The effect of saline water intrusion is highly seasonal in Bangladesh. Saline water intrusion is minimum as the salinity front in estuarine and floodplains greatly push back during the monsoon (June-September) when the rivers discharge about 80 percent of the annual fresh water flow. The majority of coastal soils are non-saline in the rainy season. From December onwards due to the reduction of fresh water flows allow increasing levels of estuarine salt-water penetration inland. Saline waters penetrate up to 130 kIn inland in the lower Meghna and up to 290 km up the Passur River in the South West of the country (Nishat, 1988). Maximum Salinity levels occur during March-April.

Withdrawal and diversion of water from the Ganges at Farakka during the dry season reduced drastically the fresh water flow. Lower river flow from upstream increasing the pushing effect of saline water from the sea is the main cause of increasing salinization in deltaic regions of Bangladesh.

In Khulna and Patuakhali districts 60-70 percent of arable land is affected by salinity in the dry period. While about 15 percent of the arable land of Barisal, Noakhali and Chittagong districts are saline. Figure-2.l0 presents the Salinity in ground water table of Bangladesh.

The vast coastal croplands suffer from salinity related problems in the winter months. This is particularly common in nearly 1.0 mha of the present salt affected soil in the coast. Because of cyclone and storm surges, high spring tide inundation and capil1ary actions salt accumulate at the surface and root zones. As a result, a large area in the coastal districts is virtually unsuitable for a number of crops, while the production of other crops is less due to salt injury. About 0.13 Mt food grain is lost at present annually due to adverse impact of soil salinity. Climate change effect will be severe in the coastal region. Preliminary investigation reveals that the area of salinity has extended up to 3.05 mha covering the districts of Chandpur, Magura etc.

Groundwater is crucial for agriculture, drinking water and industrial use. Main source of potable water is ground water in the coastal zone because of high surface water salinity. There are both shallow and deep aquifers beneath the coast, separated by thick clay layers (Nishat, 1988). Shallow aquifer salinity levels and depths are extremely variable within short distances. In contrast, the deep aquifer is regionally continuous and its salinity levels relatively uniform. The saline/freshwater boundary of the deep aquifer is close to the coast, except in the far west where the boundary is 120-160 km inland.