 100-days rice varieties enabling to raise two crops per
year avoiding critical periods of deep flooding or low flow and intrusion of sea water.
This optimistic picture is offset by a number of negative factors. First of all there is the
slowing down of the reclamation of new agricultural land. This is due to the fact that the best
areas have already been reclaimed. In Asia, for instance, it is estimated that 82% of the
potential agricultural land area is already under production. There are still large reserves of
potential agricultural land in America and Sub-Saharan Africa but for much of these reserves
the soil is marginal, being suitable only for perennial tree crops, or rainfall is unreliable.
There is much ecological opposition against conversion of the tropical rain forests (Amazon,
Yunnan forests in China, Thailand, and Myanmar) into agricultural lands. The lowlands,
which have a high potential, comprise the wetlands (swamps and marshes, lakes, lagoons, or
lower flood plains), which also form a valuable ecological asset. In recent years development
of irrigation slowed down accordingly. Whereas between 1950 and 1980 the irrigated area
increased with about 4 million ha per year, in 1990 it was only about 2 million. This reduction
of irrigation investments is the result of the fall of product prices and disappointing low yields
after the implementation of new projects. The frontiers of land resources are attained in
countries with large irrigation systems. Either the available land resources are fully developed
(Pakistan, Egypt, Japan, the Netherlands) or the costs of future expansion are becoming too
high (India, China). In developing countries there remains an unused potential of over 100
million ha of irrigable land but a substantial part of it lies outside the regions of greatest need.
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Relation water management and agricultural production
With respect to water management related to agricultural production there are broadly
speaking three agro-climatologic zones, being: temperate humid zone, arid and semi-arid
zone and humid tropical zone. In addition, in principle, four types of cultivation practices may
be distinguished, being:
rainfed cultivation, without or with a drainage system;
irrigated cultivation, without or with a drainage system.
Dependent on the local conditions different types of water management with different levels
of service will be appropriate (Schultz, 1993). In the temperate humid zone agriculture
generally takes place without a water management system, or with a drainage system only.
Supplementary irrigation may be applied as well. In the arid and semi arid zone agriculture is
normally impossible without an irrigation system. Drainage systems may be applied as well
for salinity control and the prevention of waterlogging. In the humid tropical zone generally a
distinction is made in cultivation during the wet and the dry monsoon. During the wet
monsoon cultivation is generally possible with a drainage system only, although quite often
irrigation is applied as well to overcome dry spells. In the dry monsoon irrigation is generally
required to enable a good yield.
The total cultivated area on earth is about 1.5 billion ha, which is 12% of the total land area.
At about 1.1 billion ha agricultural exploitation takes place without a water management
system (Table 2.9). Presently irrigation covers 270 million ha, i.e. 18% of worlds arable land.
Irrigation is responsible for 40% of crop output and employs about 30% of population spread
over rural areas. It uses about 70% of waters withdrawn from global river systems. About
60% of such waters are used consumptively, the rest returning to the river systems. Drainage
of rainfed crops covers about 130 million ha, i.e. 9% of worlds arable land. In about 60
million ha of the irrigated lands there is a drainage system as well. From the 130 million ha
rainfed drained land it is roughly estimated that about 15% crop output is obtained. No figures
are available of the employment of the population in these areas, but it is supposed to be about
10%, which is relatively smaller than for the irrigated areas, while a significant part of these
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areas is located in the developed countries with relatively large farm sizes.
Table 2.9 Role of water management in agricultural cultivation practices in the differentcontinents (International Commission on Irrigation and Drainage, 2006 and
Schultz, et al., 2005).
