In the past there had been a secular decline in surface water availability in the north and south western part of Bangladesh sometimes called ‘moribund delta’, as tributaries of the Ganges in the north and distributaries in the south began to silted up. The process was
accelerated by the upstream of diversion of water from the river system for consumptive and non consumptive uses. The reduced availability of surface water in the region adversely affected the normal recharge of the ground water table in a number of areas. A smaller surface water run off also impacts on salinity level in the coastal areas. For example: in Khulna area during the dry season of the 1990s salinity line moved further inland.
The surface water quality is affected by untreated industrial effluents, Municipal waste water and run off from the surface of the agricultural lands treated with pesticides and chemical fertilizers. Pollution problems in the rivers close to the industrial areas are exceedingly high. For example: The dissolved oxygen (DO) level in the Buriganga has been found to be very low, and hence toxic. The Sitalakhya, Turag and Balu are also highly polluted. The water quality in Dhaka is so poor that the Environment Department of Bangladesh in a report said that “the water from surrounding rivers can no longer be considered as a supply source for human consumption.
Unlike Chittagong and a number of lesser urban centres, the requirement of potable water in the city of Dhaka is met entirely by groundwater abstraction. Excessive abstraction under pressures of increasingly larger population may further lower the ground water table and expose certain areas to serious scarcity and even land subsidence. The possibility of such a danger has to be seriously investigated. In any event the use of surface water as an important source of drinking water in the city of Dhaka brooks no further delay.
The levels of arsenic contents in the ground water is of major concern in Bangladesh. Prolonged use of water with arsenic concentration above the nationally recommended maximum of 0.05mg/ 1 for drinking purposes may pose serious hazards. The problem has assumed a serious dimension in specific areas in the south – west and south- east regions. The seriously affected areas are around Chandpur. According to an estimate about 20 million people drink water exceeding the safe arsenic level.
