Iraq has a unique irrigation system since the early history, these systems are functioning through many irrigation projects built over `Tigris and Euphrates Rivers. Irrigation projects include several categories, which are dams, barrages, canals, drains, pumping stations, regulators, and reservoirs. There are six large dams inside Iraq, 5 are existing in Tigris basin, and one in Euphrates basin, these dams which were built since 1950’s are suffering from several issues, like foundation liquefaction, seismic effects, and others. Tharthar Lake, Habbaniyah Lake, Razzaza Lake, and Southern Marshes are also one of the main projects in Iraq to control flood and storing excess water in some. These lakes serve in protection of the main cities during large floods. There are also many barrages on Tigris and Euphrates, some of these barrages are part of Tharthar and Habbaniyah projects, while others serving the irrigation projects in Mesopotamia. On Euphrates, there are several irrigation projects, where the projects upstream Fallujah city are almost small or medium projects irrigated by pumping. Then, in the rest of Euphrates, there are Great Abu Ghraib project, Great Mussayab, Hilla-Kifil, some small projects, and Kifil-Shinafiyah projects. Also, Hilla branch which is the largest branch in Iraq from Euphrates, where this branch is irrigating several irrigation projects. On Tigris basin, there are Jazeera project irrigated by pumping from Mosul Dam, Kirkuk project that is irrigated from Lesser Zab River, and Diyala are projects. Inside Mesopotamia and over Tigris reach, there are Ishaqi project, Nahrawan project, Middle Tigris projects, Dujailah project, Dalmaj project, and Gharraf Canal projects. In the middle of Mesopotamian plain, Main Outfall Drain was completed in 1992, this grand drain are serving around 6 million donum of farmlands.

Mesopotamia is a land where floods have occurred very frequently. Many destructive floods had been registered by historians, who noted also the food control schemes used in those times. Over history, many structures were built and managed, but this work was taken up again by the General Directorate of Irrigation which was formed in 1917 to manage floods and reduce as much as possible losses, in addition to the development of irrigation works. Plans were made to build a sophisticated flood control and protection system. Several projects were proposed, and since the 1950s they were successfully implemented. Many multipurpose dams were built to mitigate flood conditions in addition to their other functions, such as Mosul Dam, Dokan Dam, Derbendikhan Dam and Haditha Dam. Other projects which were solely planned for flood protection include developing and using natural depressions such as Habbaniyah Lake on the Euphrates River and Tharthar Lake on the Tigris River, to protect Mesopotamia from floods. Moreover, the southern marshes in lower Mesopotamia may be utilized for flood protection. This paper deals only with these natural depressions leaving the dams at the time being.

Euphrates River is one of the two rivers where the civilization and irrigation had started, many major irrigation systems are still operating for centuries. The most important advancement of irrigation within this area happened after 1920s, where new structures were constructed, new canals excavated, new pumps installed, and salt affected lands were reclaimed. The major irrigation projects in along the reach of Euphrates within Mesopotamia are, Great Abu Ghraib, Great Musayab, Hilla Branch projects, Kifl-Shiniafiyah, in addition to many other medium and small size projects. Besides, some important Barrages have been built for controlling water levels of the Euphrates for proper operation, such as Fallujah and Hindiya Barrages. There is a great need for more reclamation in the lower parts of this territory, as well alternatives are needed to avoid discharging saline drainage water to the Euphrates in some projects.

Several irrigation systems have been built at Tigris River basin within Mesopotamia plain. The upper part of Tigris at Mesopotamia is extensively exploited, and several major projects were constructed since the 1970s. These are Ishaqi, Khalis, Diyala Combined Reach, Nahrawan, Dujailya and Dalmaj. Other projects were partially developed, which are Middle-Tigris, Gharraf projects, Great Amarah and KutButaira. The important barrages in this part are Kut Barrage, as well, as the barrages in Amarah area which are of vital importance for irrigation and navigation. Shaat Al-Arab is one of the most important waterways in Iraq. This river has been suffered from water scarcity and riparian countries actions. Solutions for adaptation to adapt the situation were studied and planned carefully, but still there is need for more work to cope with the situation in Basra area.

Since early civilization and the farmers in Mesopotamia are suffering from the soil salinity. This problem had caused the transfer of power from the Sumerians to the Babylonians in ancient history. Great efforts and research have been made since the beginning of the 20th century to overcome this salinity problem. Experts have concluded that the main reason for salinity is the salt content of irrigation water and the shallow saline groundwater derived from the irrigation activities. General schemes were planned, which involve building a new system of drains in parallel to the irrigation network. The backbone of the drainage system in Mesopotamia is the Main Outfall Drain (MOD). Large works such as Musayab Main Drain, Main Outfall Drain, Great Gharraf Drain, East Euphrates Drain were implemented, but there are still large needs for much more work to be done.

Water harvesting in Iraq is an old application with limited extent. Western Desert, Jazeera Desert and Eastern Valleys, are the zones were the water harvesting must be employed. Several water harvesting dams in Western Desert had built since 1970s, these dams are intended to provide habitat and recharge of groundwater resources. There is limited opportunity to recharge groundwater in Jazeera area due to existence of gypsum layers. Regarding Eastern Valleys, the experience of building water harvesting dams on the valleys manifested that sediments accumulation is the main obstacle to adapt this solution. Hemrin Hills considered as one of the most intensively eroded areas in Iraq, so, soil conservation and water harvesting development is important. Many small dams were built in mountainous zone in the last two decades, some are important for agriculture expansion, but there is need to evaluate the effects on large dams feeding. North-Eastern parts of Jordan, which has similar natural conditions of Northern Desert, had present a successful example of water harvesting development.  

Barrages are the early water resources structures that were built in the modern history in Iraq. The main function of the barrages to rise the water levels to feed the main canals of irrigation projects. Further, some barrages are functioning as a diversion structures during floods. The first built barrage and still in operation is Kut Barrage which opened in 1939, while the last one is Amarah Barrage that were opened in 2004. Some of the barrages are in good conditions, some are suffering from technical issues, and others especially at the lower reaches of Tigris and Euphrates Rivers getting insufficient maintenance. Generally, the upstream approaches need dredging of the sediments and small islands, and there is a need also for bathymetric survey of the rivers sections near barrages.  

Euphrates River is distinguished with long existing irrigation projects, which had been developed in the 20th century after centuries of deterioration. One of the major projects a long Euphrates inside Iraq is Great Abu Ghraib Project, which is the largest reclaimed area. Also, Great Musayab Project, Kifl-Shinafiyah Project and Shinafiyah-Nasiriya Project are other major projects. The most important for which Hindiyah Barrage had been built is Hilla Branch that supply many projects on both sides of this branch. Euphrates irrigation projects need a lot of investments to develop the status of the projects and confront the continuous decrease in water quality of the river. 

Along Tigris River reach inside Iraq, many large and small projects of irrigation were built. These projects depend on gravity flow or pumping. Starting from Jazeera project then small projects downstream Fatah, where these feed by pumping. After Samarra scheme, the important Ishaqi project, then after Baghdad, the projects of Nahrawan, Middle-Tigris and Dalmaj. The most important branch from Tigris is Gharraf Canal, which is not exploited yet, although plans were prepared decades ago. Downstream Kut Barrage, several projects are especially on the right side of Tigris. Finally, Shatt Al-Arab project which has a unique importance as it provide the solution for municipal need and save the orchards of dates in Basra.  

There are five tributaries feeding Tigris River inside Iraq, on these many large and small projects were developed. Two kinds of projects can be distinguished, first the projects of complementary irrigation or semi-rain feed area for agriculture, and example of these projects is Kirkuk, Hawija, Eski-Kalak and small projects in mountainous area. The second group is the projects that depend mainly on irrigation, examples of that are the projects in lower Diyaa. Unfortunately, there was no exploitation of lands enough comparing with the available resources in Great Zab territories.

Iraq has a unique system of drainage. Soil texture, groundwater depth, water quality and other factors lead to the adaption of getting rid the drainage water away to the sea in order to control water quality. The system of drainage is not completed yet, however, the backbone of the system, which is Main Outfall Drain (MOD) was completed in 1992. Other main drains were completed and connected and others are still in progress of implementation where the most important drain after MOD is Eastern Euphrates Drain.

Many medium and small dams were built in Iraq. These dams are distributed in three major areas. First is the northern area where many dams built in the period after 2003, even there are some that built in 1980s. Second, is the dams built in the eastern valleys, but these prove to be inefficient due to high rate of sedimentation even in the live storage. Third, is the dams in the western desert. These dams were  highly exploited in 1970s and 1980s to harvest as much as possible in this large and promising area and providing the livelihood conditions to settle people. The area has no more projects due to security issues.