Continent Total
area
in 106 ha
Arable land
in 106 ha
Total
population
in million
Water management practice
in % of the arable land
No
system
Drainage
*)
Irrigation
**)
Asia
Africa
Europe
Americas
Oceania
3,177
3,032
2,299
3,997
806
558
213
297
390
53
3,911
906
729
892
33
56
92
74
73
90
10
2
18
17
4
34
6
8
11
5
World 13,311 1,511 6,471 70 12 18
Developed countries
Emerging countries
Least developed
countries
3,186
8,046
2,079
375
996
140
961
4,751
759
64
70
86
25
8
3
12
22
11
*) In total about 130 * 106 ha rainfed and 60 * 106 ha drainage of irrigated areas
**) Irrigation may include drainage as well
The present situation and in particular the present development trends make it plausible that
future expansion of the production will mainly be achieved by increase in yields and by
cropping intensification. Reclamation of new land will be limited to special areas, which by
virtue of location and quality are most promising for growing special crops (vegetables and
fruits) and for urban and industrial expansion. The increase in agricultural yields can be
realised through improved agricultural practices, water management, transport and marketing
facilities. Studies into the world food supply in the coming decades underline that about 90%
of the extra food should come from the present 1,500 million ha cropland of the world (World
Resources Institute, 1992 and Van Hofwegen and Svendsen, 2000). However, a certain
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amount of food about 10% - needs to be produced on new agricultural land. These new
lands can be reclaimed in upland and in lowland areas. For development of upland areas,
irrigation and sometimes also drainage will be required, whereas for development oflowlands, drainage and in most cases also irrigation will be needed.
Form Table 2.9 it can be seen that still the largest agricultural area is without any water
management system. In the rainfed areas without a water management system water
harvesting, and watershed management can make some improvements. Such measures may
undoubtedly help to improve the livelihood of poor farm families. There is, however, no way
that the cultivated area without a water management system can contribute significantly to the
required increase in food production. Due to this the share of irrigated and drained areas in
food production will have to increase. This can be either achieved by installing irrigation, or
drainage systems in the areas without a system, improvement, or modernisation of existing
irrigation and drainage systems, installation of irrigation systems in the rainfed drained areas,
or installation of drainage systems in irrigated areas. My personal estimate is that over the
next 25 years this may result in a shift to the contribution to the total food production in the
direction of 30% for the areas without a water management system 50% for the areas with an
irrigation system and 20% for the rainfed areas with a drainage system. It has to be realised
that these percentages refer to two times the present day food production. In addition it has to
be realised that it will be extremely difficult to achieve this in an environmentally sustainable
way, especially in the emerging countries.
2.1.2 Factors that determine crop yield
Factors that determine the crop yield are:
soil conditions
In the past the type of soil was governing the possibilities and constraints for agriculture.
Soils used to be divided in poor and rich soils in order to distinguish between the
nutrient availability for the crops. The introduction of fertilisers made this distinction
redundant. Nowadays good and bad soils are distinguished, indicating the suitability of the
soil for crop production in relation to water management, and tillage practices. In other
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words the soil physical conditions which determine the management of the soil are
nowadays much more important than the chemical properties (nutrient supply). The
following aspects play an important role:* water
Deep-ploughing and organic matter can improve the moisture retention in the soil;
* air
Aeration of the root zone is of importance, as most plants get their oxygen via the
roots. Aeration can be improved by drainage and improvement of the soil structure;
* temperature
The optimum temperature for most crops is between 15 and 35 oC. Temperature is an
important reason for draining agricultural land in North-western Europe. By removing
water from the soil in spring, the soil is heated at a faster rate and the cultivation of
crops may start earlier;
* nutrient supply
During the last 40 years the use of fertilisers in the world has increased by a factor 10
from 14 to 145 million tons per year. It is expected that food production will decrease
by 40% if the supply of fertilisers is abruptly discontinued;
* root penetration
The soil is the food hold for crops. Where required a good root penetration can be
realised by measures like deep ploughing, subsoiling, drainage and fertilising;
* injurious factors
Injurious factors refer to soil toxicity, soil-born diseases and the like;
CO2 concentration
For the process of photosynthesis the plant uses water from the soil, taken up by the roots,
CO2 from the air, taken up through the leaves and energy from the sun to produce sugars
(and oxygen). The CO2 content in the air affects the photosynthesis process. In green
houses the CO2 content is artificially increased. However, the natural CO2 content in the
air of 0.03% cannot be influenced, although on a global scale it shows a tendency to rise
due to the world-wide use of fossil energy and deforestation;
radiation from the sun
Radiation varies with latitude and during the year. Moreover it is influenced by the
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weather (cloudiness). Radiation determines to a large extent the agricultural production
capacities. This can be illustrated by the fact that in tropical areas three to four crops per
year can be grown whereas in temperate zones this is usually one crop per year; control of pests and diseases
The introduction of monocultures necessitated the control of accompanying pests and
diseases. Next to mechanical and chemical control, nowadays biological control is more
and more applied, because of the limited unwanted side effects. Important is also the
breeding of varieties resistant to pests and diseases;
production efficiency
Some crops show a relatively high photosynthetic efficiency, for example sugar cane,
maize (corn), sorghum and millet. Other crops are less efficient. The difference between
efficiencies is highest at low latitudes (high temperature, high light intensity);
breeding of new varieties
Introduction of high yielding varieties with favourable characteristics, such as resistance
for lodging, quick leaf growth, and favourable grain/straw ratio;
tillage practices
Present low yields are often due to a lack of knowledge and capital to realise optimal
tillage practices.
