In the Stone Age, when people first began settling on the alluvial plains of Mesopotamia, perhaps their single most immediate concern was finding reliable sources of freshwater for drinking and watering their crops and animals. At first, the Tigris and Euphrates rivers and their tributaries, including the Upper and Lower Zab, offered the most obvious and convenient water supplies. And this is why so many of the early Ubaidian and Sumerian villages and cities were built on or very near the rivers. However, though they were important sources of life-giving water, the rivers, especially the Tigris, could be unpredictable and at times produced destructive spring floods. Periodic attempts were made to erect levees and dams to control the rivers, but ultimately the soft soil of southern Mesopotamia allowed these barriers to erode rapidly. Also, as populations grew, some people desired to build settlements in areas lying a few or even tens of miles from the nearest river. And the need to supply these new settlements with water presented another major challenge.
Canals To overcome these challenges, the early inhabitants of Mesopotamia steadily learned to supplement the direct tapping of the rivers with other water sources and supplies, including artificial canals, wells, and aqueducts. Canals—water channels dug on the surface of the ground— distributed water efficiently and safely and became vital to sustaining life in the region throughout ancient times. Their importance is reflected in a much-repeated ancient Mesopotamian curse: “May your canal become choked with debris!” By necessity, therefore, kings and other rulers made digging and maintaining canals a major priority. Any ruler who neglected
A stone bas-relief depicting the Elamite city of Madaktu surrounded by canals, dating from the 7th century b. c. Erich Lessing/Art Resource, NY
The existing canals was certain to become unpopular and risk inciting unrest or even rebellion. It is not surprising, therefore, that the famous Babylonian king Hammurabi spent the better part of the last nine years of his reign (ca. 1792-1750 b. c.) building irrigation canals. Because constructing a canal was a massive undertaking, a ruler like Hammurabi called on large numbers of his subjects to do the job. In some times and places, slaves did some of the work; however, most of the laborers on such projects were free people who were working off part of their tax obligations to the government.
In the actual construction of such irrigation canals, the main challenge was making sure that the bed of the waterway had the proper slope. The channel had to slope downward slightly as it moved away from the river to take advantage of gravity and thereby make the water flow. If the slope was too little, the water would stagnate from a buildup of silt; by contrast, if the slope was too great, the water would flow too fast and erode the channel’s bed. Even when the slope was just right, silt slowly but inevitably built up, and the beds and banks of the waterway slowly but surely deteriorated. Thus, regular maintenance was required. The first-century b. c. Greek geographer strabo describes it this way:
There is need of much labor to keep them [the Mesopotamian canals] up, for the soil is so deep and soft and yielding that it is easily swept out by the streams, and the plains are laid bare, and the canals are easily filled, and their mouths choked, by the silt.
... The aid required is this: to prevent most of the overflowing [and] filling up effected by the silt. . . by keeping the canals cleared and the mouths opened up. ... [It] requires the work of many hands; for, since the earth readily gives in and is soft, it does not support the silt that is brought upon it, but yields to the silt, and draws it on, along with itself, and makes the mouth hard to dam. (Geography 16.1.10)
Once the canal had been dug, a sluice gate constructed on the bank of the river controlled the volume and flow of the water into the artificial channel. When deemed necessary, the gate was opened or closed the desired amount, thereby increasing or decreasing the water’s flow.
Such a sluice gate was only effective, however, when the level of water in the river was normal. At those times when the level dropped below that of the gate, the flow of water into the canal stopped. To overcome this problem, some bright, anonymous ancient Ubaidian or Sumerian got the idea for a device that the Arabs later called a shaduf. It consisted of a long pole with a bucket attached to one end; there was a counterweight attached to the other end of the pole, the center of which rested on a fulcrum, such as a rock or a block of wood. Depending on the size of the shaduf, one or more people operated the device by swinging the pole on the fulcrum so that the bucket dipped into the river and filled. Next, they swung the device up and over the bank of the canal and emptied it into the canal. The shaduf was also used to move water from one canal to another. The Greek historian Herodotus saw this device in action when he visited Babylonia in the fifth century B. c. “The rainfall... is slight,” he reports,
And provides enough moisture only to burst the seed and start the root growing, but to swell the grain and bring it to maturity, artificial irrigation is used, not, as in Egypt, by the natural flooding of the river, but by hand-worked [shadufs]. Like Egypt, the whole country [i. e., region of Mesopotamia] is intersected by [canals and] dykes. The largest of them has to be crossed in boats and runs in a southeasterly direction from the Euphrates until it joins another river, the Tigris. (Histories 1.193)
Wells Hand-dug wells were another important source of freshwater in ancient Mesopotamia, especially in the northern plains where the Tigris River was more difficult to control and the soil was denser. At first a typical well was simply a deep vertical hole in the ground; a person lowered a bucket on a rope, dipped the bucket in the water at the bottom, and pulled it up. This process was made easier by the introduction of the pulley in about 1500 B. c. or slightly earlier. Another improvement came in the reign of the Neo-Babylonian king Nebuchadnezzar II (ca. 605-562 b. c.). His engineers attached many pulleys and buckets to a long chain connected to a winch, and when the winch was turned the chain carried the buckets out of the well, over a basin where the water poured out, and back to the well, all in a continuous loop.