Iraq had suffered for centuries from devastating floods, causing heavy life and property losses and for occasions it demolished the civilizations. Since 1950s, Iraq started to develop several natural depressions to function as escape to mitigate flood waves. The projects of this kind which had developed are: Habbaniyah project, Tharthar project, Schweicha depression and Southern Marshes. The exploitation of these projects comprises building barrages, regulators, and dykes. For Tharthar and Habbaniyah, the diverted water re-used during drought season. Although, these depressions which serve as reservoirs provide invaluable role in flood protection, the construction of the existing and future dams will reduce the feasibility of these projects.

Several dams were built on Tigris, Euphrates, and Tigris tributaries in Iraq. The construction of dams had been done in the second half of 20th century. Of the most critical issues confronting the large storage dams in Iraq are the liquefactions in Mosul Dam foundations, land sliding and earthquake effects in Darbandikhan Dam, and the essential maintenance and rehabilitation requirements almost for all the dams. Absolutely, large storage dams made Iraq surviving from thirst in several occasions. Unfortunately, after 2003, the attention or will are not exist pertaining the building of new or partially built large dams.      

Reclamation in Iraq was known in 1950s, where the problems salinity and water-logging are mainly apparent in the middle and south of Iraq. The early interventions in reclamation sectors was simple, not precise, or calibrated properly, hence, salinization and water-logging aggravated. Since the reclamation activities are time and resources consuming, which may last in several years, these are highlighting the fact that most of the beneficiaries could not afford the conducting of this activity. Therefore, Iraqi government take the decision in 1970s to carry out the reclamation and improve the agricultural processes vertically. There are millions of donums were reclaimed along Iraq. There are key steps adopted to conduct the sophisticated reclamation in order to get rid of salinity, lowering water table to acceptable depths, and prevent future salinization. The reclamation is not just an engineering project, the full reclamation are also may include, rural development, capacities building for operators and beneficiaries, educational development, research development, and social development.

As time progressed Iraq witnessed the transfer of power from the hands of the Umayyad dynasty in Syria to the Abbasids who established their State in Iraq. The following developments are detailed. During these days very little had happened with respect to land ownership, the question of Kharaj tax and even the agrarian relations between property owners, private farmers and the general peasantry. It may be assumed therefore, that at the start of the Abbasids period all the irrigation networks and infra structures were in good working conditions, and that all the required work force was available as the case had been in the Sassanid and Umayyad periods. The Abbasids may be credited for keeping the vast canal network of al-Sawad in good working conditions and they knew well that the major source of their revenue came from agriculture. Full description of the major canals, which had supplied the lands between the Tigris and Euphrates Rivers. The five  main canals or arteries were all fed from the Euphrates and flowed in south easterly direction towards the Tigris where they poured;  so naturally they were used for navigation between the two rivers in addition to irrigating all the lands  here by vast networks of distributaries and branch canals and watercourses. The major part of these systems was inherited from the Sassanids and the Babylonians but they were kept in good working conditions all these centuries by good management and maintenance. These five major canals according to their sequence from upstream to downstream were called during the Islamic era as, Nahr al-Dujail off taking from the Euphrates at a short distance above Anbar, followed by Nahr Isa, Nahr Sarsar, Nahr al- Malik, and finally Nahr Kutha. The Euphrates River itself bifurcated at its downstream reach to two branches whereby its eastern branch irrigated in its turn a very extensive tract of land in the southern part of al- Sawad with a complex system of branches and tributaries. In following each of these canals great deal of details are given on the agriculture of the various districts and the towns they had served, their  flourishing conditions and the prosperity they  had enjoyed. Khalifah al- Mansour built the new capital of the Abbasid State, Baghdad at the heart of the Sawad region. There was a vast system of watercourses which served Baghdad and its environ that had originated mostly from Nahr Isa is also treated not failing at the same time to describe even the minute details of the various quarters of the city and the markets they had served, which were all based on the writings of contemporary Scholars. The long and deep trench called as the Shabour Trench, which had extended from Hit on the Euphrates down to nearly the Persian Gulf was given its share of detailing as it stood some waterworks, which was meant for defense rather than irrigation. This stream was carrying the major share of flow of the Euphrates during the Abbasids period before it ended indirectly into the Batyiha. It gave however very large branch from its right hand side before reaching the site of Babylon which was called Nahr Nil. This important canal flowed in southeasterly direction and poured at the end in the Tigris in the same fashion as the previous canals did and similarly spreading irrigation watercourses all the way down.  

The new rise of Babylon is reported and its domination of the old world is described; when two dynasties ruled Neo- Babylonia from 612 BC to 330 BC.  First, the Chaldeans had taken over from the Assyrians whom they had defeated and established their empire, which lasted for 77 years followed by the Achaemenid dynasty, which was to rule Babylonia for the remaining period as part of their empire. Out of the 77 years of the Chaldean period king, Nebuchadnezzar II ruled for 43 years, which were full of military achievements and construction works and organization. Apart from extending the borders of the empire, he had managed to construct large-scale hydraulic works which were intended for irrigation, navigation and even for defensive purposes. He excavated, re-excavated, and maintained four large feeder canals taking off from the Euphrates, which served the agriculture in the whole area between the Euphrates and the Tigris in the middle and lower Euphrates regions. Moreover, he was concerned with flood protection and so he constructed one large reservoir near Sippar at 60 km north of Babylon to be filled by the Euphrates excess water during floods and to be returned back to the river during low flow season in summer. His works involved river training projects, so he trained the Euphrates by digging artificial meanders to reduce the velocity of the flow and improving navigation and allow the construction of the canal intakes in a less turbulent flows. It seems also that he had diverted the river during the building of Babylon Bridge and trained the Euphrates River penetrating Babylon by constructing riverside revetments. Nebuchadnezzar II had the foresight for building extensive defensive fortifications to secure the country against possible enemy attacks from the north and adding to the walls and fortifications deep moats filled with water for higher security. This was the case with the wall he built north of Sippar. It extended over the whole distance between the two rivers, and the wall around Sippar itself. Similarly, he had dug a great moat alongside the wall of Babylon, which he supplied with water from the Euphrates. Moreover, he had introduced improvements on the four large feeder canals and the extensive canal networks that belonged to them to be used as water barriers against the advance of any enemy troops. Building temples and grand royal palaces and the Babylon Bridge took part of Nebuchadnezzar’s attention and his name was linked with the “Babylon Hanging Gardens”, one of the seven wonders of the ancient world, which he had built to please his wife. Description of the gardens according to historians is given in this book in addition to reporting the results of archeological digging of the supposed site, which can shed light on the irrigation method used to irrigate these elevated gardens. The flourishing agriculture and wealth and prosperity it had brought to Babylon during Nebuchadnezzar’s reign is described in details, and the active trading and commercial dealing it had generated is also treated. The first banking services in history related to this period, which was linked to one Jewish family known as “House of Êigibi” is described. This family continued to serve for very long time by collecting the land rents and water taxes for canals use for the government, in addition to concluding contracts and ratifying transactions for the public. As bankers, they gave farmers loans to invest in all types of agrarian operations and practiced money transfers between various cities which helped trading especially with large scale export and imports of the various crops. The Chaldeans rule of Babylon came to an end in 539 BC when Babylon fell to the Achaemenids attacks that were already established in Persia led by Cyrus II. Babylon, however, kept a special position between the various capitols of this empire due to its splendor and wealth. It served therefore as the economical capitol and the winter residence of the kings Achaemenid Empire for most of this period while its agriculture continued to generate a great portion of the empire’s revenue. The archive gave us information on the agrarian relations and the agricultural outputs in Babylonia at that period. During the Achaemenid times, as it was the case during the Chaldean times, irrigation systems in Babylonia were kept under close observation and good maintenance which kept agriculture at its best. The inevitable decline of this empire came in the end due to the rule of weak kings, conspiracies and palace intrigues, and finally the bitter defeat came on the hands of Alexander the Great who entered Babylon in 331 BC and kept it as the Jewel of his new empire.

In more than six centuries which followed the fall of Baghdad to the hands of Hulagu and his Mongol troops in 1258 until the establishment of the modern state of Iraq in 1920. The timeline of the country cannot be described but only as a sequence of tragic events in which this once most prosperous land sank into unending bloodsheds, destruction, constant retrogression and deep poverty. Calamities such as flooding, epidemics, locusts and famines did not spare millions of its population, and to speak of Baghdad only, the 1,000,000 who used to live there in the golden days of the Abbasids dwindled to merely few thousands at the turn of the twentieth century. The early stage of this severe collapse was due to the interference of the Mongols with the irrigation systems on which the life of people had depended. Admitting that the damage that was sustained during the Buwayhids and Seljuks times left these systems in dilapidated and bad conditions, but the Mongols managed to add more destruction so that agriculture diminished to small plots of lands, which could not keep up the large population anymore and made any effort of reform nearly impossible. Borrowing from the words of Stephen Hemsley longrigg in his book “Four Centuries of Modern Iraq” he says:

“Most ruinous of Holagu’s acts had been the studied destruction of the dykes and head works, whose ancient and perfect system had been the sole source of the wealth. Disordered times, and the very silting and scouring of the rivers once let loose, soon made the restoration  of control the remote, perhaps hopeless problem today still unsolved”^[1].