Table 2.10 shows for a number of crops the theoretical maximum yield and the target yield,
which is to be obtained on a large scale.
2.2 NEED FOR LAND AND WATER DEVELOPMENT FOR URBAN AND
INDUSTRIAL GROWTH
Due to the rapid expansion of urban and industrial areas, the percentage of people living in
urban areas increased from 30% in 1950 to 43% in 1990 (United Nations, 2000). It is
expected that this development will continue to an estimated 61% in 2030 (Figure 2.7). The
major part of urbanisation is expected to take place in deltaic and coastal areas. This means
that lands have to be prepared for new urban and industrial areas. As the suitable locations
have already been developed, this will be increasingly difficult (Oudshoorn, et al., 1999).
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Table 2.10 Potential crop yields in different climatic zones
Temperate zone (one crop) Tropics (per year)theoretical
maximum
target yield in theoretical
maximum
target yield in
in ton/ha ton/ha 106 kJ in ton/ha ton/ha 106 kJ
Cereals
Wheat 12 9 130 25 18 259
Rice 12 9 93 30 20 207
Maize (corn) 15 11 167 38 24 364
Sorghum and millet 15 11 147 40 26 347
Root crops
Potato 100 65 173 140 80 213
Cassava - - - 100 65 345
Sweet potato and yam 80 50 197 160 100 396
Legume crops
Soybean 9 7 112 20 15 240
Ground nuts 12 9 153 30 20 339
Dry beans 8 6 85 18 12 169
2.3 CRUCIAL QUESTIONS
The above shows that there is a great need for land and water development, aiming at the
improvement of living and production conditions in the rural areas, land reclamation, and the
development of urban and industrial areas with related facilities. The projects will have to be
developed and implemented in such a way that on the one hand the objectives are realised,
and on the other hand the environmental impacts are at an acceptable level. The projects may
strongly differ in type and scale. Answers to the following crucial questions determine the
living conditions of the users for many decades:
what will be the need for development;
which level of service will be required;
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what will be the role of the government;
what will be the side effects of the development?
0
10
20
30
40
50
60
70
80
90
Percentage
World Africa Asia LAC MDR
1950
1990
2030
LAC = Latin America and the Caribbean MDR = More Developed Regions
Figure 2.7 Percentage of urban population
Need for development
The need for development in rural areas is generally determined by the need to increase
and/or to rationalise food production and to promote sustainable rural development. In other
words, there is a direct link between the investments to be made and the benefits to be
expected. These benefits generally include the increase in yields, but may also be expressed in
a more efficient production by better transport facilities, an improved marketing system and
sustainable development. This direct link enables planners to identify which investments may
be justified. Land and water development projects for rural areas have been generally purely
agricultural development projects. Recently also other land uses, like recreation and nature
conservation, are integrated in the plans. From a technical point of view, the questions to be
solved refer to the water management system, the infrastructure, the drinking water supply
and sewerage, and required facilities. As all physical structures need to be maintained, all
these questions have to be taken into account from a design point of view, and from an
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operation and maintenance point of view.
Investments in urban areas are generally justified by the need for areas for living, industry,and/or commercial development. In this case government investments generally have to be
repaid by the sale of land, or through taxes. These projects are more complex than projects for
rural areas, as many more components have to be developed and integrated. Another essential
difference is that investments per square metre are much higher in urban areas than those
needed in rural areas. From a technical point of view the questions to be solved refer to the
preparation of building sites, foundation aspects, storage and removal of surplus rainwater,
water supply for the green areas, infrastructure, drinking water supply and sewerage, and
required facilities. The maintenance of public facilities is generally the responsibility of the
municipality, who will levy taxes to finance the maintenance.
