From the Indus nine canals lead, two of them excavated by the British ; and in July and August the Indus floods the face of the country, the waters reuniting to run into the eastern Narra, a great channel belonging to the Sind system of irrigation.
In the Bari Doab, between the Beas and Ravi rivers, there has been a great State canal com pleted; but canals are still needed for the 7,000,000 of acres unirrigated in the Rechna Doab, between the Ravi and Chenab ; the Chuch Doab, between the Chenab and Jhelum ; and the Sind Sagor Doab, between the Jhelum and the Indus.
That of the Bari Doab up to 1871-72 cost upwards of £2,000,000, and was irrigating 300,000 acres.
The great Sirhind Canal, commenced in 1871 72, was projected to draw its waters from the Suttlej, to irrigate an immense area now desert, and the total cost was estimated at £2,980,427, a third part of which was to be borne by the native states.
After the rivers of the Panjab unite at Mithan kot, the Indus flows for 450 miles to the sea, through the arid rainless country of Sind. Here artificial irrigation is essential to cultivation. The river during bygone ages has silted up, and its banks are now greatly above the alluvial plain. When the bed attains a certain height the water falls over, and since historical times the river has been changing its course to the west. The banks are permanent only at Sukkur ; at Jharrak, where it is bound by rocky banks ; and at Kotri, by hills and deep tenacious clayey soil. The canals are excavations carried away from the river in an oblique direction, so as to secure as great a fall as possible. They vary from 10 to 100 feet in width, and from 4 to 10 feet in depth, and none are deep enough to draw off water from the river except during inundations. The irrigation is carried on by the water flowing into the channels during the inundations, or it is raised by the aid of machinery or Persian wheels. Some of the canals are 70 and 80 miles long. On the western or right bank, the chief canals are the Sind, 66i miles, Ghar or Lar khana, Bigari, and Western Narra.
On the east or left bank of the Indus river is the Eastern Narra. It was an ancient channel •which passed through the Thur, and had near it among the sand-hills, about 400 'small dunds or lakes or bottoms. In 1859 a channel from the river at Rori was led into it, and its channel was dammed at places to prevent the escape of water into the large dunds.
Two canals have been led from the Eastern Narra,—the Mitrau, which in 1866 had 190 miles open, and irrigated 156,803 acres, and the Thur canal, irrigating 38,000 acres. Under Sir Bartle Frere's administration, the ancient channel of the Narra, 120 miles long, was reopened on the 7th May 1867, to distribute water over the vast plain of Mirpur.
From Hyderabad southwards, the Fullali canal is the main feeder of irrigation channels. Origin ally it was a natural branch of the Indus, which it rejoined 16 miles below Hyderabad ; this was stopped by a dam in the time of the Amirs, and its waters were sent into the Gaja, the Guui, and other canals.
In 1861 the cost of clearances of the main canals was £41,041, but the allotment in 1871-72 was insufficient. Canals of a permanent character, proposed to be led off the Indus from Sunni., Jharak, and Kotri ; and the first of these, from Sukkur, was opened in 1870.
In the valley of the Ganges, above its junction with the Jumna at Allahabad, and in the whole length of the country through which the Jumna flows, the rainfall does not exceed 30 inches. Firoz Shah, emperor of Dehli between 1351 and 1388, drew a canal from the Jumna to water his favourite hunting ground at Hissar, but it had long fallen into disrepair, when Akhar in 1568 ordered its restoration. In 1626, Shah Jahan's engineer, Ali Murdan Khan, projected a canal in the Doab, which shortly ceased to flow. He also led one from that of Firoz, to convey water to the city of Dehli. The Dehli canal crossed the low land by a masonry aqueduct, traversed the Aravalli hills by a canal cut through the solid rock, 60 feet deep at the crest, and flowed through the city in a masonry bed, throwing off innumerable minor streams ; but in 1753 this branch ceased to flow. When the British came into possession, all these works had fallen into ruin, and in 1820 the canal of Firoz was restored from where the Jumna issues from the Siwalik hills. At Dehli it separates into a branch which enters the city at the Kabul gate, and part of it flows down the Chandni Chouk ; the other branch follows that of Firoz to Hissar, and sends off the Rolitak branch. The united length is 445 miles, and that of the watercourses 728 miles ; and the total outlay up to 1871-72 was £282,517, from about 447,171 acres.