After two centuries after the fall of the last Sumerian dynasty of Ur in 2003BC, the first kingdom of Babylon did appear. The Amorites who were Semitic people who had lived in the west of middle Mesopotamia brought the collapse of Ur itself. They appeared as nomadic clans ruled by fierce tribal chiefs, who forced themselves into lands where they needed to graze their herds. There was no Amorite invasion of southern Mesopotamia as such, but the Amorites ascended smoothly to power in many places, especially during the reign of the last kings of the Ur III dynasty, and so the following Amorite dynasty took over the rule of long-extant city-states such as Isin, Larsa, Eshnunna, and Kish and also established new ones. After a brief periods of an Elamites and old Assyrian empire dominations that took place for only 46 years the Amorite kingdom was firmly established in 2004 BC in Babylon and continued until 1595 BC, known in Mesopotamia’s history as the "Amorite Period". Babylon became the major power in the ancient world during the reign of Hammurabi. It was from then that all parts of southern Mesopotamia came to be known as Babylonia. It was during the reign Babylonia witnessed the great care he had devoted to maintain and expand irrigation networks and keep the prosperity of the empire and even so successfully constructing new canals and dams. When Hammurabi established control over the whole region of Mesopotamia by 1760, and especially the city-states of Sumeria, he restored the irrigation canals there to their best conditions and brought water back to areas of the south that were previously deprived of it. His unification of the entire south and the lands north of Babylon allowed him to dig long canals to the various cities of these lands. The canal he called “Hammurabi-is-the-abundance-of-the-people”, for example, ran by Nippur, Isin, Uruk, Larsa, Ur, and Eridu, and covered a stretch of land extending for a distance of some 160 kilometers. These works brought economic development and increased the wealth of the population to unprecedented levels. Hammurabi’s achievement as a lawmaker is specifically highlighted; as he was famous for his “Legal Code” which he had promulgated.

The first steps taken by Man in the long journey towards the establishment of the first known settled society. From the end of the last ice age to this, point which had taken 12000 years. The book explains the changes in climate, which made the first appearance of agriculture and the domestication of animals possible after many thousands of years of food collection and hunting for food. The first attempts to build settled communities are explained, which finally were calumniated in the establishment of stable settlements at the south of modern-day Iraq, where irrigated agriculture was practiced for the first time in history on the edges of its southern marshes. The people known as the Ubaid who were attracted to this place by the temperate climate and the rich resources of the land found such settlement as Ur, Eridu and Uruk. These people, explains the book, practiced irrigated agriculture and pottery and it was from archaeological findings of such pottery and the symbols engraved on them that their history became known to us. However, not having any form of writing, explains the book, the reason why historians had placed al- Ubaid people in the prehistory period, as they have not passed to us any documented written history. The beginning of history as defined by historians and ascertained by the author begins only with the invention of writing which was accomplished by the next People to live in this area who were the Sumerians.

Mosul Dam is the second biggest dam in the Middle East due to the capacity of its reservoir. Since the operation of this dam in 1986, it is suffering from seepage problems in the foundation of the dam due to the dissolution of gypsum and anhydrite layers under the foundation. This phenomenon has raised concern about the safety of the dam. Studies done during the recent years showed that grouting works can only be considered as a temporary solution at its best. It is clear now that while grouting must be continued search for long term solution must be sought if dam failure consequences are to be avoided. This must be done as soon as possible as the dam is showing more and more signs of weakness. It is further considered that the suggestions and recommendations forwarded by the team of Lulea University of Technology and the Panel of Experts in the Stockholm Workshop 24-25 May, 2016 give the most practical and suitable solutions for this problem.

Dams are very important infrastructure to any country where they serve for different purposes. Unfortunately, they represent risks to life and property due to their potential to fail and cause catastrophic flooding. Recent studies indicate the possibility of Mosul Dam failure. For this reason different failure models were used to estimate the consequences of such failure. Almost all models applied gave similar results. It is assumed that in case the water level in Mosul Dam reservoir is at its maximum operational level the effected population will reach 6,248,000 (about one million will lose their life) and the inundated area will be 7202 square kilometer. This catastrophe requires prudent emergency evacuation planning to minimize loses.

The idea of building of Mosul Dam project started in 1950 and it was referred to as Aski Mosul Dam. Since that time, number of companies worked on the site selection and design of the dam. All the above companies suggested that the dam should be Earth-fill type with compressed clay core but there were different views about the exact location of the dam, spillway and electricity generating station. Grouting was suggested to be performed under the dam, spillway and the electricity generating station. In addition, they suggested that detailed geological investigation should be performed before any construction activities. In 1978, the Swiss Consultants Consortium was asked to be the consultants for Mosul Dam project. The consultants suggested that the operational water level at the dam to be 330 m (a.s.l.) while the flood and normal water levels to be 338 and 335 m (a.s.l.), respectively. The work started on 25th January, 1981 and finished 24th July, 1986. The foundation of the dam is built on alternating beds of limestone and gysum. Seepages due to the dissolution of gypsum were noticed and after impounding in 1986, new seepage locations were recognized. Grouting operations continued and various studies were conducted to find suitable grout or technique to overcome this problem. The seepage due to the dissolution of gypsum and anhydrite beds raised a big concern about the safety of the dam and its possible failure. It is believed that grouting will not solve this problem permanently

Writing history is not an easy or simple task. Even historians normally approach it with caution and care to put the events in the correct perspective in time and setting. Trying to read history of a particular historical event and drawing the right conclusions is, however, an even more difficult work. Different motives may lay behind writing the history of a particular event which necessitates looking into it from different angles and trying to reach an unbiased conclusion. When I decided to write on the history of “Irrigation and Agriculture of the Land between the two Rivers” as an engineer, I thought that the problems involved are insurmountable, and maybe I should leave it to others. The challenge was very strong, and finally I decided to take it. The real problem was not in the absence of references, but on the contrary, there were so many of them that they needed to be scrutinized carefully. Archeologists who had dug in hundreds of sites in Iraq were so many, and their writings were so bulky for their work spanned well over hundred and fifty years. Many historians have also produced thousands of pages on the subject. In selecting resources, much weight had to be placed on primary older references whenever available. In all cases, I have listed the websites in which these resources are found; which is in conformity with the present-day intensive use of the internet to allow readers and researchers to refer back to these original sources for more details.