Required level of service
The success of a project is strongly determined by the creation of an attractive environment
for the users to initiate and continue the proposed activities (Constandse, 1988). This means
that the project has to be attractive and implies that it can be maintained adequately. From the
development projects of the last decades it can be concluded that several land and water
development projects did not improve the living conditions of the users. In the case of
improved areas, this resulted in an unwillingness or incapability of the users to contribute to
the required recovery of investments and/or operation and maintenance. In the case of newly
developed areas, this simply meant that the settlers either tried to return to their previous
living areas, or moved elsewhere.
In the design of water management systems for rural areas, the determination of the required
level of service is a complicated matter, as the interaction between water management and
crop yield is difficult to quantify. Insight in the sustainability of such systems requires first of
all insight in the expected crop yield, farm practices and the capacity of the farmers to
contribute to the required maintenance activities. Based on such information and on the
meteorological, hydrological and soil conditions, water management systems can be designed.
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Where required, a legal framework and an organisational structure have to be developed to
realise the operation, maintenance and management.
In urban areas, investments in property are generally that high, those investments in the urban
water management system are easily justified. Here, however, the level of service also
concerns various recreational facilities, like parks and sports fields, to make living in the
urban area attractive.
Role of the government
In most land and water development projects the government plays an important role, as she
initiates developments that fit in her development policy, and by preventing unwanted
developments. Concerning the technical aspects, she is in charge for land use, or development
plans, the required legal framework, standards concerning the functioning of systems, and in
many cases for the actual implementation. It will be clear that the different levels in the
government will play different roles.
Side effects of development
Each development will result in side effects. In many cases these side effects caused a lot of
trouble (Volker, 1987). It is the responsibility of the organisation in charge of the
development, to identify possible side effects and to prevent the negative ones as much as
possible. This can be realised by adapted designs, and by establishing a legal framework and
control mechanism. Some typical side effects are impact on the existing (geo)hydrological
regime, damage to existing natural values, and pollution of air, soil and water. Especially this
last aspect resulted and still results in many problems, leading to substantial costs afterwards
for cleaning what was polluted. To prevent negative side effects as much as possible, many
countries demand an environmental impact analysis and appropriate measures.
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2.4 REFERENCES
Brown, L.R., et al., 1996, State of the World 1996, The Worldwatch Institute, Earthscan
Publications Ltd., London, United Kingdom.
Bruin, Dick de and Bart Schultz, 2003, A simple start with far reaching consequences.
Irrigation and Drainage 52.1.
Constandse, A.K., 1988, Planning and creation of an environment, IJsselmeerpolders
Development Authority, Lelystad, the Netherlands.
Dis, M.M.U. van, 1993, Key-factors, Water Management in the Next Century, Address
presented during the SOTA-symposium, Royal Institute of Engineers in the Netherlands,
Division of Water Management (in Dutch), the Hague, the Netherlands.
Hofwegen, P.J.M. van and M. Svendsen, 2000, A vision of water for food and rural
development, the Hague, the Netherlands.
International Commission on Irrigation and Drainage (ICID), 2006, Updated statistics on
irrigation and drainage in the world, www.icid.org, New Delhi, India.
Oudshoorn, H., Bart Schultz, A. van Urk, and P. Zijderveld, ed., 1999, Sustainable
development of deltas. Proceedings International conference at the occasion of 200 year
Directorate-General for Public Works and Water Management, Amsterdam, the Netherlands,
23 - 27 November, 1998, Delft University Press, Delft, the Netherlands.
Schultz, Bart, 1993, Land and water development. Finding a balance between
implementation, management and sustainability, Inaugural address, IHE, Delft
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Schultz, Bart, 2001, Irrigation, drainage and flood protection in a rapidly changing world,
Irrigation and Drainage, volume 50, no. 4.
Schultz, Bart, 2001, Opening Address, 18th Congress of the International Commission on
Irrigation and Drainage (ICID), Montreal, Canada.
Schultz, Bart, C.D. Thatte and V.K. Labhsetwar, 2005, Irrigation and drainage. Main
contributors to global food production. Irrigation and Drainage, volume 54, no. 3.
Ven, G.P. van de, 2004, Man-made lowlands. History of land reclamation and water
management in the Netherlands, 4th edition, Matrijs, Utrecht, the Netherlands.
