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~ For integration into Indus River

Upper course
The Indus flows northwest through the high plateau of Ladakh into the disputed Kashmir region. It continues past Skardu and is joined by the Shyok River. It then curves to the north to go around the Nanga Parbat and Haramosh massif, then bends west and finally southwest. It is then joined by the Gilgit River.

Near the town of Thakot, the Indus juts sharply to the east in what appears to be a prehistoric meander that became entrenched.

The Tarbela Dam, near Tarbela, is a major dam on the Indus. The Siran, a small and seasonal stream, joins the Indus around this point. Downstream of Tarbela, the Indus changes to flow in a broad valley for 50 km before reaching the Attock Gorge. Also near Attock, the Kabul River, the Indus's largest western tributary, joins it.

The Soan River joins the Indus about 8 km upstream from the Jinnah Barrage.

Near Kalabagh, about 160 km downstream from the Attock Gorge, the Indus turns west at an almost right angle. It passes through the Salt Range and across the Kalabagh Fault before turning south again. At this southward bend, the river leaves the mountains for good and its valley opens up into a wide plain. From here to the sea, 1150 km away, the Indus is a braided stream surrounded by an active floodplain. During the rainy season, or whenever there is significant snowmelt in the mountains, the floodplains are inundated. The surrounding plain is "almost featureless", except for isolated hills where the bedrock crops up above the ground. The river's slope is very gentle throughout this portion; only 4.8 cm per kilometer.

The Indus's confluence with the Panjnad is just above the town of Mithankot.

Lower course
The lower Indus is situated on a vast alluvial plain of 50,000 square kilometers, between the mountains of Baluchistan on the west and the sands of the Thar Desert on the east.

The area around Ghotki on the left (south) bank of the Indus consists of a floodplain ranging from 15-25 km in width. This floodplain is cut up by a series of crescent-shaped scars running parallel to the Indus, with the open sides all pointing northwest. These scars represent the former course of the Indus, from the same general phase of activity as today. Further southeast, a series of bluffs around Khangarh mark the ancient watershed between the Indus and the Nara — the Nara used to have a whole separate system of rivers that were its tributaries, but they dried up at some unknown date.

The area on the right (west) bank of the Indus below Larkana is a densely populated rice-growing area, sometimes called the "Garden of Sindh". Its continued prosperity — a rarity in Sindh because of the Indus's constant shifting — is because of two waterways, the Ghar Branch and the Western Nara. They both originated as natural spillways, but human activity has essentially turned them into canals by maintaining their courses and scouring them to keep them from silting up. This likely began around the 13th century.

In central Sindh, the Indus cuts through the northern tip of the Kot Diji hills — a limestone cuesta extending to the south — through a rocky gap at Sukkur. Here, the river is now dammed by the Sukkur Barrage, which was built from 1923 to 1932 under the British Raj. Seven canals are drawn off from the Indus here, which together provide irrigation to 8 million acres of farmland — 75% of all agricultural land in Sindh. One of these, the Nara Canal, is to supply the old natural course of the Nara river.

Just to the south of Sukkur there is a small gap in the Kot Diji hills, the Aror gap, which the modern Nara Canal passes through. The great city of Aror, the ancient capital of Sindh, once stood on both sides of this gap. It has been proposed that the main course of the Indus once flowed through the Aror gap, but this is unlikely because the gap itself is too narrow. Floodwaters from the Indus have occasionally flowed through the Aror gap in the past, though, and there must have been some sort of water flow at least seasonally if not year-round during Aror's heyday.

From Sehwan south to Thatta, the Indus flows right up against the high ground at the western end of the alluvial plain. This keeps the river from shifting its course further west. In the first part of this section, between Sehwan and Unarpur, the river makes a big curve to the southeast. At Unarpur, it bends sharply to the southwest. There are no major bends from Unarpur to the sea — there is still a lot of meandering, but the river's general direction is consistent throughout this whole stretch.

A second unexpected gap through limestone hills occurs at Hyderabad, where the Indus skirts the western outcrop of Ganjo Takar.