As the history of this land continues to unfold, we come to the time when the capitol of the State was moved to a new city to the north of Baghdad, which was called Samarra, and this was the opportunity taken by the Khalifahs to build new palaces and excavate new canals and open more land for cultivation. In this paper details on the building of Sammara by Khalifah al- Mu’tasim, son of Khalifah Harun al- Rashid and moving the capitol to it from Baghdad in the year 836 and remaining as such until 892 are given. One of the main reasons which led al-Muʿtaṣim to build Samarra and moving to it was the problems raised by the presence of his Turkish slave-soldiers in Baghdad and the friction they had created with the population. Al-Muʿtaṣim construction works in Samarra, the various public buildings, and numerous palaces he constructed here are described. As the city was located on the eastern bank of the Tigris, water supply could not be drawn to it by gravity since its location was higher than the river and even higher than the Katul Kisrawi canal adjoining to it from the east. Therefore, the irrigation works of al- Muʿtaṣim were concentrated on the western bank of the Tigris, which he had already connected it to the right bank by building a bridge. The main irrigation work he embarked upon was the construction of Nahr Ishaqi Canal. This old canal dated to the Partho- Sassanid era but it had to be re-excavated and remodeled since it was already filled up by sediments and abandoned. More over the canal had to be extended for a very long distance downstream to irrigate all the qati’as he had given to his top generals and courtiers to develop into cultivations and farms. These farms then produced all sorts of crops and fruits while the large date palm orchards planted here gave the best types of dates. Moreover, the canal in its downward route supplied water to the large tract of land that al- Mu’tasim had reserved for the encampment of his Maghariba troops which was called “Istablat”. Details of the barracks, housing quarters, stables and training arena of the encampment are presented in addition to the three branch canals off taking from Nahr Ishaqi, which were to irrigate also the extensive pastureland that was reserved for the 140,000 cavalry horses to graze in. The canal was then followed to its end in the other old canal called al- Dujail canal. The works of al- Mu’tasim, however, were no match to what his grandson al- Mutawakkil had done which are described. This Khalifah was determined to irrigate Samarra by gravity from the Tigris and to have plentiful water supply to the city and to his palaces and to his many artificial ponds. He embarked on a daring project by constructing a dual kariz and open channel conduit system taking water from the Tigris at a location forty kilometers north of Samarra and running for great part of its length along the Katul Kisrawi canal adapting to the hilly topography of the land. The scheme was then described following its course after crossing the Katul by an aqueduct to an earth reservoir. This reservoir was built to retain the incoming water before distributing it to the main city dual Kariz, and to the canal supplying the Dakka palace. In addition to the flood escape channel that was known as the Nahr Murayr which took off from the west side of the reservoir and passed down to the Tigris where it poured. The main city Kariz system is followed i and the details of its branching network are fully described. Such details covered the water supply to the racing courses, the Dar Khilafa palace and its unique pools intended for the Khalifah’s pleasure and the water supply to Abu Dulaf Mosque congregational mosque with its famous fountain. Having finished in the Tigris at al- Matira this stream could not irrigate the 5000 hectares of land of al- Hayr, or the wild animal reserve created by al- Mutawakkil to practice his hobby of hunting, as this land was above its course. The al- Hayr was so important to al- Mutawakkil that he excavated a new canal directly from the Katul, which commanded the whole area, called it Nahr al Nyzak and gave from its final reach a branch to another palace he built there and supplied one more of his favorite ponds adjoined to it. The construction works of al- Mutawakkil were not confined to Samarra but he extended this to build a new city 18 kilometers to the north of Samarra and called it al- Mutawakkiliyya, and here he again built new government compound, a mosque and gave qati’as to his sons, generals and may more people to build houses and palaces. He built for himself another palace and called it al Ja’fari. To supply the new city with water, he ordered the excavation of a new canal, which he called Nahr al Ja’fari. The intake of this canal was on the Tigris River some forty kilometer north of Tikrit and it followed a course parallel to the river for a considerable distance before it crossed the Katul Kisrawi by an aqueduct and then entered the city. This project proved an engineering failure as the ground, which had to be dug, was extremely hard and the work had to be stopped after spending twenty five million dirham. While some of these works may be considered as grand works, they were very costly and deprived public works such as irrigation networks from their share necessary for their maintenance and proper functioning. This extravagance coupled with political intrigues led to the assassination of al- Mutawakkil in a plot that was planned by his own son. This point marked the beginning of the decline of al- Khilafa which took some more time till it finally collapsed in 1258 fall of Baghdad on the hands of the Mongols. In addition to Samarra and its irrigation work described also the Nahr Dujail canal flowing on the western bank of the Tigris not far downstream from Samarra. Much older than Samarra itself, it was irrigating a large tract of land extending to Baghdad. In description of the course of the canal followed its western branch, which had gone out of use at the Abbasid times and also concentrated attention on the eastern branch that was known as Nahr Batatiya. It irrigated the Tusuj of Maskin before it reached the northern parts of Baghdad and branched into a dense network of watercourses that supplied al- Harbbiyyah quarter. Further details are presented of the various places and parts of this quarter that benefited from these watercourses before the full supply was exhausted. The details as given augment therefore the description of the canal networks serving Baghdad (the round city and the Karkh districts) that had originated from Nahr Isa. The Abbasid Khilafa after it had experienced its golden era began after the assassination of al- Mutawakkil, a long process of slow but steady decline due to multiplicity of reasons.

The irrigation of the Sawad lands which depended on the Tigris River are presented as the subject of this paper. In this paper one of the largest irrigation systems, not only of the old world but even today is described; this is the Nahrawn Canal System which irrigated the whole alluvial lands east of the Tigris extending as far east as the foothills of Persia and from Al- Dur above Samarra towards the south for almost 300 kilometers. From the archeological findings and historical writings, we know that this system had existed for thousands of years. The construction of the old Nimrud dam on the River Tigris was associated with the excavation and construction of this canal, and they were both attributed to the days of Hammurabi the famous king of the Chaldeans which had been mentioned previously although the canal may have been excavated in many stages and by successive kings. The canal and its whole systems were kept in good operational conditions by the successive empires who ruled the country as agriculture in this vast area of land had depended entirely on its water supply. The revenue drawn from this agriculture was a major part of the income of these empires which had fueled their progress, prosperity and their wars. Full description is given of the canal itself and the two feeder canals which had supplied it with water from the Tigris south of Sammara. The third feeder excavated by Khusraw Anushirwan which took off from al- Dur north of Tikrit which was called Katul Kisrawi is also described. More canals which were associated with the Nahrawn Canal such as al- Qawrach and Nahr abu el- Jund are detailed with the circumstances that led to their construction. The trunk canal course and the two massive gravity dams, which served as diversion structures on the Adhaim and Diyala Rivers are described, which were obstructing the passage of the course of the canal. Maps and sketches also supported these descriptions. The towns and settlements along the course of al-Nahrawn Canal are detailed with descriptions based on the writings of the Muslim geographers of the Abbasid period who had reported in length about the canal and the state of the country it had served. The canal was also the main source of water supply to the eastern quarters of Baghdad, which had stretched over considerable area during the days of Khalifah al- Mansour and the following Khalifahs. The distributaries of the Nahrawn, which served the eastern quarters of city on the right side of the Tigris, are, therefore, described in details and the dense network of the secondary canals and watercourses branching from them to serve the various quarters of the city are given full attention. In addition to this, the notes and sketches that were made by two British travelers who travelled along the whole course of the canal in three separate occasions at the end of the nineteenth century are documented with their remarks and notes. In addition, the comments of Sir William Willcocks, the famous irrigation British engineer of the same period, are also added. In summary, the story of one of the greatest engineering achievements of the old people of Iraq in addition to narrating the events that led to its decline and final collapse during the last period of the Abbasid Khalifah.

Declining stage of the Abbasid Khilafa is followed meticulously until its collapse in the fall of Baghdad to the Mongols in 1258. The full sequence of events, which had resulted in this most important event to Mesopotamia is followed and the decline in agriculture in the whole of al- Sawad during this is period, is carefully described. Agriculture had formed the main contributor to the economy and strength of the Khilafa State, but it had continuously suffered neglect and destruction during this period due to negligence of the central governments of the irrigation systems and the destruction of these systems during conflicts and revolts that became dominant during the last phase of al- Khilafa State. The large spending of the late Khalifahs and the depletion of the treasury, and their dependence on foreign military troops, who were mainly Turks, to support their rule, mark the beginning. By loss of sizable revenues, this had interacted again with the Khalifahs weakness causing more revolts and anarchy by various unsatisfied groups and by the troops themselves over their unpaid salaries. The war between al-Muntasir and his brother al- Mu’tazz over the thrown following the assassination of their father al-Mutawakkil is detailed by giving full attention to the large damages it caused to irrigation canals and flooding of large areas between Baghdad and Samarra. Following this the revolt of Zanj in Southern al- Sawad and the long conflict with the Qarmatians are then outlined by reporting the reasons and describing the consequences of those important wars in details, accounting at the same time the high costs of these wars and the extent of severe damages to population centres, cultivation lands and their irrigation works. During the Buwayhids period, the Abbasid Khlilafa experienced its worst moments as the Buwayhids did not contribute much to the welfare of the people, nor could they do much to reverse the trend of decline that was progressing. As a matter of fact they had committed their biggest mistake in tearing apart the land ownership system prevailing till that time by introducing a new form of Iqta’ known as the Military Iqta’s. New methods of land and crops tax collection system were introduced and thus disrupting long established procedures that were followed since the Sassanid era and had proved their success. Conflicts and wars during the Buwayhid rule and the large-scale corruption, which are fully reported here, had undermined the central power needed for the proper management of agriculture and for the well keep of the irrigation canal systems. Finally, when the Buwayhid strength was drained they were expelled under a new rising power in the Seljuks. The Seljuks proved during this period to be not much different from the Buwayhids and their Sultans kept the real power in their hands making the Khalifah a titular head of state only. The conditions of the economy was as bad as it was before, and the people complained much over the recurrent crises of extremely high food prices during these times. Worst of all the Seljuk Sultans surpassed the Buwayhids in practicing the Iqta’ of the cultivated land by distributing qati’as not only to the military leaders as the Buwayhids did but they extend this to an unprecedented levels for the Seljuk Sultans had granted all the land to their Seljuk soldiers, their relatives and friends who were only Seljuks. To comprehend the magnitude of this; the number of the soldiers only in the time of Malik Shah who benefited from this system was forty six thousand horsemen; many more high ranking Seljuk persons were also entitled to qati’as under the same rules. With the passage of time the basic principle of this system were violated, and most of the beneficiaries succeeded in keeping the land as their own , used all sorts of abuses towards their farmers and even passed it in inheritance to their children. Some others encroached on neighboring qati’as, which belonged to others, and injustice and corruption became widespread. Negligence to repair these canals in so many cases leading to the permanent abandonment of land is also cited illustrated with many examples. In addition, many striking cases of failures of canals and their head works after large floods are fully described based on the reports given by contemporary writers. The details presented give an insight to the scale of the large fertile areas and the cities and towns that were badly affected and give evidence to the very low level that the State had reached during its last days after losing so much fertile lands and their agriculture.