UNCTAD, 2002. The Least Developed Countries Report. United Nations Conference on
Trade and Development, Geneva, Switzerland (www.unctad.org).
United Nations, Population Reference Bureau, The 2000 World Urbanization prospects.
UNDP Population Reference Bureau, 2005. 2005 world population data sheet, Washington
DC, USA.
Volker, A, 1987, Negative Side effects of Irrigation and Drainage, Gulhati Memorial Lecture,
13th Congress of the International Commission on Irrigation and Drainage (ICID),
Casablanca, Morocco.
World Bank, 2001. Global economic prospects and the developing countries, Washington
DC, USA.
World Bank, 2003, World Bank Atlas, 35th Edition, Washington DC, USA.
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The World Resources Institute, 1992, Towards Sustainable Development, World Resources
1992 - 1993, A Guide to the Global Environment, Oxford University Press, NewYork/Oxford.
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3 PRESENT AND FUTURE AVAILABILITY OF LAND AND WATERRESOURCES
Land and water resources are among the most basic elements of human life. In this chapter
some figures will be given about the present resources, the present use of these resources and
the future needs and availability of resources. It is of importance in view of the rapidly
growing population of the earth, the gradual improvement of the standard of living of a
considerable portion of the population and the deterioration of the resources. The
considerations will be focused on land resources but development of land resources to meet
the future needs cannot be carried out without the development of water resources.
The analysis that will be given is referring to global and regional entities. Because of the
uneven distribution of the resources and needs over the globe and within its regions this is not
sufficient for policy formulation and planning. This has to be carried out for much smaller and
more homogeneous areas such as hydrological units (river basins and sub-basins) and political
entities (international river basins, countries, and provinces).
3.1 LAND RESOURCES
The present agricultural area of the world amounts to some 1,500 million ha, which is 12% of
the total land area of 13,100 million ha. Presently irrigation covers more than 270 million ha,
i.e. 18% of worlds arable land. It is responsible for 40% of crop output and employs about
30% of population spread over rural areas. It uses about 70% of waters withdrawn from
global river systems. About 60% of such waters are used consumptively, the rest returning to
the river systems enabling its reuse downstream. Drainage of rainfed crops covers about 130
million ha, i.e. 9% of worlds arable land. In about 60 million ha of irrigated lands drainage
systems have been installed as well.
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Higher yields and higher crop intensities can only be obtained with a number of provisions,
which all require investments and entail financial problems. These are:
protection from floods; full control of water supply;
adequate irrigation and/or drainage;
advanced water management and cultivation practices;
optimum use of farm inputs;
institutional arrangements (irrigation and/or drainage associations with farmers
participation, credit systems and extension services);
modernisation of existing irrigation and drainage systems.
It is in these fields that the main obstacles are encountered in finding solutions for the future
food needs of mankind.
Land development
Land development may concern (Segeren, 1983):
reclamation of upland areas;
reclamation of lowland areas;
land consolidation.
Characteristic aspects of land reclamation
When reclamation is under consideration, the envisaged water management system and the
projected land use are of importance. The water management system depends on irrigation
and/or drainage requirements. The land use is mostly agriculture. However, lowland areas
might also be developed for urban expansions, new towns and/or industry.
Measures to be taken during reclamation of upland areas, to improve the texture of the soil
and to make it suitable for agriculture, refer to:
leaching of salts and toxic elements;
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erosion control;
terracing;
water harvesting.
Measures to be taken during reclamation of lowland areas, to improve the texture of the soil
and to make it suitable for agriculture, refer to:
lowering of the groundwater table;
leaching of salts and toxic elements;
soil improvement, by adding for instance lime;
application of chemicals;
landfill.
Related to the reclamation of lowland areas also the level of protection is of importance. The
level of protection depends on:
values inside the projected area: value of property and human life;
outside conditions, viz. sea, river, lake or canal.
Characteristic aspects of land consolidation
Land consolidation projects and programmes are generally executed in already cultivated
areas, which may have a long social tradition. These projects or programmes can only be
successful if they are developed and implemented in close consultation with the existing
population, which will normally also be the users. Generally these projects or programmes are
implemented at a smaller scale and over a longer time period than the land reclamation
projects.
