A Water Story

Learning from the Past, Planning for the Future

Geoff Beeson

• Publisher: CSIRO PUBLISHING
• Year: 2020
• Print ISBN: 9781486311293
• eBook ISBN: 9781486311316
• Topic: Scienze fisiche
• Subtopic: Storia mondiale

Freshwater scarcity is a critical challenge, with social, economic, political and environmental consequences. Water crises in Australia have already led to severe restrictions being applied in cities, drought ravaging farmlands, and the near-terminal decline of some rivers and wetlands.

A Water Story provides an account of Australian water management practices, set against important historical precedents and the contemporary experience of other countries. It describes the nature and distribution of the country's natural water resources, management of these resources by Indigenous Australians, the development of urban water supply, and support for pastoral activities and agricultural irrigation, with the aid of case studies and anecdotes. This is followed by discussion of the environmental consequences and current challenges of water management, including food supply, energy and climate change, along with options for ensuring sustainable, adequate high-quality water supplies for a growing population.

A Water Story is an important resource for water professionals and those with an interest in water and the environment and related issues, as well as students and the wider community.

1

Water and the earliest civilisations

The stunning water engineering achievements of the ancient Roman civilisation, such as imposing aqueduct bridges and grand public baths complexes, are familiar to most of us. Some 2000 years ago, they were parts of sophisticated water management systems for Roman cities and towns. Even older civilisations, as far back as 7000 years, made impressive achievements in managing their water, mainly for irrigating farmland. These include the ancient Egyptians and civilisations in Mesopotamia and the Indus Valley. Although these are vast periods before our own time, they are dwarfed by the tens of thousands of years during which the Australian Aboriginal peoples managed the available water sustainably to meet their needs.

Ancient Australia

The remarkable achievement of the Aboriginal peoples of Australia was to continue to live sustainably in the land over a period of more than 50 000 years, perhaps as long as 65 000 years. They lived throughout the country, from the tropical north to the cool Tasmanian south; from the western plateau to the eastern highlands; in hill country and on the plains; in deserts and in well-watered lands. They adapted to extraordinary climate change and lived through drought and flood. Their achievement was not dependent on building large water-engineering works, but on managing the landscape in a systematic and meticulous way to ensure there was abundant food and water available, despite the dramatically variable Australian climate. Several factors were fundamental to their success, including their detailed knowledge of the characteristics, requirements and tolerances of plants and animals; careful protection and husbanding of available water resources; development of water storages, including wells and dams; and their making of smaller scale modifications to streams and wetlands as well as broader scale modifications to the landscape. Knowledge and experience were passed down through the generations as part of Aboriginal Lore, which prioritised and protected water places. This approach enabled the Aboriginal peoples to live in harmony with the environment; it did not lead to degradation, such as through erosion or salinisation, or need periodic corrective measures to maintain the system.¹

These matters are discussed further in later chapters, especially Chapter 6.

Water management in ancient worlds: irrigation, canals, cities

Irrigation was one of the earliest forms of water management and distribution, stretching back thousands of years. Examples can be found in ancient Egypt, Mesopotomia, the Indus Valley and China, but are not limited to these cultures. Some early civilisations developed ingenious methods of supplying large cities with water, including those in Assyria and in the Indus Valley.

Egypt: the Nile Valley

The Egyptians began practising some form of water management around 3000 BC (though there is evidence of farming before 5000 BC). In ancient Egypt, the Nile River was the key to life because there was (and still is) very little rainfall in that country. The river flooded each year with predictable regularity, with all of the water coming from outside the country, most of it from the Ethiopian Highlands. Once the waters had receded from the wide floodplain, wheat and other crops were planted in the now well-watered soil, which was also fertilised by the rich silt carried down from the highlands. Egyptian farmers developed a style of water management called basin irrigation, which was dependent on the natural rise and fall of the river. They built networks of earthen banks, some parallel to the river and some perpendicular to it, thereby forming flat-bottomed basins of various sizes, into which floodwater could flow via regulated sluices. The water was allowed to stand in the basins for 1–2 months and was then drained off downstream back into the river when the time came for planting the crops.