The new era after the fall of the Sasanian Empire, which is marked by the Muslims dominion over Iraq, as part of the Islamic Empire. It was only two years after the death of the Prophet Mohammad that the real efforts to spread Islam outside the Arabian Peninsula were made during the reign of the second Khalifah ‘Umar ibn al- Khattab. The Arabs at that time pushed their way forcefully into Iraq, and almost simultaneously into Syria (Bilad al- Sham) and caused the total collapse of the Sassanians Empire and the occupation of large part of the Roman Empire. The Islamic troops that invaded Iraq settled with their families in new towns, which they had built as encampments. Basrah and Kufa were the first of these towns and followed later on by Wasit. The locations of these cities and the further steps taken in their development are described here. Basrah being at some distance from Shatt- al Arab and the Euphrates had no water supply and therefore two large canals, the Ubulla canal and al- Ma’qal canals, which were excavated on the orders of ‘Umar himself, brought water to it. The policy adopted in the following years was to grant the lands around Basrah freely to wealthy Muslim investors who should reclaim these lands and excavate irrigation canals for their cultivation. This was known as the qati’as system of land ownership, which resulted in a boom in agriculture in the area. The treasury had benefitted from the tax imposed on these lands and their yield, which was called (Karaj). The same qati’a system was practiced in Kufa but to lesser extent than around Basrah as most of the land was already cultivated and owned by people who did not resist the Muslims conquest and therefore they were entitled to keep their lands against payment of another type of tax. The only lands that were granted as qati’as were those, which had belonged to the Persian Crown or owned by Persians who had left after the conquest. The lands in this area mostly belonged to the He’rians who had their capitol al- Hira, close to Kufa and their kingdom was a vassal kingdom under the Sassanians. In the other case, of the city of Wasit the third Islamic city to be built in Iraq, established by al Hajjaj. He was the governor of Iraq during the Islamic Umayyad dynasty rule (661- 750). The town he had built was on the right bank of Tigris in the rich district of Kaskar south of Misan .It was renowned for its fertility and good agriculture. Nevertheless its lower part had been flooded by the famous flood of the 629 AD late in the Persian empire timeline in which the Tigris River had abandoned its eastern course (present day course) and ran in a new western course on which Wasit later on was built. The Hajjaj who ruled for 20 years during the Umayyad period therefore had the opportunity of reclaiming large tracts of the land around Wasit and large areas adjacent to the Great Swamp (Batayih) in which he also gave many of the qati’as grants to investors in the same way as was done before in Basrah. Generally, Hajjaj who was very much occupied in quelling revolts and mutinies had also the time to oversee maintenance works of existing canals and dig many more of them.Iraq, during this period and for a long time, which followed, became as wealthy as it used to be during the high time of the Sassanids, and its canal networks functioned well while its fertile and fluvial land supported flourishing agriculture and generated large revenue to the treasury (Bait al- Mall). All the time during the Islamic era until the fall of Baghdad in 1258 AD Iraq was called al- Sawad land, which came from the dark color of the extensive cultivations, farms and lush green orchards of palm trees and fruits as they appeared on the horizon. Al Sawad as defined by the contemporary Muslim scholars extended from Hulwan (Qasir e- Shirin) to Haditha in the north to the tip of the Gulf and Qadisiyya on the edge of the desert in the South.

The Achaemenid Empire collapsed after the failure of King Darius III to stop the sweeping advance of Alexander in Anatolia towards Persia. Therefore, Alexander entered Babylon in 331 BC before advancing into the heartland of Persia itself and occupying its other major cities and advancing from there into India. At this point, begins to describe the period of the Greek domination at the return of Alexander to Babylon, which was followed, later on by yet another period of Persian domination of Mesopotamia. During his stay in Babylon Alexander looked into the conditions of the irrigation and water works. Although the canal networks were in good conditions when they were left from the Archimedean’s time, he nevertheless ordered the cleaning of all the canal intakes on the Euphrates River. His major undertaking, however, was to solve the problem of the canal called the Popallacopas. This canal was used to pass the floodwater of the Euphrates down to the marshes and from there to the Persian Gulf while the Euphrates continued its course through Babylon in the reach, which was known, as the Babil River. Every flood season the Popallacopas closing dike was breached to pass the flood but the task of constructing it back afterwards was very difficult. The closure was necessary to ensure suitably high water levels to serve Babylon itself during the low water season, the closing operation of the intake, which was located in a ground of sandy soils, needed large working force of not less than 10000 men. Following the advice of his engineers, Alexander solved this problem by excavating a new head reach channel from another location above the first one but located in good and firm ground. Alexander ‘s next move was aimed at the reclamation of the marshy lands located near the present day of Najaf and to this end he constructed a massive earthen dyke between Babil River and the marsh north of the present day town of al-Shanafiyah as a preliminary step to dry the marsh and then prepare it for canalization and cultivation. Alexander premature death in June of the year 331BC however put an end to this work. In the aftermath of Alexander’s death his empire was divided between his generals; Persia, Mesopotamia and Anatolia passed to Alexander’s general Seleucus I Nicator who founded the Seleucid Empire (648-312BC) and succeeded in extending it also to cover the whole region of the Fertile Crescent. Various Persian satrapies (vassal kingdoms) such as Aria, Parthia, Fars, Media, Atropatene, paid taxes to the Seleucids but ruled with a great deal of independence. Seleucus inaugurated his reign by building a new capital for the empire, which was the Seleucia-on-Tigris on the western bank of the Tigris 60 kilometers northeast of Babylon, not far from the confluence of Tigris and Diyala.The lands of Mesopotamia at this point in time, had been already irrigated successfully by a system of canals maintained under the supervision of the State and agriculture was as usual the prime and most important basis of all the prosperity the empire had enjoyed. However, being a corridor between east and west Mesopotamia remained at the middle of conflicts with other outside powers and new rising tribal forces seeking to have their own kingdoms and empires. This was the case with the Parthians coming from the Persian heartland that had rebelled against the Seleucids after being vassals to them, and then vanquished their empire and took over its domains including Mesopotamia. In establishing themselves in Mesopotamia the Parthians moved their capital to Ctesiphon on the eastern bank of the Tigris opposite to Seleucia-on-Tigris about 58 BC, and remained the capital of the this empire until it was passed to the hands of the next Persian dynasty of the Sassanid. During the Parthian empire rule the economic prosperity was directly related to the upkeep of the irrigation systems and agricultural practices. Mesopotamia and the Persian lowlands of Khuzestan were the traditional centers of growing wheat, barley, and other cereals, while dates and other fruits were regularly produced and often exported. In the highlands of northeastern part of Mesopotamia and the Persian plateau, pastoralism and other forms of animal husbandry outweighed farming, although sowing various grains, most importantly wheat, as well as growing fruits, was also common. An earlier presence of rice in west Asia especially Mesopotamia might have also occurred through initial farming in eastern Persia and Transoxania. In the middle and south of Mesopotamia the Parthians looked well over the irrigation systems. In northeastern part of Mesopotamia and in Transoxiana the Kariz underground systems were used and maintained for the water supply of agriculture. The maintenance of all these systems was an important task of the Parthian Empire, often hinting on the strength or weakness of the government in certain periods of its history. It was also the case that in times of chaos and destabilization, that the maintenance of both the Kariz and the irrigation canals were neglected, causing further problems by weakening the agrarian, economy and causing further destabilization. Land tenure during the Parthian era did not differ much from the Babylonian or the Achaemenids eras. There were always two groups of people, either landlords or landless population, owners with large land holdings, usually members of the nobility and the court, controlled most of the productive land in the empire and, therefore families having such vast land areas would provide the basis of the later decentralized system under the Parthians. Another class of land-owning gentry, called the Azatan, also existed who were entitled to royal property in exchange for military service. The Azatan cavalry formed the hard core of the Parthian army and was mainly responsible for the Parthian success in external wars and in the quick initial expansion of the empire.

