The Physical Elements

Three primary factors must be known about Iraq before any physical, human or economic elements can be sorted and evaluated. Information about where Iraq is, how large it is, and what shape it has is essential at the beginning of such geographic study. Each plays a significant role in the geography of the country and the region as a whole.

A. Location

Iraq, in terms of latitude and longitude, lies between 29°15’N, and 38°15’N, 38°45 and 48°45 E. That means it is located entirely within the north temperate zone where it enjoys stimulus seasonality of climate.

The country is bounded by several Arab and non-Arab States: Turkey on the north, Iran on the east, Syria and Jordan on the west and Saudi Arabia, Kuwait and the Arab Gulf on the south. Throughout history, Iraq’s inhabitants have entered into peaceful relations with their neighbours, and their civilization originally based on agriculture should gradually have given way to one in which trade had a major part. This is more true at the present time. With an immense agricultural and mineral wealth, there is no necessity or inducement not to assert the same historical relations. There is no need to speak about the brotherly ties that bind Iraq with the surrounding Arab states and its sincere efforts for Arab aspirations to become true.

At the regional and global levels, Iraq has had extraordinary importance since its early days. Its location is at the meeting place of Asia, Africa and Europe, and along the shortest land span between the Indian Ocean and the Mediterranean making Iraq on of the pivot area in the world.

The Euphrates and the Tigris not only supplied water for irrigation and man’s more immediate personal needs, but were also used for movement, which is always along the lines of least resistance. It was comparatively easy to pass from Mediterranean shores across the Euphrates.

With the advance of civilization and as the conditions of living improved, the location of Iraq has become an increasingly important. Modern land roads are crowded with vehicles carrying goods from far away places to various destinations. Clear blue skies are crossing-points for international air routes.

B. Area

Iraq has a total area of 438,317 square km. The extent of its national territory, compared with that of European countries, exceeds all but the former Soviet Union, France and Spain.

Gifted with a variety of natural resources, it can support a large population and enables the country to attain its maximum strength. The land is able to produce its fruits on greater scale than in the past, and Iraq will be as prosperous as ever.

C. Shape

The shape of the area is an advantage to Iraq. It has almost an ideal circular plan, and Baghdad, the capital city is located at the centre. Such a compact shape is an asset from the point of view of economic, cultural and national unity. This has helped to minimize the difficulties of travel, to decrease diversity of physical environment and the length of the boundary to be guarged. It is unusually easy to travel in Iraq. No more than a few hours are needed to travel by car from Baghdad to any place in the country.

D. Climate

Lying in land, continental extremes are climatic characteristic in Iraq. Dry and hot summers and cooler wet winters are the main features. For the most time of the year, Iraq is under the influence of high pressure, with northerly dry and warm winds. In summer, this steady air movement from the north and northwest, forms a hot, dry wind which often blows.

In winter, this inflow is frequently interrupted by cyclonic activities, a part of the irregular westerly circulation of middle latitude which dips southward with the oscillation of the subtropical high pressure belt in the direction. The yearly average number of these east moving cyclones amounts to 120. Most precipitation is associated with these weak cyclones.

Occasionally, a well -developed cyclone may remain stagnant over the country for several days. This draws in large amount of maritime air associated with considerable amount of rain lowlands, and heavy snowfalls in the mountains. In general, there is gradual rain increases in a north east direction, from 50mm in the south-western corner to a 1000mm in the high mountainous area of the northeast. In the latter areas, precipitation is influenced by a combination of cyclonic activity and orographic barrier. The 200 mm line is an important line. This isohyet, in general, indicates the southern limit of the rain-fed agricultural zone. But the annual variation of the rainfall is very high, and the southern limit of the rain-fed agricultural zone dose not have a fix position. Some winters are dry, while others are much wetter. Accordingly, isohyets shift to the north east in dry years, and to the south-west in the wet ones.

