Soil and Water Resources of Sundarbans

The people of the Sundarbans, spread over India and Bangladesh, depend mainly on agriculture, the productivity of which is low due to several constraints related to soil and water resources. The soils of the Sundarbans region are generally occupying deltaic geomorphic position and have developed on alluvium. The soils are affected by salinity, while acid sulphate soils having pH <4 are also found in patches in the region. Soils are generally low in available N and organic carbon, low to high in available P, and high in available K. The soils are usually well-supplied with micronutrients, except Zn. Acid sulphate soils are deficient in P, and very high in water soluble Fe, Al, and Mn. Rivers are all tidally fed as these rivers have lost their upstream connections with the Ganges due to heavy siltation and solid waste disposal. This region experiences significant long-term variation in quality of river water, such as the surface water temperature, salinity, pH, dissolved oxygen. The salinity of river water increases gradually from post-monsoon to pre-monsoon period and thereafter decreases to a lowest value in monsoon, and the cycle repeats annually. The top saline water bearing aquifers are generally separated from the underlying fresh water group of aquifers by a thick impermeable clay layer. The arsenic contamination problem in groundwater has been reported in the Sundarbans. In general, there is seasonal fluctuation of salinity in the groundwater too, salinity is higher in dry season than in monsoon.