The Assyrians established their empire in upper Mesopotamia after crushing Babylonia. In this narration, we describe among other things the achievements of their great kings in building new cities and constructing waterworks for water supply of these cities and for irrigating the lands in their surroundings. The introduction of Sargon II for the Kariz irrigation system, which he had used to supply his new capital Dur-Sharrukin, is detailed. This was followed by describing the great works of his son Sinnecharib, who after building his new capitol Nineveh brought water to it from the upstream reach of the Khosr river by excavating a large canal called Kisiri Canal and creating a reservoir. He even arranged to release the floodwater into a nearby depression, which he turned to a reserve for wild animals. Finding out that the canal discharge was not enough for all his cultivations and parks he tapped springs in the surrounding hills and mountains and collected their water in eighteen canals to supplement the reservoir. In this scheme he constructed also all the required engineering structure such as weirs and dams. However, his biggest achievement in this work was in drawing water from the Khazir- Gomel River from a point northeast of Nineveh and bringing it to the same reservoir by excavating a very large 50 kilometers canal. The canal is named as the Bavian canal in reference to the name of the location of its intake. Full description of the site, the diversion weir needed, and the intake structure are presented and illustrated by photographs and maps. One of the major structures of this canal, the Jarwan aqueduct, which was employed to pass the stream over a very wide wadi, is described in details as it gives insight of the ingenuity of the people of that time and shows how they had dealt with such cases.Sinnecharib was also responsible for constructing more large hydraulic works; of these the Kariz system of Bastoura- Erbil is fully described and his improvement on the water supply scheme of the city of Kalhu (Nimrud) and its irrigation project originally built by king Ashurnasirpal II (883- 859BC) are also presented. Moreover, a general idea is given in this paper on agriculture and the types of crops and vegetable and fruits grown to indicate the prosperity of this empire. However, as always in similar cases, this empire was distained to fall after internal conflicts over the throne and external attacks from outside envious enemies. Some authors even add another reason, which is the drought which had hit the heartland of Assyria in later stage. So the story of the Assyrian Empire ended in the year 612 BC when Nineveh fell to the combined forces of the Babylonians and Medes and the defeat of its last king Ashur-Uballit who was defeated in his last stronghold in Haran which took place taken in 610 BC.

Sumerians were the first People in history to invent the cuneiform script, which made the reporting of their achievements possible. Therefore, this had marked the beginning of written history. Moreover, their experience as pioneers in practicing large-scale irrigation is detailed in this paper, which also describes the intricate canal networks systems they had constructed together with the engineering works related to them. The land was flat and the two rivers had built themselves to higher levels than the surrounding lands by the continuous silting process, so gravity irrigation became possible and the people took the opportunity to construct these networks and establish their communities here. Description of the political and social developments, which led to the establishment of the city-states, is also given together with a list of the most prominent ones, and their locations are shown on a map indicating the heartland of Samaria in southern part of Iraq; close to the Persian Gulf. Wars between some city-states over water rights are detailed with their results in excavation of new canals, which are described here. A vivid description of the irrigation canals and the hydraulic structures that were needed and built are also presented which show that the Sumerians were versed in hydraulic principles, while in illustrating their methods of land preparation, seeding, irrigation and harvesting indicates they were skillful farmers. Moreover, the tools and implements invented for field operations such as those for water control, land preparation, seeding and harvesting, which are fully described, show that they were also inventors.The type of crops produced are given special attention and the abundance of yield they obtained was outlined indicating that surpluses had encouraged trading with other parts outside Samaria and so new commercial relations were developed. The economic aspects of this civilization such as wages and loans for farmers, work specialization and the appearance of new professions to meet cultivation requirements were described. The social hierarchy on which social relations and organization of work was based are presented especially those related to the agricultural and irrigation works which are given their share of explanation and discussion. Flood protection works needed for better safety from the Tigris and Euphrates rivers recurrent floods were routine practices of the Sumerians to protect themselves and their lands from the grave dangers of these floods. Therefore, they excelled in them, while canals maintenance by constant dredging of the silt brought down by the two rivers every year was a constant concern. The Sumerians over long period had accepted within them some other people namely, the Akkadians who intermingled with them, lived in their cities, and even mixed with them in marriages. This explains how a smooth transition of power had resulted in the rise of the Akkadians King Sargon, after he had started as a high-ranking official at the court of (Ur- Zababa) the last Sumerian king and replaced him to mark the start of the Semitic Akkadian domination, which lasted almost 200 years to 2150 BC. Sargon managed afterwards to unite all the city-states and establish the first empire in the world extending well beyond Sumeria, so it was said that his influence was felt from Egypt in the west to India in the east.Finally, this paper presents briefly the various theories behind the decline of the Sumerian- Akkadians power and the reasons for passing this to the new rising city of Babylon, which took over this civilization to establish its own.

Remote sensing is the collection and interpretation of information of an object, areaor phenomenon by a recording device that is not in physical or intimate contact with the object or phenomenon under study. It generally refers to the use of satellite borne or airborne sensors to capture the spectral and spatial relations of objects and materials on Earth from the space. This is done by sensing and recording reflected or emitted electromagnetic radiation from the objects. A brief history of satellite remote sensing is given in this review but the bulk of it is devoted to the scientific satellites launched into orbit and their sensors tracking, and presenting changes in water resources fields. The used technologies and satellite systems for monitoring movements and changes include American GNSS, GPS, the Russian GLONASS, Europe’s European Satellite Navigation System (GALILEO), China’s COMPASS/BeiDou, the Indian (IRNSS); Japan’s (QZSS) and many others. Details are presented on the present (LANDSAT), the Moderate Resolution Imaging Spectroradiometer (MODIS), as well as Synthetic Aperture Radar (SAR), and RADARSAT, JERS‐1, and ERS, which are developed by various countries, especially the USA. These sensors have the refined capability of providing estimates of variables, which depending on the purpose and design of the sensor, can follow critical issues related to water management problems. This review presents examples of actual studies carried out including; building databases of small dams and lakes on regional scale, derivation of volume vs. elevation and surface area vs. elevation of hundreds of reservoirs around the world, various bathymetric reservoir surveys, siltation of reservoirs and catchment areas erosion problems, monitoring of water quality changes, and above all monitoring dam deformation and stability problems of dams. The presented case studies cover the use of these different sensor together with the imagery used, their sources, methods of interpretation, validation and gives presentation of the end results. This review, which is only a very brief presentation of satellite remote sensing applications concludes that; in spite of the large volume of research done on this subject so far, which this review cites some of them , the expected future developments in satellite remote sensing technology coupled with advances in algorithms and models used in refining satellite imagery and validating the results will bring more accurate results and less laborious treatment work in addition to wider scope of applications.

During and after the construction of Mosul Dam, in Iraq, all the studies expressed a clear concern on the fact that the region of the dam suffers from extensive presence of soluble rock formations that might undermine the safety of the dam with its large reservoir. Most of the studies dealt with foundation treatment and safety hazards due to the dissolution of gypsum and anhydrite. To overcome the problem, grouting operations were performed. The seepage of water continued and this highlighted the possibility of the dam failure. Different grouting techniques and methods were suggested but the results were the same. Finally, it was decided to limit the maximum operation water level to EL. 319 m (a.s.l.) instead of EL.330 m (a.s.l.). This recommendation has remained in force up to now with the loss of sizable storage of irrigation water and power potential

Mosul dam was constructed on the beds of Fatha Formation (Middle Miocene). The beds of the formation are about 250 m thick composed of Marls, chalky limestone; gypsum, anhydrite, and limestone form a layered sequence. They are highly karstified. As a consequence, plenty of grouting operations were carried out to fill all the cavities, fractures, joints and to stop the seepage under the foundation of the dam. The main grouting operations were Blanket grouting and deep grout curtain. It was necessary to perform an extensive maintenance program to control the seepage process within the grouted zone to stop dissolution of gypsum and protect the safety of the dam.

Dissolution of gypsum and anhydrite at the foundation of Mosul Dam continued after its construction since 1986 onwards. After impounding, acceptable residual permeability could not be reached and new areas of high grout takes appeared in some other locations. New grout mixes were tested and even methods of delivering and injecting large grout quantities were developed. Sandy mixes were developed by adding certain weight of sand to the cement mix. In addition, pouring gravel after completion of grouting in large takes' zones was performed. As a result of gravel addition, it was concluded that it was not effective and very difficult to pour. Massive grouting was used where bentonite was added to the mix. Piezometric observation was used for checking the conditions of the grout curtain and the detection of problematic areas where additional treatment was required. Massive grouting, however, did not stop the dissolution processes altogether and it seems that it is not likely to do so in the future. The continuation of this program year after year does not preclude some bad implications. More research work is required to improve massive grout durability by adding chemicals which may interact with gypsum beds and hinder dissolution. This can help to improve gypsum resistance and increase its stability. Mathematical models might also be used to understand the mechanism of cavities formation and collapsing.

