The Gangetic Delta is an extensive tract of cultivated and forest-covered country, composed of alluvial or transported soil brought down the country by the Ganges and Brahmaputra rivers and their numerous tributaries, the water-sweep ings of two basins whose aggregate area is 432,480 square miles. The Delta is intersected from north to south by many broad rivers, and by endless creeks running one into the other, filled for the most part with salt water when near the sea. This tract of land occupies approximately 28,080 square miles of superficial area, or double the area of the Delta of the Nile. Measuring from west to east, or from the right bank of the Hoogly river opposite to the Saugor tripod on the south west point of Saugor Island, to Chittagong, it is 270 miles in width, presenting to the Bay of Bengal a series of low, flat raud-banks, covered at high water and dry at low water. A few miles from low-water mark commence mangrove swamps; a little further inland, trees appear, and lastly cultivation,—the nearest cultivation in the central portion of the Delta being 47 railes from the sea. In the sea front of the Delta there are nine prin cipal openings having a head stream, that is, having water flowing direct from the Ganges, or from the Megna or Brahmaputra. They are- 1, the Ganges ; 2, the Megna or Brahmaputra ; 3, Horinghatta ; 4, Pussur ; 5, Murjatta or Kagga ; 6, Barapunga ; 7, Mollinchew ; 8, Roymungul or Juboona. ; 9, Hoogly. Besides these large rivers, there are numerous openings having no head stream, being mere salt-water tidal estuaries. These openings or headless rivers are the deepest, as no silt or deposit is poured into them from the higher lands. The tides in the Hoogly run with a rapidity in the springs of seven miles an hour, between Sanger and Calcutta. At Calcutta it is high water about 2 hours 30 minutes on full and change of the moon. The bore is of not unfrequent occurrence in this river.
This river's annual rise begins in the end of April, and continues to increase till the middle of August, when it reaches in many places 32 feet, and the level districts in its lower course are inundated. At Benares, after the Ganges has received the waters of its tributaries, the Kali Naddi, the Gumti, and others, the breadth varies from 1500 to 3000 feet ; the average discharge each second of the year has been estimated at 250,000 cubic feet.
By the latter end of July, all the lower parts of Bengal contiguous to its banks are overfloWed, forming inundations of a hundred miles in width, where little appears above the surface of the flood save isolated villages and trees. Barks of every
kind then steer a direct course, husbandry and grazing are alike suspended, and the peasant sculls his boat across the fields. In some parts of Bengal, whole villages are every now and then swept away by changes in its course, through districts from which, a few years before, it was several miles distant.
The Bhagirathi, Jalangi, and Matabhanga, are all offshoots of the Ganges, which unite to make up the headwaters of the Hoogly. In former times, the main volume of the Ganges was carried to the sea by one or other of these channels, but they now receive so little water as only to be navigable in the rainy season, and then with difficulty. Since the beginning of the pre sent century, Government has undertaken the task of preventing these Hoogly headwaters from further deterioration. A staff of engineers is constantly employed to watch the shifting bed, to assist the scouring action of the current, and to advertise the trading community of the depth of water from time to time. In the year 1877-78, a total sum of 9522 was expended on this account, while an income of i.32,494 was derived from tolls.
The Ganges river basin embraces 391,100 square miles. Average discharge at Hardwar, when the river is at its lowest, 7000 cubic feet per second ; at Rajmahal, a high flood discharge of 1,800,000 cubic feet per second, and an ordinary discharge of 207,000 cubic feet. The Ganges during its minimum discharge at the Bhagirathi head in April has a breadth of surface of 2800 feet, an average depth of 15 feet, its sectional area 42,000 square feet ; and multiplying this with its mean velocity of 1-92, gives its discharge per second as 80,660 cubic feet. During the inundation the breadth of surface is 10,633 feet, average depth 30 feet, sectional area 318,990 square feet, mean velocity 4.25 = 1,355,707 cubic feet discharge per second.
The Ganges near the delta has frequently altered its course. Colonel Colebrooke mentions that, between 1779 and 1788 such an alteration had occurred at Colgong, making a new channel 90 feet deep, above which the earth rose 25 feet, a removal of 115 feet of earth. Entire fields at times are hurled into the river, and large islands disappear rapidly when the power of the main cur rent is made to bear on them. Budh-Ganga, also Burha Ganga, is an old bed of the Ganges trace able below Hastinapur, Soron, and Kampil.— Hooker, Him. Tour. ; .Himalaya, Cal.
Rev. ; Royal Sanitary Commission Rep. ; G az.