Aqueducts Aqueducts were still another source of water in Mesopotamia. An aqueduct is an artificial channel that carries water from one location to another, usually underground. Herodotus told the story of a sixth-century b. c. Arabian ruler who made such a water channel out of animal skins. Supposedly it was 300 miles (483km) long. Although this smacks of fable, or at least is surely exaggerated, that technique was used to transport water for short distances in some parts of the ancient Near East. A more stable and durable kind of aqueduct consisted of a tunnel excavated belowground. As in the case of irrigation canals, the proper slope of an aqueduct was the key to its success. It had to tilt enough so that water flowed away from its source (a river, stream, or lake), but not too much, or else the water would flow too fast and erode the channel. The first underground aqueducts in Mesopotamia were built during the reign of the Assyrian king Sargon II (ca. 721-705 b. c.). Sargon invaded Armenia (Urartu) and there saw a system of aqueducts the locals had constructed. He destroyed these, but on his return home he ordered similar water channels to be dug in Assyria.
After Assyria’s fall, the Persians adopted and expanded the Assyrian system of aqueducts. These were located mainly in northern Mesopotamia, where the ground is reasonably firm; the alluvial soil in southern Mesopotamia was too soft to make underground aqueducts practical. The Persians called an aqueduct a kariz, but the later Arabic term qanat became much more common and remains in use today.
Later the Romans became famous for building similar but better-constructed and more extensive aqueducts in many parts of the ancient world. One major reason that the Roman versions were superior to those of Mesopotamia was that the Romans had access to large quantities of solid, durable stone to line the channels. They also used the stone to build special bridges, called arcades, to carry the water channels aboveground when it was necessary to ford streams or ravines. Lacking significant supplies of stone, the Mesopotamians were unable to erect such arcades. The only known exception was a bridge erected by Sargon’s son, Sennacherib (reigned ca. 704-681 b. c.), to carry a water channel across a small river valley near Nineveh.
The Fate of Mesopotamia’s Water Supplies These water suppliers and conveyors— canals, wells, and aqueducts—combined to create huge amounts of freshwater for use across many parts of ancient Mesopotamia. This allowed local cities to support large populations and increased the size of arable lands, which resulted in the production of enormous quantities of crops. In the best times, southern Mesopotamia alone had an estimated 12,000 square miles (31,000 sq. km) of irrigated farmland. This may seem incredible when one looks at modern Iraq, which has far less arable land and must import much of its food. The question naturally arises: What happened to the complex and far-reaching water supplies that the ancient Mesopotamians spent millennia developing and maintaining?
One part of the answer is neglect. The Greek Seleucids carefully maintained the old canals and aqueducts. But the Parthians, with their decentralized, feudal administrative system, left such maintenance up to local lords, and many of them allowed the canals under their care to deteriorate. The next group of rulers who inherited the region, the Sassanians, spent most of their resources maintaining Iran and tended to neglect the Mesopotamian plains overall; so in this period the canals
Relief detail from the temple of Ishtar in Mari, Syria, from 2400 b. c. depicting a victory parade of Mesopotamian soldiers carrying battle-axes. Erich Lessing/Art Resource, NY
And aqueducts suffered further disintegration. Purposeful destruction also took a toll, as various foreign conquerors destroyed the canals, as sargon had wrecked the Armenian ones, in an effort to defeat the local Mesopotamians. The worst offenders were the Mongols, a tribal people from central Asia who invaded Mesopotamia in the thirteenth century a. d.
Finally, nature slowly but surely acted to erase Mesopotamia’s ancient waterworks. The region’s rivers occasionally changed course; silt and vegetation clogged sluice gates, canals, and qanats; and salt deposits from evaporation of lakes and parts of the Persian Gulf made it increasingly difficult to germinate seeds even in the remaining well-irrigated regions. Ironically, cameras aboard modern satellites have revealed the locations of many of Mesopotamia’s ancient water channels that are dried up and no longer visible at ground level.
See Also: farming; Sennacherib; taxation; Tigris and Euphrates; Zab rivers
World History