Delta
Historically, the Indus had some 16 major mouths, but since the construction of the Kotri Barrage, the downstream water flow has been significantly reduced, and only the area between Hajamro and Kharak Creeks receives water from the Indus. The main outlet is the Khobar Creek.

Since the construction of the Kotri Barrage, the water flow further downstream has been reduced dramatically — for most of the year, no flow reaches the mouth at Khobar Creek. Freshwater from the Indus only reaches the Arabian Sea during August and September, when the river reaches peak flow during the southwest monsoon. Meanwhile, saltwater from the ocean actually flows backwards, going upstream along the course of the lower Indus as far as 75 km inland.

When the delta distributaries of the Indus shift, they tend to do so suddenly rather than gradually.

Former river courses

 * The "Jacobabad course" is very old, but later floods have scoured its bed so that its channel is well preserved. It first becomes detectable near Kandhkot and then goes west toward Jacobabad before becoming untraceable again, obscured by later alluvial deposits.


 * The "Shahdadkot course" is now marked by a system of bars and channels which first emerges southwest of Jacobabad and then travels southwest to Shahdadkot. It then becomes untraceable.


 * Another system of bars and channels emerges northwest of Warah and then goes south for some 30 km through the depression now occupied by Hamal Lake. Its crescent-shaped meanders are typical of the region. It probably represents a downstream continuation of either the Jacobabad course or the Shahdadkot course, indicating that the river once flowed up along the northwestern edge of the modern alluvial plain down towards Lake Manchar.


 * The "Warah course"


 * The "Kandhkot course"


 * The "Khairpur course", aka the Lohano Dhoro, is "almost certainly a continuation of the Kandhkot course" — the two are very similar in form. It begins at the bluff just southwest of Khairpur


 * The Sanghar course is not detectable on the ground, but can be seen as a series of flow lines in aerial photographs. These are first visible about 20 km northeast of Nawabshah, and then they continue southeast along the edge of the desert. At Sanghar, this watercourse was joined by a small western tributary and then bent due east before joining the Eastern Nara. The Sanghar course appears to be very old, possibly the oldest in the region. Like many of the Indus delta distributaries, it has a narrow channel and seems to have been fairly stable. Just before its confluence with the Nara, its channel becomes deeper and especially well-defined, probably because of erosion caused by floodwaters.
 * The Samaro course also first appears in the area around Nawabshah. The old city of Brahmanabad, aka Mansura, was located on the west bank of its clearly-defined channel. It may represent the river called Jalwali in accounts of the Muslim conquest of Sindh, since that river is described as lying east of Brahmanabad, but it may be the Manjhal instead. Not far downstream from Brahmanabad, a separate right-hand branch splits off and heads south, but it soon becomes untraceable because later alluvial deposits have covered up its own. The well-defined left-hand branch, meanwhile, goes almost directly southeast past the town of Samaro and then bends to the west, finally joining the Nara via the Dhoro Badahri. The Samaro course probably declined gradually at some point between the 9th and 16th centuries.

Delta mouths

 * At the northwestern extremity of the Indus delta is the Gharo, which runs east-to-west for about 64 km along the southern border of the Kohistan region. The Gharo is just a tidal creek unconnected to the river, but it used to form the mouth of the Kalri branch.
 * The Kalri, which by the late 1800s was just a flood channel of the Indus, was once a major branch of the river. It branches off a bit northeast from Thatta, then flows westward. Historically, the Kalri flowed out to the sea through what is now known as the Gharo, but at some point it shifted at a point about 11 km west of Thatta so that it flowed south and joined the Baghar instead. The 16-19 km west of this point then silted up, leaving a gap where some traces of the old channel can still be seen. The lowest reaches of the channel, though, were kept in water by tidal action from the Indian Ocean, becoming the Gharo.
 * The Baghar splits off from about 10 km south of Thatta and then flows west. It joins the sea through several mouths: the Rishul, the Shisha, the Piti-ani, the Khudi, and the Piti. Technically, the name "Baghar" only applies to the channel until the Shisha mouth; beyond this, the western reaches are known by other names, such as the Khara and the Raho. The westernmost point of the Baghar is the Piti mouth, about 19 km southeast of Karachi. Although now just a flood channel of the Indus, the Baghar was historically a major branch of the Indus, and as late as the early 1800s was still a perennial stream.
 * The Gungro is now an irrigation canal whose water supply is now artificial, but it historically would have branched off somewhere downstream from the Ren branch. It flows south and eventually joins the ocean through the long Sir Creek; their combined length is about 193 km.