3.2 WATER RESOURCES
Land development will not be possible without a proportionate development of the water
resources. Water is used for a great variety of purposes: irrigation and some special
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agricultural applications, domestic water, water in industries, navigation, recreation, and
nature conservation. In many areas there is an increasing competition between these
categories of users who have different requirements.
Water destined for irrigation occupies a special position among these categories, because it is
the largest item on the balance (70%) and this water is to a large extent irretrievable in that
most of this water does not return to the river like other withdrawals offering possibilities of
reuse.
Water resources development
Since more than 5,000 years people have tried to make use of water and to protect themselves
against it. Until about the seventeenth century various projects were implemented at a local
scale, without a clear recognition of the phenomena involved and of the side effects. Some
important events of the old history are shown in Table 3.1 (Biswas, 1972 and Postel, 1999).
The direct influence of mans water management activities concerns less than 1% of the water
resources, the fresh water lakes, watercourses, and groundwater (Table 3.2). However, the
side effects of mans activities influence almost all accessible waters on earth.
The hydrological cycle is the succession of stages, through which water passes from the
atmosphere to the earth and then returns to the atmosphere (World Meteorological
Organisation, 1974). Nearly all the precipitation falling on the land is derived from the
oceans. Only 10% of it originates from evapotranspiration from the land surface. Within the
hydrological cycle a cycle of water diversion, including water consumption through irrigation
and domestic water supply and drainage, exists. This branching cycle - expressing the
influence of man - is exerting significant influence on the primary hydrological cycle (Figure
3.1).
In studies on water resources development, water balances and possible changes by mans
activities play an important role. Several types can be distinguished, like the water balance of
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the earth, of the human-social sphere, of a river basin, or of a local area, like a city or a polder.
An important unit in water resources studies is the river basin. Water balances of river basins
may show large differences. Discharges range from less than 15% of the precipitation for theriver Nile in Egypt, to 70% for the Orinoco River in Venezuela. Initially, water balances and
the influence of mans activities were only studied from a water quantity point of view; in
some cases salt balances were made as well. Nowadays, there is an increasing requirement to
include all relevant quantity and quality aspects in water balance studies. These studies should
result in such an approach for land and water development projects, that they will be
technically and economically sound, and will result in a sustainable development and
exploitation of the concerned water resources (United Nations, 1992).
Table 3.1 Some recorded ancient hydraulic engineering events
(Biswas, 1972, Postel, 1999 and Fahlbusch, ed., 2001)
Date (BC) * Event
4000
3200
3000
2690 - 2950
2750
2200
1750
1700
1300
750
714
Irrigation in the plains between Tigris and Euphrates rivers in a place called Eridu
Reign of King Scorpion in Egypt. First recorded evidence of an irrigation system in
Egypt
King Menes constructed a dam along the Nile to protect the city of Memphis
Sadd-el Kafara dam built in Egypt probably for drinking water and irrigation. The
worlds oldest large dam
Origin of the Indus Valley water supply and drainage systems
Various waterworks of the Great Y in China
Water codes of King Hammurabi
Josephs Well near Cairo, nearly 100 m in depth
Irrigation and drainage systems in Nippur
Marib and other dams in river Wadi Adhanah in Yemen
Qanat system gradually spread to Iran, Egypt and India
* In the absence of accurate information, several of these dates are approximate
In relation to land and water development projects, the meteorological factors precipitation
and evapo(transpi)ration are of special importance. For precipitation this regards the annual
rainfall, the distribution over the year, and the short-term intensity. In case the difference
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between precipitation and evapo(transpi)ration is negative, it determines the need for an
irrigation system. In case of a surplus, it is decisive for the total amount of water to be
discharged. The short-term rainfall extremes are important in the design of drainage systems.Depending on the ratio between the rainfall intensity and the interception and infiltration
capacity of the soil, all the rainfall can infiltrate, or part of the rainfall is stored on the surface
and may cause overland flow. In the urban areas infiltration is much lower or even zero, as a
part of the soil is covered by streets, houses and squares, so there is a quick discharge.