Time and geographic variation of rainfall are important factors for dry farming. Some additional rain in spring can favourably influence the yield of wheat and barely. There are also differences in the monthly rainfall data. The number of rain days in Basra, Rutba, Baghdad and Mosul are 51,55,48 and 59 respectively.

Temperature

A large daily and annual temperature range is a pronounced continental climatic characteristic. The annual average temperature in Baghdad is 22.5° C while the mean daily minimum temperature in January is 4° C the mean maximum of temperature in August is 43.2° C.

The air humidity is rather low. In Baghdad, the relative humidity in August ranges from 44 percent at the highest to 21 percent at the lowest. With clear days ranging from 198 in Mosul to 207 in Baghdad, Iraq is an area of high thermal energy, and an intense solar energy becomes a renewable national resource. A long growing season (frost-free period) enables the country, with available water resources, to grow almost anything that can be grown in middle and lower latitudes.

Climatic Types

The climate of Iraq, in terms of temperature and rainfalls, may be classified into three main types.

Mediterranean Climate

This type is characterised by cool, wet winters, and hot, dry summers. It is more restricted to the mountainous areas. Therefore snowfall is not uncommon, and the amount of rainfall varies from 400mm at the lower area to 1000mm on highest ones. The average summer temperature doses not exceed 35° C on the lower slope s, but it is much less on the higher slopes.

Steppes Climate

This type is transitional one between the Mediterranean type in the north and the desert in the south. High temperature and small amount of rain are the main limiting factors. Rainfall range between 200mm to 400mm. It comes during the cool season of the year where the evaporation rate is the lowest. This is a natural pasture area for a large number of sheep flocks.

Hot Desert Climate

Lowlands in Iraq are a hot desert. This is an area of a high thermal energy. With clear air in summer, solar isolation becomes intense, and air temperature rises to a maximum of 45-50° C. the daily range of temperature is very large. Nights are rather cool, and the people find it very refreshing to sleep in the open air. In winter times, warm and sunny weather prevails, and the temperature rarely drops under freezing point.

E. Physiography

Mountains, plateaus, hills and valleys, planes and inland water-covered areas are the major geomorphic forms, which, in varying combinations, make the topography of Iraq. These geomorphic forms exert a strong influence upon the cultural and economic patterns of the country and, together with the climate, provide a permanent back-drop against which the history of Iraq is enacted. It is very interesting to find in a limited area, like that oIraq, good example of land forms of the earth's surface.

Iraq, together with the Arab Gulf, is a down-dropped block, like that of the Red Sea, trending also in the same direction. The country was lying, millions of years ago, in a shallow sea. Marine sediments, mainly limestones, were deposited, and streams from the surrounding land surface brought alluvium deposits into it. Thus, the sea area became gradually restricted.

A mountain movement starte50 to 30 million years ago, and a series of sedimentary beds, lying at the bottom of the shallow sea, has been regularly bent into arches and troughs, that is, into anticlines and synclines. The arches formed the mountains, and troughs formed the valleys. The mountain building movement is still going on, but a very slow rate.

During the three main pluvial periods in Iraq, associated with glacial ages in Europe, climate was more humid than at present and a considerable period of river erosion modified the land surface. The mountains were cut down and the valleys as well as the southern part of the extensive geocycline were filled up with pebbles, gravel, sand, silt and clay. Inter-pluvial phases, with a climate similar to that of the present time, interrupted the erosional process, and river terraces have been formed along the rivers and their tributaries in central and northern Iraq. Three broad erosional river terraces, for example, can be seen in Tikrit along the eastern banks of the Tigris.