Geological history
The Indus has existed for at least 45 million years, making it one of the oldest known rivers. It is thought to have formed shortly after the collision of the Indian and Eurasian Plates (which had already happened by 45 million years ago), and it was already in existence by the Early-Middle Miocene, when the Himalayas were formed (20-25 million years ago). According to Qayyum et al. (2002), the palaeo-Indus existed in the early Eocene as a river flowing westward north of the Himalayas. It then met with the Katawaz Ocean, a bay of the larger Tethys Ocean, at a place called the Katawaz Delta. Sediments from this delta were then fed westward and are now exposed in the mountains of Makran in Pakistan and southeastern Iran. The formation of the Sulaiman Mountains later shifted the course of the palaeo-Indus to the southeast by 200-300 km, but other than that this course has remained following the Indus-Tsangpo Suture Zone ever since this early period.

Qayyum's version: the collision of the Indian subcontinent with Eurasia caused the uplift of the early Himalayan highlands sometime between 66 and 55 million years ago. The Katawaz remnant ocean still existed to the southwest of these highlands. The palaeo-Indus was the northern of two streams that flowed westward from the early Himalayan highlands, along the Indus-Tsangpo Suture Zone for 2,000 km. This river system began eroding the early Himalayan highlands and depositing the sediments in the Katawaz remnant ocean, forming the Katawaz delta and the Khojak submarine fan complex. The Katawaz remnant ocean was the main depocenter for Himalayan sediments during the early/middle Eocene; by this point, the main Tethys north of the subcontinent had almost closed. As the subcontinent continued to drift northward, it pushed the Himalayas up higher, which in turn caused an increased amount of sediment to be carried by the palaeo-Indus, and over the course of the late Eocene/early Oligocene, the Katawaz delta gradually expanded toward the southwest. The Katawaz ocean remnant remained the main depocenter of Himalayan sediments in the late Oligocene.

In the early Miocene, around 21-19 million years ago, there was a sudden southward shift in the course of the Palaeo-Indus. It now came to follow its present southward course, bypassing the Katawaz delta entirely. According to Qayyum, this was because of "rapid uplift of the Baluchistan Ranges from north of the Khyber Pass southwards during continued Himalayan suturing". In particular, there was "acute transpression and major uplift" in the region from Waziristan to north of Kabul, which left the Palaeo-Indus unable to erode through it. Thus, a more easterly course was easier and stream capture happened. Before this, the present-day lower Indus course was probably occupied by "a minor, possibly intermittent desert stream carrying very little sediment to the Indian Ocean". The final closure of the Katawaz remnant ocean probably happened at the beginning of the middle Miocene, sometime around 13-18 million years ago.

Another shift happened around 12 million years ago, when the drainage divide between the Indus and Ganges-Brahmaputra river systems appears to have gradually shifted to the west, causing the Ganges-Brahmaputra system to grow at the expense of the Indus. This may have been because of counter-clockwise rotation of the Indian subcontinent. As a result of this change, the Indus delta no longer became the main depocenter for Himalayan sediments — that instead went to the Bay of Bengal.

According to Najman et al. (2003), the palaeo-Indus first followed its modern course, cutting south through the Himalayas and into the foreland basin, about 18 million years ago. This course's relative stability is because the suture zone keeps its upper course pinned, and then in the foreland basin it is flowing along a strike-slip fault. Some other major rivers, such as the Nile and Amazon, have experienced much more significant course changes in the meantime.

A major change happened around 15 million years ago when the river's Punjabi tributaries – which, up to this point, had been flowing to the Ganges instead – shifted course to join the Indus. The reason for this is unknown, but it was likely linked to the Pliocene uplift of the Salt Range.