Table 3.2 Amount of water on earth according to the survey conducted within the
international geophysical year (Holy, 1982)
Water incidence 103 km3 % of total
water
% of fresh
water
World oceans
Salt lakes and inland seas
Icebergs and polar ice
Water in atmosphere
Water in plants and living organisms
Fresh water lakesWater courses
Soil and subsurface water
Groundwater
1,300,000
100
28,500
12
1
1231
65
8,000
97.2200
0.0080
2.1360
0.0010
0.0001
0.00900.0001
0.0050
0.6200
-
-
77.630
0.035
0.003
0.3350.003
0.178
21.800
Fresh water total
Water total
36,700
1,337,000
2.7700
100.0000
100.000
-
With respect to groundwater, the unsaturated zone and the saturated zone can be
distinguished. The conditions in the unsaturated zone, like actual moisture content, wilting
point, field capacity and saturation are of importance for the growth of dry food crops.
Related to water management soils show a wide variety. For example, the average porosity
may range from 5% for limestone to 45% for clay, and the permeability from 10-4 m/day for
certain clay soils to more than 200 m/day for gravel. These differences influence the
suitability of the various soil types as well as the design criteria for field irrigation and
drainage systems.
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Evaporation
90%
Branching cycle
Land
interchange
Water vapour
Precipi-
tation
Water vapour in
atmosphere above land
Water vapour in
atmosphere above ocean
Ocean
Runoff
into ocean
Precipitation
Evaporation
10%
Intake of
water
Drainage
Water users
Water
consumption
Figure 3.1 Scheme of the hydrological cycle with the branching cycle, expressing the
influence of man (Rodda and Matalas, 1987)
All the rainwater that falls on the earth and is not evaporated, transpired, or withdrawn
artificially, contributes to the flow of the rivers. Dependent on different components, like the
size of the river basin, the slopes in the terrain and soil texture, the discharge to the river
differs. Depending on mans activities, the quality and quantity of water that enters the rivers
may differ as well. Rivers can transport natural, or artificial components. The load can differ
in relation to the discharge. Both quantity and quality of the river water will determine if it is
useful for irrigation or domestic water supply.
Table 3.3 indicates for 1990 and 2025 the estimated and projected volumes of available
renewable water resources and water use by continent. Table 3.4 shows the estimated and
projected global water use by sector in 1950, 1990 and 2025. As can be seen from the tables
on a global scale the use is only a small percentage of the resources and it seems that there is
still a considerable reserve to meet the future needs. However, since the resources are formed
by the river runoff not all that water can be used. Only a certain percentage can be abstracted,
the remaining has to be drained off to the sea during floods and a minimum flow to the sea
has to be maintained during other periods. On the other hand the possible contribution from
groundwater comes in addition.
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Table 3.3 Estimated and projected volumes of available renewable water resources and
water use by continent, 1990 and 2025 (Shiklomanov, 1997)Available renewable water
resources
Water use
Area 109
m3/year
m3/person
in 1990
m3/person
in 2025
1990
with-
drawal in
109 m3
1990
consump-
tion in
109 m3
2025
with-
drawal in
109 m3
2025
consump-
tion in
109 m3
Africa
North America
South America
Asia
Europe
Australia and
Oceania
4,047
7,770
12,030
13,508
2,900
2,400
6,180
17,800
40,600
3,840
3,990
85,800
2,460
12,500
24,100
2,350
3,920
61,400
199
642
152
2,067
491
29
151
225
91
1,529
183
16
331
836
257
3,104
619
40
216
329
123
1,971
217
23
World 42,655 7,800 4,800 3,580 2,196 5,187 2,879
For industrialised countries like France and the UK the annual water use is about 550 m 3 per
person. In these countries there is relatively little irrigation. In Egypt the only water supply for
agriculture is by water from the Nile corresponding with 1,200 m3 per person for year-round
irrigation and withdrawal of water for industrial purposes is only 5%. Assuming that in the
forthcoming five decades irrigation and industrialisation will expand all over the world it
seems reasonable to ascertain that as a world average the water use for all practical purposes
will be equivalent to about 1,000 m3 per person per year against the present figure of 660 m3.
Considering that the world population is supposed to double in fifty years and the readily
available resources are about half of the figures in Table 3.3 it is evident that on a global basis
the water resources will still be sufficient but that more or less severe water shortages may
occur in certain regions. These are North Africa (Maghreb and Egypt) and the Middle East
followed by Southeast Africa. In some regions such as North Africa and China and parts of
South America there is a growing competition for both land and water from the industrial and
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urban sectors. On the other hand there are regions where water resources will remain plentiful
for many decades to come, such as South America (Amazon) and Middle Africa. This,
however, will require regulations to cope with the uneven seasonal distribution of the riverflow. So far this has only been achieved on a relatively small scale.