Four broad topographic regions, in terms of area altitude, can be distinguished in Iraq. They are:

Mountain Region

Bold, majestic mountain scenery covers an area of 92,000Km or about 21 percent of the total area. It extends mainly in the northern and north-eastern parts of the country. The mountains consist mainly of parallel anticlinal ridges separated by elongated synclinal valleys. But they are united by narrow gorges, the outlets of the drainage of the interior basins. The mountains for the greater part are eroded, and the detrital material has been deposited in the valleys and in the area in front of the mountains. The mountains consist of various folded limestone layers varying from simple foldings in the south to complicated foldings in the north. Sindy, Zab and Rawandooz geosycline separates them. The average elevation of the former area ranges from 5,000 to 6,000 feet, while it reaches an elevation of 7,000 to 10,000 feet in the complicated folded one. Faults, metaphoric rocks and glacial landforms are not uncommon in this area. The highest mountain peak in the country is Hassarrost, it stands 3,607 meters above sea level.

Water-falls, casades, rapids and deep gorgeo are common geomerphic phenomena in the area. Plains of a considerable size, such as Rania and Shahrazoor, separate two mountain areas. The former, is a kidney-shaped plain, in the Lesser Zab area, with an elevation ranging from 1,600 to 2,000 feet. It extends for 30 Km and its width varies from 20 to 30 Km. A basin-like Shahrazoor plain varies in elevation from 1,500 to 2,000 feet above sea level. From east to west, Shahrazoor extends for 45 km, but it narrows down to 50 Km in the north-south direction.

Natural vegetation in these mountainous areas reflects in a very clear way local climatic conditions. The lower treeeline has thermal and rainfall limitation. It is found in areas about 1,000 meters high and with an amount of annual rainfall not less than 500. Juniper trees draw at the upper parts of the forest belt, while maple, walnut, ilmond and ash trees are widely grown at the middle altitudes. The pistachio and olive trees thrive in dryer places. The inner treeline is more restricted to areas of 1,500 meters above sea level, and the annual amount of rainfall is not less than 500 mm. Alpine graces grow at higher elevations. These are natural grazing areas for large herds of sheep and goats. In summer times, shepherds, following the slow melting snow, may drive their herds as high as 9,000 feet. This can be seen on the slops of Hassarrost mountain north-east of Rawandooz. In the fall, the process of migration is reversed.

Agriculture of extensive type is dominant in the lowlands. Arable lands in Rania and Shahrazoor plains are mainly fields of wheat and barley in winter. While mixed intensive farming is the major practice during the rest of the year, vegetables, fruits, sugar beet and diary products are becoming the main cash crops in the area.

Cool climate. Snow-clad peaks, deep river valleys, forested slops and water falls provide a very good bases for thriving resorts. Long and hot summer months encourage a large number of people from the cenrte and southern parts of the country to travel northward. Here they may enjoy a refreshing cool weather and relax beside a charming mountain scenery. Some of these places have their charm even in winter times, such as Haj Umran (Arbil Province) a resort located on the side of Hassarrost mountain at about 1,780 meters above sea level. The temperatures in winter may drop sharply as low as 15 degrees centigrade below zero. Nearby smooth and gentle slopes, covered with powdery snow make them ideal for skiing and other winter sports.

Undulating Lands

A fairly hilly landscape located south and west of the mountain region. It covers an area of about 42,000Km, or nearly 9.6% of Iraq's total area. Although there are some similarities with the former region, general landscape differences stand sharp. The area is somewhat folded in the later phase of folding. It consists of low parallel hill ridges, wide shallow valleys and extensive plains, in which various streams have cut their valleys. In general, average altitude varies from 200 to 1,000 metres. Local relief is more than 500 feet per square kilometer, but less than 2,500 feet. Beds of gravel, conglomerate and sandstone make up the area. It can be divided, in terms of geomorphic landforms structure, surface rocks and degree of erosional process, into a number of plains, plateaus, mountains and hill ridges. A briefly discussed example of each may summarize the whole picture of the region.

The mountains are relatively low. Sinjar, is an anticlinal range, extending in a north-easterly direction. Its elevation varies from 4,800 to 2,800 feet. The southern edge of the mountain range is a highly dissected part. Strike valleys and minor scraps are common.

