The coastal region of Bangladesh covers 20% of total land of Bangladesh with 711 km long coastline. The coastal zone of Bangladesh consists of Bagerhat,Barguna, Barisal, Bhola, Chandpur, Chittagong, Cox’sBazar, Feni, Gopalganj, Jessore, Jhalkati, Lakshmipur, Narail, Noakhali, Patuakhali, Pirojpur, Satkhira andShariatpur District. The coastal line areas are considered as the most vulnerable area in respect of safe drinking water. Groundwater practice for the coastal area is uncertain. The easily accessed aquifers are extremely saline affected. More than 10 million people are fighting against the same challenge. Though some aquifer depth of 300 to 400 meter is suitable, it is not adequate for the large number of people. Due to the impact of climate change, frequent storm surge events affect sweet water ponds and shallow tube wells.Having surface water without any treatment is not hygienic to drink. Government, local NGOs and international NGOs implemented different types of system for using surface water like pond sand filter (PSF), desalination system, Carocell and so on. As the system needs skilled people to operate, the system becomes inactive after a certain period. So it is a matter of regret that both options of ground water and surface water are almost inactive to meet the drinking water demand in the coastal area in Bangladesh. Even in the dry season, there is serious scarcity of sweet surface water source. Sometimes they used to go more than 5 km for collecting drinking water only. Most of the coastal villagers are fishermen and farmers. They are not capable of paying for bottled water. Only one option is remaining, that is rainwater. Rainwater harvesting is the most primitive practice in Bangladesh. It is considered as an alternative water source in Bangladesh.
In the monsoon period of June to October, heavy rainfall occurs in Bangladesh. Bangladesh is also a tropical country. The highest rainfall occurs in some coastal district of Bangladesh. The coastal districts receive more than or equal 2700 mm rainfall per year. According to the information of Bangladesh Bureau of Statistics (BBS, 1997) 1.95 – 2.80 m3 of rainwater was available per square meter of catchment area each year for development of rainwater based water supply system. Rainwater harvesting for drinking purpose is common practice in rural area but its access is in limited scale. 36 percent of people in the coastal belt depend on rainwater only because they have no alternative options remaining. However, the protected ponds are replenished by rainwater each year are another significant source of highly saline prone area. However, rainwater water is relatively good. The rain water is free from arsenic contamination, salinity and other harmful infectious organisms and pathogens. Beside this the physical, chemical and bacteriological characteristics of harvested rainwater represent a suitable and acceptable means of potable water. Though it is not free from toxic impurities but it is easily avoidable. But the harvested rainwater quality may be affected due to long time storage. Bacteriological contamination like coliform can happen if the catchment is not properly cleaned. The first run off from the roof should be discarded to prevent entry of impurities from the roof. If the storage tank is clean, the bacteria or parasites carried with the flowing rainwater will tend to die off. Nowadays rain water harvesting refers to both large (community) and small (household) scale. A simple affordable, technically feasible and socially acceptable safe drinking water supply system in thecoastal rural area is very much in demand. In this circumstance, rainwater harvesting system can be considered as a probable solution of the drinking water problem in the arsenic and salinity affected areas.
In the present context, all main water supplies have converted and the alternative option of rainwater has taken place the main option to fulfill the drinking water demand.
Aminul Islam Sohan
International Correspondent,Association of Life Science and Engineering Writers (ALSEW)
Lecturer, Department of Civil Engineering, Mogadishu University, Somalia
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