Table 3.4 Estimated and projected global water use by sector in 109 m3 /year for 1950,
1990 and 2025 (Shiklomanov, 1997)
Item 1950 1990 2025
withdrawal consump-
tion
withdrawal consump-
tion
withdrawal consump-
tion
Agriculture use
Industrial use
Municipal use
Reservoirs
1,124
182
53
6
856
14
14
2,412
681
321
164
1,907
73
53
3,162
1,106
645
275
2,377
146
81
Total 1,365 894 3,580 2,196 5,187 2,879
World population in
millions
2,493 5,176 8,284
Irrigated area in 106 ha 101 243 329
More than 45,000 large dams and an estimated 800,000 smaller ones have been built around
the world, the major part in the period 1955 - 1990. The total effective capacity of these
basins is more than 5,000 km3, which is 12.5% of the runoff of all rivers of the globe
(ICOLD, 2006). This percentage is due to the fact that most of the largest rivers of the world
(Amazon with 18% of this total, Congo, Brahmaputra, Mekong, Orinoco) are not, or hardly
exploited. Much opposition exists for reasons of environmental concern, or resettlement
issues against building of new major dams.
3.3 REFERENCES
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Biswas, A.K., 1972, History of hydrology, 2nd edition, North-Holland publishing company,
Amsterdam/London, the Netherlands/Great Britain.
Fahlbusch, H., ed., 2001, Historical dams, International Commission on Irrigation and
Drainage (ICID), New Delhi, India.
Holy, M, Irrigation systems and their role in the food crisis, ICID bulletin, volume 31, no. 2,
July 1982.
International Commission on Large Dams (ICOLD), 2005. Data on web site: www.icold-
cigb.org
Postel, S., 1999. Pillar of Sand. Can the irrigation miracle last? W.W. Norton & Company,
New York, USA and London, Great Britain.
Rodda, J.C. and N.C. Matalas, 1987, Water for the future. Hydrology in perspective, IAHS
Publication no. 164, Proceedings of the Rome Symposium, April 1987, International
Association of Hydrological Sciences, Wallingford, Great Britain.
Segeren, W.A., 1983, Introduction to Polders of the World, Polders of the World, Final report,
International Institute for Land Reclamation and Improvement, Wageningen, the Netherlands.
Shiklomanov I.A., 1997, Assessment of water resources and water availability in the world.
UN report: Comprehensive assessment of freshwater resources of the world. St. Petersburg,
Russia.
United Nations, 1992, Agenda 21, chapter 18, Protection of the quality and supply of
freshwater resources: application of integrated approaches to the development, management
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and use of water resources, Conches, Switzerland.
World Meteorological Organisation (WMO), 1974, Guide to Hydrological Practices, 3
rd
edition, WMO publication no. 168, Geneva, Switzerland.
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4 CONCEPTS OF LAND AND WATER DEVELOPMENT
4.1 DEVELOPMENT APROACH
In general, land and water development projects have to fit into the development policy of a
country or a region. Land and water development projects may strongly differ in type and
scale. This refers to the reclamation and development of new areas, as well as to the
improvement of existing areas. Various development approaches can be followed. Distinction
can be made in:
large scale rapid development;
small-scale gradual development.
Another distinction in approach exists between:
directly based to the final stage;
step wise development.
For the different approaches it has to be taken into account that a project will have to follow
various stages, and should include the socio-economic and environmental consequences of the
proposed development.
4.2 DEVELOPMENT STRATEGIES
Different development strategies have been followed and may be followed in the
improvement of existing areas, or the reclamation of new areas (International Commission on
Irrigation and Drainage, 2005).
For the improvement of existing areas, the following aspects play a role:
role of the government;
determination of improvement options;
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consultation with the users;
institutional reforms and cost recovery;
land ownership.
Regarding the reclamation of new areas, the possible approaches regard the following aspects:
role of the government;
installation of the physical infrastructure;
identification of future users;
establishment of new institutions.
Improvement of existing areas
Role of the government
In the improvement of existing areas the government generally plays a guiding role during the
whole process. In the case generally different levels of government will have to co-operate,
with their different responsibilities.
Determination of improvement options
In