Plateaus are small in number, and the best known are those of Mosul and Kirkuk. The surface of Mosul plateau is dissected by shallow valleys with hills rise to 1,000 feet above the surrounding valley bottoms.

Plains are found within the area such as the plain of Sinjar and Arbil. The latter is a synclinal triangle basin filled with alluvium deposits. Its elevation varies from about 1,800 feet at the eastern edge to 1,000 at the western parts. Fertile soils together with an adequate amount of winter rain provide a good basis for agricultural land use. Wheat and barely are the main crops in winter, while underground water resources supply enough irrigation water for many agricultural products during the other seasons.

The economic importance of this region may be summarized as follows:

Mineral wealth, mainly oil and sulphur: large oil fields are found in Kirkuk are and Ain Zalah, while sulphur deposits are mined in two major areas namely, Al-mishraq and Fatha.

Agricultural products, such as wheat, barely, sugar beet, cotton, vegetables, fruits and dairy products, from the basis of a solid agricultural economy.

During the winter a significant growth of annual grasses and legumes, depending on rainfall, provides good natural pasture lands. Sheep and cattle raising industry is widely-spread throughout the area.

Agricultural industries (sugar, cotton and woolen textiles, diary products, cigarettes, etc.) enjoying special government attention are found in different localities throughout the region.

3. The Depositional Plain

It is the plain of the twin rivers, the Tigris and the Euphrates, referred to in ancient as Shinar and later on was called Asswwad, because of its high agricultural productivity. The plain is located in central and southern Iraq with a numbeof distinct landscapes. The undulating lands are to the north, the western plateau to the west, Zagros mountain to the east and the Arab Gulf to the south. The plains (including marshland and lakes) cover an area of 132,500 Km or 30.2 of the total national area. It has a northwest-southeast orientation, trending in the same direction of the Tigris, Euphrates and Shatt al-Arab.

Geologically, the plain occupies the southern part of an extensive geosycline. It was filled up by sedithe rivers brought in during the quarternary and recent geological periods. Besides the fluviatile sediments which are carried by the twin rivers, some material of aeolian origion, blown out of the desert, is accumulated and mixed with fluviatal deposits. As a result of flood and irrigation, rather thick layers of mud have been deposited on top of the original soils. Nearly the whole plain is now covered by this silty material.

The elevation of the region increases gradually from south to north. From mud at sea level along the Arab Gulf coast, to more than 32 metre around Baghdad, a distance about 654 Km away. But the increase is rather sharp in a west-east direction. The elevation increase from 5 metres above sea level, at the basin-like area north of Basra, to 100 metres in both directions within a much shorter distance.

Along the eastern borders, rivers tumbling down from the eastern mountains helped to form a number of alluvial fans. A series of adjacent fans coalesced to form an extensive piedmont alluvial plain. The material comprising these fans varies in texture, from coarse boulders and pebbles at its head to find material down its slope. On such alluvial fans Mendile and Badra are located. Here is a good example of a successful agricultural land use. Gentle slopes, fertile loamy soils, good air drainage in winter and flow irrigation were utilized in an excellent way to grow date palms and citrus fruits.

Most of the plain appears to be dead flat. In areas away from rivers or cultivated land, one may look to the full circle of the horizon without seeing any perceptible slope. But natural levees, irrigation canals, low lying hills may break the monotony of the land.

Rivers flow with a gentle gradient and are unable to carry all their load of sediment. For this reason, natural levees capped with dikes border the Tigris and Euphrates. Flow irrigation canals can be easily led away from the rivers. Many parts of the plain have poor drainage, especially in the basin-like area in its southern part north of Basra.

Marshlands occupy an area of more than 35,000 square Km. Their geographic distribution may be seen in three distinct bells. One east and west of the Tigris, the other is Al-Hammar lake and the third between the Hilla canal and the Euphrates.