History of the upper course
In Punjab, the tributaries of the Indus began to incise sometime after 8,000 BCE. The presence of Harappan sites within the incised valleys of the rivers indicate that they had already become entrenched by 3,200 BCE.

History of the lower course
In upper Sindh, there are well-preserved Harappan sites on the alluvial plain, including Mohenjo-Daro, which indicates that the Indus mega-ridge has been stable in that region since then. "In contrast, in lower Sindh, just a few Harappan sites have been discovered on the eastern delta plain, supporting the idea of a switch of the fluvio-deltaic depocenter to the west. Any settlement on the alluvial plain that may have existed in the southwestern part of Sindh is probably buried under later fluvial sediments."

The earliest surviving historical sources documenting the course of the Indus are the accounts left by the ancient Greeks, around 300 BCE. These accounts describe two islands formed by the Indus: the larger Prasiane in the north and the smaller Patale in the south. No unexpected rocky gaps through the Kot Diji hills were mentioned, and the main course of the Indus probably flowed northwest of Sukkur. From there, it must have flowed south towards Nawabshah, but the precise course is untraceable.

This main course formed the eastern boundary of Prasiane. The western boundary was formed by a branch of the river that split off at some point and then roughly followed the later Jacobabad course along the western edge of the alluvial plain. This western branch then flowed south into Lake Manchar, and then rejoined the main Indus trunk somewhere around Nawabshah. The "island" of Prasiane in northwestern Sindh continued to exist for at least a thousand years, gradually getting smaller as the western branch shifted eastward.

Further south, the "island" of Patale was formed by two major branches. There are two candidates for the eastern branch: the Samaro and Sanghar courses. The Samaro course, which was definitely flowing about 1,000 years later at the time of Brahmanabad, may not have remained active for that long. That may make the Sanghar course a more likely candidate for the eastern branch in ancient times, but ancient Greek sources say nothing about this branch joining another river (i.e. the Nara, which the Sanghar course eventually joined further southeast). As for the western branch, its path can only be guessed at because there has been so much river activity in the area since then. The main city in the region, Patala, was located somewhere near the place where the two branches split. Its ruins have not been found, but if the Sanghar course does represent the eastern branch of the Indus from that time, then Patala may still be undisturbed and discoverable by archaeologists, somewhere northeast of Nawabshah on the edge of the desert, because this area has not experienced later river activity and sedimentation.

By the time of the Muslim conquest of Sindh in the early 8th century, the Indus was most likely following the Kandhkot, Khairpur, and then Shahdadpur courses from north to south. The present-day village of Dehat, on the Kandhkot course near Kandiaro, is probably the "Dahiayat" where the Muslim army crossed the Indus.

Around the early 1200s, there seems to have been a major shift in the course of the Indus. The reasons for this are uncertain. It could be because the Sutlej, previously an independent river flowing all the way to the sea, joined the Indus at this point, or it may have been because the two branches of the lower Indus converged at this point. In any case, the Indus now became wider, with bigger meanders and a more frequently shifting course. The river's course at this point was close to the Khangar and East Khairpur bluffs. It also now passed through the Sukkur gap, while whatever water channel flowed through the Aror gap ceased to be. Aror itself went into decline, while the island of Bukkur increased in importance. The shift to the Sukkur gap was complete by 1333 at the latest, when the river is described as flowing around both sides of Bukkur island.

Further south, the changes may have been more gradual. The Indus shifted to the Nasarpur Course, abandoning the Shahdadpur Course. Southeastern Sindh, previously watered by the Shahdadpur Course, became more arid and barren without its main water supply. Some water did still flow to the southeast from the Nasarpur Course via several spillways, most prominently the Western Puran and the Ren river. Around this period, the Soomra dynasty shifted its capital from Tharri, on the Shahdadpur Course, to Muhammad Tur, on the Gungro Branch of the Nasarpur Course. Finally, the area around Larkana became more fertile, and the Ghar Branch and Western Nara probably originated around this time.

