Rivers and Lakes

Rivers are a prominent and important feature of the landscape in Bangladesh. Some rivers are known by different names in various portions of their course. The Ganges (Ganga), for example, is known as the Padma below the point where it is joined by the Jamuna River, the name given to the lowermost portion of the main channel of the Brahmaputra. The combined stream is then called the Meghna below its confluence with a much smaller tributary of the same name. In the dry season the numerous deltaic distributaries that lace the terrain may be several kilometers wide as they near the Bay of Bengal, whereas at the height of the summer monsoon season they coalesce into an extremely broad expanse of silt-laden water. In much of the delta, therefore, homes must be constructed on earthen platforms or embankments high enough to remain above the level of all but the highest floods. In non-monsoon months the exposed ground is pocked with water-filled borrow pits, or tanks, from which the mud for the embankments was excavated. These tanks are a chief source of water for drinking, bathing, and small-scale irrigation.

Climate

The climate of Bangladesh is of the tropical monsoon variety. In all areas about 80 per cent of the annual rainfall typically occurs in the monsoon period, which lasts from late May to mid-October. Mean annual precipitation ranges from about 1400 mm (about 55 in) along the country's east central border to more than 5080 mm (200 in) in the far northeast. In addition to the normal monsoonal rainfall, Bangladesh is subject to devastating cyclones, originating over the Bay of Bengal, in the periods of April to May and September to November. Often accompanied by surging waves, these storms can cause great damage and loss of life. The cyclone of November 1970, in which about 500,000 lives were lost in Bangladesh, was one of the worst natural disasters of the 20th century. Bangladesh has warm temperatures throughout the year, with relatively little variation from month to month. January tends to be the coolest month and May the warmest. In Dhaka the average January temperature is about 19° C (about 66° F), and the average May temperature is about 29° C (about 84° F).

Vegetation and Animal Life

With the exception of the Chittagong Hill Tracts, portions of the Madhupur Tract, and the Sundarbans (a great tidal mangrove swamp in the southwestern corner of the country), few extensive forests remain in Bangladesh, the wooded area amounting to less than one-sixth of the total area. Broadleaf evergreen species characterise the hilly regions, and deciduous trees, such as acacia and banyan, are common in the drier plains areas. Commercially valuable trees in Bangladesh include sundari (hence the name Sundarbans), gewa, sal (mainly growing in the Madhupur Tract), and garyan (in the Chittagong Hill Tracts). Village groves abound in fruit trees (mango and jackfruit, for instance) and date and areca (betel) palms. The country also has many varieties of bamboo. Bangladesh is rich in fauna, including nearly 250 indigenous species of mammals, 750 types of birds, 150 kinds of reptiles and amphibians, and 200 varieties of marine and freshwater fish. The rhesus monkey is common, and gibbons and lemurs are also found. The Sundarbans area is one of the principal remaining domains of the Bengal tiger, and herds of elephants and many leopards inhabit the Chittagong Hill Tracts. Other animals living in Bangladesh include mongoose, jackal, Bengal fox, wild boar, parakeet, kingfisher, vulture, and swamp crocodile.

Mineral Resources

The mineral endowment of Bangladesh is meager. The principal energy resource, natural gas, is found in several small fields in the northeast. There is a coalfield in the northwest and large peat beds underlie most of the delta. Limestone and pottery clays are found in the northeast.