Reeds and bushes thickly cover the banks and shallow portions of the marshes. These provide an excellent nestling grounds for migrating birds in winter. The main crops grown on the marsh borders are rice, millet and, in winter tomatoes, while animal husbandry is restricted to raising buffaloes.

This region has a very important economic role. It provides the country with large agricultural areas and with sites for its large cities like Baghdad, Basra and many others. The level land is easily titled and it yields abundant crops. It may be that agriculture has been carried on here longer than any where else on earth . in addition to the above mentioned crops, wheat , barley, cotton, corn, sugar cane, fruit and vegetables are produced in large quantities. The Shatt-al-Arab is the largest date-palm area in the world. Dairying and poultry farms are widely spread.

Minerals are also found. Oil fields in Basra and Misan are among the major oil fields in the world. Oil, natural gas, salt, limestones, sand and clay are row materials for many flourishing industries in the region.

Inland lakes, such as Al-Habbaniya on the Euphrates constitute a fine holiday resort ideal for swimming, fishing, boat-racing and sunbathing. Marshlands such as Al-Hammar, Huwaiza and Sanaya attract many tourists. Environmental pecularities as well as sunny and warm weather in winter encourage large numbers of people to go boating, fishing and duc hunting. It was on the marigins of these marsh lands that human history began.

Everywhere you go in this region there are traces of achievement of ancient civilizations. Every historical period has its own characteristics and its own geographical distribution. It is a cultural mosaic nicely arranged from the southern part of the plain, where Sumerian civilization flourished, to the Babylonian civilization in centre and a widely Arab-Islamic heritage spread in between.

These have become cultural centres visited all the years round.

The Western Plateau (Deserts)

This is the largest physiographic region in the country. It occupies and area of 171,817 square Km, or about 39.2% of Iraq total area. The surface rises gradually from 400 feet in the east to 2,000 feet in the west. While rock formations change to be of a younger geological period as one goes from west to east. Surface drainage takes a west-east direction in general, but manty streams bring large amounts of water from Sinjar mountain to be drained southward to the Wadi Tharthar, the largets depression in Iraq. since 1956, it has been used to store excess Tigris water diverted near the Samarra Barrage. It was lately connected with the Euphrates and the Tigris by two feeding canals to divert enough irrigation water back to the rivers.

Within this very extensive region, there is a number of different plains; al-Widian (valleys), Jezira (island), al-Hijara (rock), al-Hamad and Dibdibba. The differences are based on physical factors such as relief and rock formations. A brief informative discussion of each may be useful to comprehend the whole picture.

The Widian Plain, developed in an area of limestone and gypsum rock level to undulating with shallow to rather deep valleys which have a dendirtic pattern. In the northern Widian area is the large Ga'ara depression north of Rutba.

The Jezira is what has remained of an old inlandsea. It a dissected up land area across which the rivers flowing in a well-developed valley. At present it is a large desert and steppe area. In winter and spring, especially after a good rainy season, the northern portion is covered by desert grasses which provide grazing land for camel sand sheep. There are many saline lakes, marshes and depressions. Wadi Tharthar is the largest one.

Al-Hijara is a flat, stony plain with some shallow valleys.

Al-Hamad plain is at the extreme western corner of the country. It developed on limestone rock formations. The plain is nearly level and featureless.

Dibdibba plain occupies the southern portion of this region west of Basra. It developed on sand and gravel and the surface varies from level to slightly rolling land. amid such a flat plain Sanam mountain rises to 300 feet. It is some sort of a lacolithis dome with a limited area. Tamarask bushes are planted for different purposes.

Landforms of wrappings, foldings and faults are found throughout the region. Al-Ga'ara and Assalman basins occupy eroded domes, while geomorphic arid landforms are found in many localities. Buttes and mesas are characteristics of isolated remnants of hard resistant limestone. Sand dunes 30 metres high m, as well as low Burkhan ones, are typical desert features. Caves, dry underground channels and springs are hard topographis phenomena associated with limestone area, Water-springs in Ain al-Tamur and bituman and sulphorated briane springs near Hit.