In the following centuries, changes were more gradual. The river gradually shifted westward, away from the Khangar and Khairpur bluffs. This would have interrupted the offtakes to the Ghar and Western Nara, and human intervention must have taken place to maintain their courses. Further south, the river followed the Dadu course (west of the present course) to Sehwan. Accounts from the 1500s mention a branch of the Indus called the Sangra in Central Sindh, which is preserved as today's Sangra Wah canal. This would have formed the upper reaches of the West Puran and eventually flowing out to the sea. In Lower Sindh, Thatta became the main city in the 1300s; it was then an island between the Kalri and Baghar branches. The Gungro branch probably declined slowly, and was replaced as the main outlet stream by the Kalri by 1519 at the latest. The Kalri was itself later replaced by the Baghar.

The last major change in the Indus course was in 1758-9, when it shifted from the Nasarpur course to its present route flowing west of Hyderabad and Ganjo Takar. This, combined with dwindling flow from the Eastern Nara, caused southeastern Sindh to become even drier. In the delta, the main flow went through the Baghar branch until 1819, when it began to silt up. It then made its main course along the former Sattah branch for a ways, but at Chuharjamali it bent sharply to the west before reaching the sea at Keti Bandor on the Ochito branch.

Human history
The lower Indus valley was first populated by modern humans about 80,000 years ago. The Indus was then the route people took to first populate Tibet and Central Asia. (BETTER SOURCE?)

Ecology
On either side of the Indus there is a floodplain of varying width, between 5 and 160 km, known as the kacha area. This area extends from Mithankot down to the coast. Kacha lands are very fertile due to silt deposition during flooding. The situation changed significantly during the British Raj, when massive embankments up to 10 m high were constructed as part of an irrigation system. This now effectively channels floodwaters into this area, which mitigates flooding in the pucca areas outside the embankments but made humans and wildlife within the kacha area more vulnerable and requires them to migrate frequently.

Hierarchy
The Samarāṅgaṇasūtradhāra described the pura as the largest type of settlement, followed by the kheṭāka in the middle, and then the grāma as the smallest. The Aparājitapṛcchā has a different list: in descending order, pura, grāma, kheṭāka, kūṭa, and finally karvaṭa, with each one said to be half the size of the next one up (which Renu Thakur calls "a medieval version of the rank-size rule").

Pura
In ancient times, the word pura referred strictly to a fort. Over time, however, the word came to mean any town regardless of its particular functions.

The Mānasāra defined a pura as "a town furnished with orchards and gardens, with the dwellings of a varied population, frequented by buyers and sellers, and having the noise of trading-folk and the temples of seven gods".

The Aparājitapṛcchā uses the word pura in a specialized sense, to refer specifically to the king's largest town, in contrast with the nagara which was a feudal residence and headquarters of the nrpa.

Nagara
In early medieval South India, the term nagaram referred not just to the town but also to the town's merchants, merchant guilds, and town assembly.

Erivirapattanam
In South India, the term erivirapattanam was used to denote a fortified market town defended by merchant troops. Primarily located in remote and/or frontier areas, these towns functioned as entrepots and warehouses, and also as distribution centers for the surrounding rural and urban populations. The name erivirapattanam is evidently related to the word erivira, meaning "warriors who throw".

Bananujvattana
Primarily in Karnataka, the term bananjuvattana was used to refer to a large market town where merchants and merchant guilds formed a distinct governing body as part of the local administration. They shared administrative duties with other local bodies like the mahājana and were responsible for overseeing commercial matters and distribution of goods. This is in contrast to places like northern India, where the merchants participated in town councils as individuals, just like the other city residents, but did not form an official governing body.

Nigama
A nigama was a market center somewhere between a village and a full-fledged town.

Rajadhani
The word rajadhani generally referred to a capital city: the Mayamata distinguishes a rajadhani from a regular town by the presence of a royal palace, while the Samarāṅgaṇasūtradhāra describes it as a capital. The Mānasāra described the rajadhani as a riverside settlement with the king's palace in the middle, surrounded by the houses of the wealthy elite.