Mosul dam was built on the River Tigris northern part of Iraq during the period 25th January, 1981 and finished on 24th July, 1986. The foundation of the dam lies on the Fatha Formation. This formation is composed of alternating beds of marls, limestone, gypsum and clay. The beds of this formation are highly karstified. After impounding, several sinkholes developed within the vicinity of the dam site. The surface expression of the sinkholes suggests that they are caused by underground collapse.The appearance of the downstream sinkholes is most likely related to fluctuations in the tail water level of the main dam during operation of the dam and the downstream regulating reservoir. In addition, water seepage also was noticed in various areas indicating the dissolution of gypsum and anhydrite from the foundation. During the period February-August, 1986 the dissolution intensity ranged from 42 to 80 t /day.

The basins of the Tigris and Euphrates Rivers Cover an area of 917103km2 distributed between Iraq, Turkey, Iran, Syria and Saudi Araba. The population within the basins reaches about 50 million inhabitants. The flow of the two rivers is decreasing with time. This is due to the construction of dams and irrigation projects in the upper parts of the basins and climate change. This has an impact on the quality of water within the two rivers. Iraq being the lowest riparian country is highly effected. Analysis of water quality of the water indicates that the salinity of Euphrates water is increasing with time and on the Syrian- Iraqi borders, it is of unacceptable level where it is higher than what is recommended for Irrigation. The Tigris water quality becomes alarming once the river enters Iraq and at Baghdad, it becomes unsuitable for irrigation. To overcome these problems, riparian countries must cooperate seriously to take measures to improve the quality of water within the two rivers.

Climate change is affecting the hydrological cycle all over the World. The effect on arid and semi-arid regions is relatively more. The Middle East and North Africa region is one of the biggest hyper-arid, semi-arid and arid zones in the world where the long-term average precipitation does not exceed 166mm per year. The Tigris and Euphrates basins are located within the northern part of the Middle East. Future projections  indicate  the  considerable  reduction  in  water  resources  as  a  result  of drought and population growth. North Atlantic Oscillation (NAO) is responsible for the  change  in  climate  over  the  Tigris  and  Euphrates  basins.  This  is  causing  a decrease in rainfall and a consequence decrease in the flow of the rivers. In addition, the  temperature  is  increasing.  All  these  variables  are  causing  sea  level  rise, increasing dust storms and deletion of groundwater resources. It is believed that quick actions are required to minimize the effect of climate change. This includes prudent water resources planning and good regional cooperation.

Iraq as a country is now suffering from Climate Change Impacts in similar or even worse ways than many other countries of the world. The manifestations of these climate changes are being felt in global warming, changes to weather driving elements and sea level rise. Increasing temperatures, declining precipitation rates and changed distribution patterns together with increasing evaporation are causing water stress in Iraq. However, they trigger other changes in a sort of chain reaction; such as droughts, desertification and sand storms. Iraq is not even safe from the consequences of sea level rise where the southern part of the Tigris- Euphrates delta is threatened by inundation and Iraq’s ports and sea coast line are endangered by such projected rise. So far the agricultural sector in Iraq has been hit very badly by the reduced water availability for arable lands; whether rain fed lands as in the northern part, or irrigated lands using the declining discharges of the Tigris and Euphrates Rivers as in the southern and middle parts. These discharges have already been additionally strained by the unfair sharing practiced by Turkey from which most of the two rivers’ water resources originate. The present negative climate change trends seem to be continuing in the future as it is obvious from all projections and studies being performed so far. Loss of cultivable land to desertification, recurrent droughts and sand storms and declining agriculture are the pattern of change in Iraq’s already fragile environment; and this will result inevitably in much more distress for the population in the future and will lead to social unrest. These will add to the great pressures facing all future governments unless the government takes protective planning and solutions.

Global warming is hitting all parts of the world for the last fifty years due to Global Climate Change and it is expected to continue in the future in an increasing trend unless the present mode of CO2 emission is limited or reversed. This is manifested in the rising temperature over land and the changes induced in the general weather circulation patterns over land and oceans. The Tigris River catchment as most of other parts in the world is suffering from increased temperatures and reduced precipitation contributing to reduced water resources elements all over it and reduction of the river stream flow itself. Studies using the soil and water assessment tool SWAT were performed on the five Tigris River tributaries basins in Iraq in order to assess these impacts. This paper summarizes the results of those studies, the characteristics of each of the five basins, and illustrates the application of SWAT as a tool for future predictions. Moreover, it explains in more details the work done on one of the basins as an example, summarizes the results of the five studies and then analyzes these results and discusses the expected future outcomes. The final conclusion which can be drawn is that severe shortage in all water resources elements will occur over the five basins and the Tigris River stream flow will suffer a considerable decline. This situation demands that policy makers in Iraq should take steps immediately to improve water and soil management practices to try and reduce as much as possible the expected damage that will hit all water using sectors.

Dam safety hazards towards human communities have increased tremendously during the last decades. They have resulted from dam safety problems leading to failure and being exasperated by the large losses at downstream areas due to increasing populations and land use. In this work, an attempt is being made to review the procedures being followed to reduces these hazards by improving dams safety standards. Classification of dams by their potential hazards are explained as used today for prioritize remedial actions in various countries of the world. The guiding principles of these classification are indicated and they are based on height of such dams and their storage and linked to the potential damage and harm they can create. Normally such classification and follow up actions are supported by various legislations and regulations issued by the respective governments. Moreover, conventions signed by riparian countries promote cooperation on mitigating safety problems of dams on transboundary rivers. Examples of such legislations and conventions are mentioned. Looking for having safer dams is an objective continually which is being pursued as more dams are needed in the future while existing dams continue to serve their objectives. Therefore, using lessons learned from previous failures is recommended taking the question of loss of life as a main doctrine.

Earthquakes may cause failure or profound damage for dams. Factors contributing to this are, magnitude on the Richter scale, peak horizontal and vertical accelerations, time duration, in addition to the epicentral distance, nature of foundation rock, criteria of the design, and finally, if appropriate type of dam and materials has been used.  Extensive lists of dam failures and damaged once are presented with many case histories. Most failed dams were tailing dams or hydraulic fill dams or small earth fill dams, which reflect the weight of the design and construction factors. Embankment dams, normally, are less tolerant to ground shacking than concrete dams. While rockfill and RCC dams have shown good performance. The developments of design methods and criteria are traced here, from the early use of the pseudoptotic method to the more rational dynamic analysis, which is used nowadays making construction of very large safe dams in seismic regions possible. The method adopts peak ground accelerations from anticipated earthquakes as inputs to the analysis which produce a full spectrum of the factor of safety during any considered event. This has led to increased use of seismic instrumentation to produce seismographs of actual events in the free field, and on dams hit by earthquakes for comparison with outputs of this analysis and for future use for similar dams in similar circumstances, and to decide on rehabilitation measures. The safety levels to which any dam is to be designed are defined in terms of the Maximum Credible Earthquake, Safety Evaluation Earthquake, Maximum Design Earthquake and other similar terms. Dam repairs after sustaining earthquake damages are described in real cases and upgrading of older dams to withstand higher expected seismic events are also treated here and supported by case histories.

Overtopping is one of the most serious modes of failures for all dams causing great numbers of human fatalities and material damages. Statistics show that overtopping failures are the highest, especially for embankment dams. The main reason for this is the erroneous prediction of the inflow design discharge, which has resulted from lack of realistic flow data and imperfect hydrological procedures. Failure in most cases occurs when the inflow exceeds the spillway design capacity, but to a lesser extent from the buildup of very high wave setup and runs up. This has led to active efforts in upgrading dams for such occurrences, by either upgrading spillways, adding auxiliary spillways, increasing freeboard by either heightening the dams or the parapet walls on the crest. Advancement in predicting the safe inflow discharges are also made by adopting such procedures as the calculation of the Probable maximum flood based on predicting the Maximum Probable Precipitation or using statistical methods by treating long records of available flow data. Recently, another challenge has come up facing dam owners and builders who are represented by the climate change impacts on the hydrological cycle; this has put a new responsibility to the governments to issue new regulations and plans to mitigate these impacts reducing failure possibilities and improve dam safety against overtopping.