At present the region has seen considerable changes. Since the 17-30 1986 Revolution a crash development programme has been put to work. Speedy high ways and new rail way line cris-cross the region. Dams have been build across a number of valleys such ah Houran, to store large quantitities of water flowing after heavy torential rains.

Phosphate deposits are commercially mined and exported. Sands are used in the glass industry. Many edxperimental farms and new settelemnet have been build. Water covered areas the region, like al-Habbaniya and Tharthar, are surrounded by well developed recreations centres. All in all, the region has become an active national area.

Rivers and Lakes

Water resources in Iraq are controlled by the twin rivers, the Tigris and the Euphrates. Both rivers have their headwaters in the humid mountains of Turkey where much of the precipitation falls as snow, and both are subject to wide seasonal fluctuation.

In the rolling areas, the rivers flow in well-defined valleys so that irrigation is normally limitto their flood plains. As soon as they enter the depositional plain they become meandering rivers. The Euphrates enters the plain near Hit and becomes irregular south of Hindiya, while the Tigris' entrance is at Balad and becomes irregular south of Kut.

South of these entrance points the rivers flow with a gentle gradient and their currents are unable to move the sediment brought down from the hills, deposition follows, and natural levers are developed. Here the Tigris and Euphrates flow on lever ridges above the level of their extensive floods plains, thus making possible the extensive network of canals which in ancient times converted into the Garden of Eden, and which in modern times have made this the greatest date-producing region in the world.

Rivers in arid regional lose water by seepage, evaporation and diversion for irrigation. This is notably true with Tigris and Euphrates, the law-water discharge of the Tigris past Baghdad amount to 158 cubic metres per second. The mean flow is 1236, and in flood it rises to 13,000. So much water is lost down-river that near the junction with the Euphrates the corresponding figures are 11,78 and 179 cubic metres. These figures may have changed due to many river controlling and irrigation schemes, which have been done lately, but the discharge pattern still holds true. At their southern ends both rivers enter vast marshlands areas. To have a more comprehensive picture of each river some details are required.

The Euphrates

The Euphrates has an over-all length of 2,900 kilometres, and a drainage basin of 289,300 square kilometres. It rises in the rugged high humid mountains of eastern Turkey. Before it enters the Arab land in Syria near Tarabulus, the river already has flown for 440 kilometres through Turkey. In Syria the river flows 675 kilometres in a level and arid land, where it meets its main tributaries, the Blaikh and Khabour.

The Euphrates enters Iraqi territories at Husaiba village to start a long 1015 kilometres journey in a south-east direction. Cutting its way through the western plateau, the river flows in a broad, shallow and well-defined valley passing rapids and cataracts in many places. Islands amid its channel are not uncommon. Passing Hit the river starts to flow through its gradational plain. To the south-west of Ramadi, 36 kilometres south of Hit, is Habbaniya lake. It is a natural retention basin with a good storage capacity. Engineering works, now diverts surplus flow into this reservoir and reduce the likelihood of serious flood. It has a maximum surface area of 426 square kilometres and a storage capacity of 3.4 billion cubic metres. Any extra amount could be discharged to Abu Dibis depression south of it.

In the northern part of the depositional plain the topographical position of the Euphrates is somewhat higher than of the Tigris. Due to this fact the land northwest and southwest of Baghdad, that is north of Falluja and Hindiya, is irrigated by the Euphrates water. Near Faluja the river becomes 40 kilometers away from the Tigris. At Hindiya the Euphrates branches off into two rivers, Hilla and Hindiya. After a short distance they meet again to form a single channel north of Samawa. Still flowing in a southeast direction, the Euphrates passes through Nassiriya and Suq-ash-shuyukh before it enters Hammar Lake. There it flows in undefined channel til it joins the Tigris at Garmat Ali north of Basra.