With the river flooding reliably, there was always plenty of water. Increasing soil salinity was not a problem because the month or two of inundation took any salts that had accumulated in the upper soil layers down to below the root zone (see box: ‘Requirements for sustainable irrigation’). Consequently, the irrigation practised along the Nile was not only productive but sustainable – it lasted for 5000 years. However, not all was perfect: a low flood could lead to famine, and a high flood could destroy dykes and other earthworks. Knowing the height of the Nile flood in advance was critical to the success of the irrigation system. Early on, the ancient Egyptians developed a system for measuring the height of the Nile at various points along the valley. ‘Nilometers’ were structures made of stone and of various designs, such as a marked column submerged in the river’s edge, a stairway leading down to the water with graduations on the walls or a more complex design.²

A clear advantage of being able to direct the flow of water onto the fields was that no lifting of the water was required. However, there were places where fields were too high to receive water from the river or canals. The shaduf, a water-lifting device, appeared in upper Egypt sometime after 2000 BC and was already in use in Mesopotamia. It consisted of a bucket on the end of a cord that hung from the long end of a pole which swung from a pivot and was counterweighted at the shorter end. It allowed farmers to irrigate crops near the river or canal banks when the water level was low during the dry season. Use of the shaduf led to an increase in the area under cultivation of 10–15 per cent. The shaduf was later supplemented by the noria, a waterwheel with attached pots for raising water.³

More than 25 centuries after the beginning of irrigation in Egypt, Herodotus, referred to by his admirers as the ‘father of history’, visited the country and commented on the role of the Nile. Writing in the fifth century BC, he reported that ‘when the Nile overflows, it floods not only the Delta but parts of the territory on either side … to a distance of two days’ journey – in some places more, in some less’. He also referred to the ‘innumerable dykes, running in all directions, which cut the country up’, and consequently made the country ‘unfit for horses or wheeled traffic’. He described how the purpose of the dykes had been to supply water to towns which lay inland at some distance from the river. He also believed that the people of the lower Nile ‘get their harvests with less labour than anyone else in the world’.⁴

According to fresh water expert Sandra Postel,² the early Egyptian irrigation works were not centrally managed, unlike in other ancient civilisations. It appears that water management was carried out at the local level, with decision-making and responsibility close to the farmers. She suggests that this may have been an important factor in the continuity and longevity of the basin irrigation system as the farmers might well have been able to continue their irrigation practices while political disruptions and wars engaged the state bureaucracy. The basic simplicity of the system was also a factor; substantially less labour and maintenance were required than in other irrigation networks such as those of Mesopotamia.

Requirements for sustainable irrigation

For a region to be irrigated on a long-term basis, it has to have

• an abundant supply of water

• well drained soil

• good drainage through the region

• a supply of fertiliser for the soil.

One of the greatest threats to the long-term sustainability of irrigation in a region is increasing soil salinity. River water is never pure, as it contains dissolved mineral salts. Evaporation makes it saltier. As water flows out over the soil in a thin sheet during irrigation, it evaporates and consequently becomes more saline. If the water dries up altogether, it may leave a thin layer of salts on and in the soil. In addition, plants absorb moisture from the soil, thus leaving the soil more saline. All of these processes contribute to the salt build-up in the surface layers of the soil until the area becomes too saline to support the growth of crops and pasture.

The only way to overcome this problem is to apply enough water to flush the salt off the surface or through the soil. Unless the salt is flushed away completely from the region along natural or artificial drainage channels, the salt will just be shifted to another area, including possibly to downstream users or into groundwater.

Flushing also leaches out soil nutrients, which must be replaced for agriculture to be sustainable.⁵

Mesopotamia

In Ancient Mesopotamia (‘land between the rivers’), civilisations relied on the life-giving properties of two rivers – the Tigris and the Euphrates. The rivers run roughly parallel to each other and formed the western (Euphrates) and eastern (Tigris) boundaries of Mesopotamia, located in present-day Iraq, mostly, but also parts of modern-day Iran, Syria and Turkey. (Today, the rivers join before emptying into the Persian Gulf, but in ancient times the sea came further inland, and the rivers emptied into the sea separately.) The plains between the rivers were dry, with little rainfall, but they were fertile, especially near the rivers. Unlike the Nile, the Tigris and the Euphrates could be wild and turbulent, and floods were frequent, meaning a different approach to tapping and using the waters was needed.

Important ancient civilisations in Mesopotamia included the Sumerians in the south, the Babylonians in the central and southern areas, and the Assyrians in the north.