Dams construction is an old art practiced by man since thousands of years. History of dams shows great innovations in this field, but failure cases, however, indicate gaps in human knowledge of safety measures that could have stopped such failures. Available statistics show of a great boom in building dams during the past century and indicate at the same time large number of failures associated with losses in human lives and material damage. Uses of these dams during this period, apart from flood control and storing water for irrigation were also for hydropower generation, navigation, drinking water supply, recreation and in mining operations as tailing dams. Reduced dam safety leading to failures, accidents and higher safety hazards were caused by insufficient knowledge of the geological conditions and in using wrong or deficient foundation treatment. Dam safety was compromised in cases of insufficient hydrological data and design of inadequate spillways. Misinterpretation of the seismic conditions of the area and adopting seismic criteria compatible with such seismic conditions is also added as one more reasons of failures. Human mistakes and errors have undermined safety in many cases in the operation of dams leading to grave safety issues including many failures. Safety hazards also were exasperated by increasing population and land use in the downstream areas of dams and by failing to do necessary inspection and maintenance or upgrading works.  More emphasis over  dam safety measures is needed now in our existing dams and in their future development of dams if they are to continue delivering their benefit without causing harm to human communities.

Dam Safety and dam incidents are treated here looked at from the "Human Factors" perspective. An attempt is made to explore these factors as an important drive in impairing dams’ safety and increases their risks. Distinction is drawn between the "Normal Human Caused Incidents" and the "Extraordinary Human Caused Incidents" together with the description of their root origins and subsequent consequences. The first type includes unintentional mistakes, errors and flaws committed by the operators of dams inadvertently, in addition to negligence, lack of experience or overconfidence. Such failings can happen in manual operation of dams, or through the use of their Supervision, Control and Data Acquisition (SCADA) systems as in industrial control system (ICS). They can occur also due to flaws in software or even in the application of information and communication technology (ICT) in remote control operations. As for the second group; the extraordinary human factors, they are defined here as those committed by man with the full understanding of their possible damage. They are done purposely for destabilizing dams after thoughtful and carefully meditated decision making process and they are manifested in acts of war, sabotage and terrorists actions. In this modern age, these acts are characteristics of hackers’ attacks on dam(s) operating systems. This is done through the use of cyberspace by the widespread interconnected digital technology with the accompanying advances in the communication technologies. As such, these technologies have made remote control of such systems possible. Not limited to this, dams remain now, as they were always in the past, the obvious targets in wars and conflicts to inflict losses on the enemy and to use them as weapons, and for terrorism actions for challenging governments. Examples of the aforementioned threats are described with examples given from real cases to elucidate the dangers involved. Lessons to be learned from these incidents are derived and recommendations are presented to be followed to avoid risky situations.

The awareness to tailings dam safety monitoring and reviews has increased by the catastrophes resulting from failures of such dams worsened by increasing tailings waste and construction of larger dams. The losses born by the mining industry from high costs of compensations and environmental rehabilitation work have brought this matter into focus. In the present article the need for safety monitoring programs of tailings dam is highlighted and mode of failures and factors leading to them are described. Basic principles of such programs are investigated with all phenomena needing observation described and their impacts explained. As in conventional dams this work is carried out by visual inspections and use of similar methods and instruments. In similar manners in both types of dams’ observation and measurements are done for measuring seepage water quantity and quality, phreatic surface level and pore pressure and total earth pressure values in addition to deformation measurements; and all are done by similar devices and methods such as weirs, piezometers, inclinometers, settlement plates and geodetic surveying. Basic differences between safety monitoring systems of the two types of dam, however, are presented in a tabular form. The continuity of safety monitoring of tailings dams is emphasized not only during the long construction phase but also after that in the abandonment and closure phase which can last indefinitely in order to watch for possible adverse effects on the environment and ecosystem due to the winds eroding and carrying of poisonous tailings contents, in addition to

contaminated seepage water entering surface water streams and ground water. Justifications for using real time monitoring systems for recording and transmitting all data to the control center are presented with emphasis given on savings in both labor and time and need for the discovery of warning signs enabling raising earlier the alarm of possible failure or incident and the early taking of preventive measures. In this article it is argued that, in spite of the large investment of installing and running cost of comprehensive dam safety monitoring systems in tailings dams, such costs are justified as they form only a small percentage of the total investment in the tailings facilities projects, and may save huge costs if failure does happen. Such systems may be considered as an additional insurance against such events.

Dangerous occurrences affecting dams take multiple forms, but seepage caused cases are the most numerous. Some of the cases are related to the geology of the foundation and the magnitude and type of discontinuities in the rock mass of the dam. Other are mainly due to of construction material in earth fill dams. Seepage occurs in all earth fill dams regardless of its materials, and seepage water can daylight at the downstream face causing erosion, piping and sloughing and instability; unless certain measures are taken. Instability can be controlled mainly by adding, filter material zones at the contacts with the clay core, chimney filter drain at the downstream part of the dam, filter zone or bench at the toe together with the drainage blanket under the downstream part of the dam. Seepage within the dam is enhanced by cracks which may result from uneven settlement of the dam due to different elastic behavior of the foundation materials, hydraulic fracturing, and differential settlement of parts of the dam or due to ground shaking in earthquakes. Preferential seepage paths can develop in such cracks, especially if the fill material is dispersive or suffusive. Similarly, such paths may develop along the contact surfaces of conduits installed under dams as outlet structures due to the low degree of compaction as a result of narrow trench dimensions. Using properly designed filter and drainages can reduce seepage quantities and the erosive force which causes internal erosion. In dam’s foundation grout curtains or other type of cutoffs can reduce the hydraulic head and hence uplift under the dam and hinder seepage.  Drainage, however, remains as the most efficient method in controlling this uplift in artesian conditions under dams, especially under concrete gravity dams. Generally, such drainage may take the form of drainage blanket and use of filters material. 

Sedimentation of reservoirs has its negative impacts on dams, first by reducing useful storage, altering the benefit/cost ratio originally calculated for the dam, and second by reducing the dams’ capacity for flood routing; increasing flooding hazards on the dam itself and for the downstream. More problems can be created by sediments and floating debris during floods on outlet structures by clogging them and thus creating dangerous situations, or damage trash screens leading to even more problems. If these debris and coarse sediments are allowed in, then they may damage dam structures such as gates, spillways intakes in addition to chutes, stilling basins and power penstocks by the mechanical abrasion impacts of such sediments on them. Frequent inspections, especially after floods must be made to ensure proper functioning of such structure and take actions for reducing the damage. In small reservoirs, dredging; although it adds to maintenance cost, may ease the problem, but in very large reservoirs, this may prove unpractical. Designers, therefore, have a duty to consider sedimentation problem seriously in the initial stages of design by: checking the anticipated accumulation of sediments, allowing enough storage free from siltation, foreseeing their negative impacts on intakes and outlet structures and taking design measures to reduce these impacts. At the same time, dam stability calculations shall have to provision for the anticipated new conditions of silting up at the face of the dam. Operators of dams, on the other hand, shall have to keep open eyes for all the negative issues created by sediments and floating debris, repairing damages caused by them and take measures to reduce their impacts in the future.

Concrete dams age as all man-made structures. Being subject to various external influences and internal reactions their ability to withstand them diminishes with time. Description of these factors are given here. The manifestations of aging signs are cracking, expansion, spalling and scaling of concrete surfaces, change of color and efflorescence, gelatinous discharge, crumbling of concrete masses, in addition to abrasion and cavitation of surfaces. The mechanisms of the actions leading to these damages are described and supported by many examples and case studies. The general conclusion drawn is that nothing can be made to extend the lives of old dam indefinitely, but a lot can be done to elongate their useful service with repair and upgrading works until technical considerations prove them unfeasible or their cost become prohibitive.

Embankment dams undergo aging process due to the impact of different factors which can be attributed to geology of the site, design of the dam, materials selection and procedures followed in constructions. In the foundation the presence of faults or shearing planes, karst, compressible clayey material, soluble rock, and soft rock may establish conditions leading to high total settlement or differential settlements of the dam and its cracking. Deficient and deteriorating seepage control measures such as grout curtains or diaphragms enhance seepage flow leading to internal erosion and piping which endanger dams’ stability. Improper filling materials used such as dispersive clays and gap graded granular material show their bad influence after long time by creating conditions inducive to internal erosion and piping. Use of improperly designed and placed filter zones and drainage blankets can end in clogging of such filters and drainage blankets leading to the rise of the phreatic surface level and increasing uplift causing again conditions of internal erosion and piping and undermine stability. This work attempts to give an overview of these conditions and cite many case studies of rehabilitation works carried out in dams after long years of service. The conclusion reached is that rehabilitation works if done early when problems are discovered play well to elongate the service life of dams, but normally they require large investments. Sooner or later owners of such old dams will come to realize that more rehabilitation works, neither technically nor economically, are feasible and that more of such works are not possible. In which case they will come think seriously of decommission such expired dams.