Recent engineering work has given the river a new appearance and a different flow region. Seven kilometres north of Haditha, ''Al-Qadissiya Dam'', 8150 meters long and 54 meters high, has been recently completed across the river. A long lake will extend in front, and the variable discharge region of the river will be well under control.

The Tigris

The Tigris measures 1970 kilometers and has a drainage basin 19,000 square kilometers. It rises at the humid mountains of southeast turkey. The river at the upper course has a number of small creeks. A single channel formed after an eastern tributary, the Tigris, and western one, Botan Sou, meet together. Flowing in a south-eastern direction, the river passes through rugged Turkish areas for 300 kilometers. Within Iraqi national territory, the Tigris (measured at 1,290 kilometers) first passes through the border village Fiesh Khabour. Then it passes through Fatha which separates Hamrin and Makhool uplands. Within this area the Tigris flows in a well-defined stony banks and a narrow flood plain. This picture can be seen north of Samarra. Starting from Balad the river flows in a featureless depositional plain. Associated with a gentle gradient, meandres are numerous notably in the area between Baghdad and Kut.

Above Kut barrage the Tigris branches off to Garraf and Dujailah canals. Form both sides, five more canals branch off at Amara namely, Misharah and Kahlaaon the left and Bitairah, Mijar Al-Kabir and Mijar Al-Saghir on the right. Due to this fact, the Tigris channel becomes very narrow and the volume of its water is very limited. South of Uzair, with increasing amount of water running back to the river from the surrounding marshlands, the channels widens again till it joins the Euphrates at Garmat Ali.

The Tigris level is usually high in April and May and law in September and October. This shows a little difference from that of the Euphrates where the level is high in April and has its maximum in May. The minimum is usually in September and October. Another significant difference is that the Tigris receives an additional amount of water from a number of tributaries within Iraqi national territory. These are:

a) Khabour which rises in the Turkish highlands and joins the tigris at Fiesh Khabour.

b) Zab Kabir (Greater Zab ) rises in the Turkish highlands nad joins the ancient historical city of Namrood. This is the main tributary in terms of the volume of water. It has been estimated that 33 per cent of the water that flows in the trunk river is brought by Zab Kabir.

c) Zab Zaghir ( Lesser Zab) rises in the eastern highlands outside the country and joins the Tigris south of Sherqat.

d) Adhaim: the headwaters are entirely within Iraqi national territory. It joins the Tigris at Balad. Adhaim is a seasonal river. Winter rains bring large mountains of water heavily loaded with sediments, but it is merely a dry channel in summer.

e) Diyala: the headwaters are partly within Iraqi eastern highlands, and it joins the Tigris a short distance should of Baghdad.

Like the Euphrates, the Tigris has its own flood retention basin with a very large storage capacity. By way of Samarra barrage the Tigris floodwater can be diverted to a structural basin, namelt al-Tharthar. The maximum storage capacity of the depression is 85 billion cubic meters. It is the largest man-made reservior in the world next to Nasir Lake in Egypt. Upstream dams, across the Tigris and the tributaries, also hold back water for irrigation. The latest to be erected across the Tigris is a 3,500 meters long and 126 meters high ‘’ Saddam Dam’’ near Mosul. Others are Derbandikhan and Hamrin dams on Diyala and Dokan Dam on the Lesser Zab. More dams are planned such as Bakhma on the Greater Zab and Adhaim dam. All will be multiple purpose dams.

To the length of he twin rivers must be added 190 kilometres for the Shatt-al-Arab formed by their junction. This is to place the Shatt-al-Arab system among the 16 longest rivers in the world. Karun, which flows from the east, is the only tributary. With a depth of 32 feet, oceanic ships can move upstream to a distance of 80 kilometres away from its outlet at the Arab Gulf.

Iraq is the largest date-producing country in the world. Eighteen million of its 30 million trees grow along the Shatt-al-Arab where the tidal rise and fall of the lower river send surge of fresh water into the canals which properly irrigate the date groves.

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