The Sumerian civilisation

The Sumerian civilisation lasted from ~5000 BC to 1750 BC. Sumerians were sowing and harvesting in southern Mesopotamia in the fertile soil just north of the Persian Gulf by ~7000 BC, and practising irrigation before 4000 BC. Communities of farmers dug tanks and reservoirs to store water, and built ditches to lead the water to their fields during the growing season. Over time, these simple arrangements were extended and developed into more sophisticated systems involving networks of dams, reservoirs, canals and drainage channels, enabling farmers to grow their crops outside the short rainy season. Crops included wheat, barley, onions, turnips, grapes and apples, and people kept cattle, sheep and goats. The consequent increase in productivity meant that food could be stored for use in leaner seasons or be used in trade for needed goods not available in the area, such as stone for tools, decorations and weapons.

Increased productivity also resulted in the population increasing greatly during the period 6000 BC to 4000 BC, based on irrigation of the fertile soil that had been deposited by the Tigris and the Euphrates over millennia. Cities of thousands or even tens of thousands of people developed. It is also interesting to note that these people fought over water rights, a source of conflict that has repeated down through the ages.⁶

The Babylonian civilisation

The Babylonian civilisation endured from the eighteenth to the sixth century BC. The Babylonians inherited the technical achievements of the Sumerians in irrigation and agriculture, maintaining and extending the system of dykes, canals, weirs and reservoirs constructed by their predecessors. The maintenance work required was considerable – canals became blocked with silt brought by the rivers, and floods had the potential to destroy dykes and weirs.

Herodotus records the work of two Babylonian rulers in modifying the course of the Euphrates River, which divided Babylon in two. Around 600 BC the queen Semiramis ‘was responsible for certain remarkable embankments in the plain outside the city, built to control the river which until then used to flood the whole countryside’. Five generations later, queen Nitocris had changes made to the river in order to improve the security of the city. By cutting channels upstream she caused the river to wind through the city instead of running straight. She built high embankments on both sides of the river, and she had a basin dug for a lake ‘some forty-seven miles in circumference’. These were all designed to slow the flow of the river and to make life difficult for invaders.⁷

Assyria

Assyria existed as an independent state from ~2500 BC to 605 BC. The highpoint of the Assyrian’s achievements in water management was truly remarkable, and was reached under King Sennacherib in the late eighth and early seventh centuries BC. Sennacherib had a vast network of canals built in four stages, into which half of the water from a river flowing from the Zagros Mountains was diverted. The remains of this system can still be seen. Evidence includes inscriptions of the king himself, written in cuneiform texts on clay tablets and on the irrigation features themselves, and remnants of weirs, canals and aqueducts visited opportunistically by travellers and archaeologists since the 1850s. More recently, Jason Ur, a professor of anthropology at Harvard University, has examined the canal networks using recently-declassified intelligence satellite photographs taken by the United States in the 1960s and early 1970s and low-level aerial photographs acquired by a private firm in the 1950s.⁸

The first stage, a canal 13.4 km long and leading to Nineveh, the new imperial capital, was commenced in ~702 BC and would have irrigated ~12 km² of land. The final stages, which included the true engineering achievements, were completed ~690–688 BC. Two basic forms of canal were built: earthworks constructed across a watershed to direct the water flow, and channels 6–20 m wide and 2 m deep, their course dictated by the local terrain. Altogether, more than 100 km of canals were constructed, having a rock or pebble bottom so that the water flowed clear, and there were tunnels, weirs, reservoirs, and takeoffs for irrigation. The longest canal, the stage four Khinis canal, stretched 55 km across the parched countryside from Kh...

Table of contents

• Cover
• Title
• Copyright
• Contents
• Foreword
• Acknowledgments
• Challenges and opportunities
• 1. Water and the earliest civilisations
• 2. Water use across the Roman Empire
• 3. Some basics about Earth’s water
• 4. Water supplies for the First Fleet colonists
• 5. The search for water inland
• 6. Aboriginal Australia
• 7. The Great Artesian Basin
• 8. Groundwater: more than the GAB
• 9. Kati Thanda–Lake Eyre and its basin
• 10. The golden pipeline
• 11. Adding water to the land: irrigation
• 12. Dams and reservoirs: storing water
• Colour plates
• 13. The Murray–Darling Basin
• 14. Saving the Murray–Darling Basin?
• 15. Water for cities, towns and farms
• 16. Living with scarcity
• 17. Facing the future
• Glossary
• Appendix I: Case Study: South Australia’s long-term water plan
• Endnotes
• Index