Addressing fresh water scarcity in coastal zone
Salinity infrusion in coastal areas is a natural consequence of flooding.
Fresh water scarcity is an increasing problem in the coastal zone of Bangladesh as it is turning into brackish and saline water gradually. Climate change exacerbates the problem through sea level rise, poor rainfall in winter, high rate of evaporation and cyclone and storm surge. Some human induced interventions like barrage in the upstream rivers to diversify the flow, faulty management of coastal polders and commercial shrimp culture and salt production have increased the salinity level of surface water many-folds. Higher saline concentration in the surface water compels coastal people to depend more on ground water. Therefore, the ground water extraction for drinking and irrigation purpose has been accelerated. However, the water of shallow aquifer is also being contaminated by salinity intrusion. So, deep tubewell is the ultimate source of fresh drinking water for most of the cases. Nevertheless, the deep tubewell is costly to construct and therefore, it is quite often beyond the affordability of poor households. As the source of fresh drinking water in terms of deep tubewell water is far distant from poor households the children and women of those households need to spend a quality time to collect water. It has been found that quite often the poor households depend on sources of water adjacent to their homestead either from surface water or shallow tube well for drinking purpose and suffer from diseases derived from saline containing water. The salinity problem is more acute in the dry season when there is a less precipitation which is not adequate enough to leach salinity from soil naturally and dilute the concentration of salinity from surface water. As an alternative source of fresh water, rain water harvesting is a common method in the coastal areas in Bangladesh. Number of NGOs has already put intervention in this regard. One of the most common methods of rain water harvesting is collecting the water into pond and purify it by pond sand filter method for making it safe for drinking. Apart from that, collecting water from rooftop into storage tank is also a popular method. However, collecting water into storage tank only provides fresh water for a certain period (approximately 3 to 4 months) and the water holding capacity of the storage tank is most of the cases is very limited. But if rain water can be collected in open well from the roof top the benefit can be both short and long term. In short term impact people can use a huge volume of harvested water as the water holding capacity of such a well is much higher than the conventional storage tank and in long term it is likely to recharge ground water aquifer in terms of diluting or replacing saline water. “Harvesting rainwater and injecting into open well” could be a feasible method of alternative source of fresh water not only in the coastal Bangladesh but also for the drought prone and arsenic effected areas in Bangladesh. It is a cost effective method and has been utilised largely by “Participatory Learning and Action Network” Kerala, India. However, there is no significant method under practice to combat salinity problem and ensure safe drinking water in dry season in coastal Bangladesh, although the salinity problem is more acute in winter when there is low flow condition prevailing in river water and is not sufficient enough to counter the salinity ingression into it. The writer explores the method of desalinisation of surface water, which is a very simple laboratory method, but can put a magnificent corrective impact on coastal Bangladesh. The method is to put a container in the middle of a bigger one and cover them with a paper which can trap heat (like foil paper or cling film), keeping in mind that there should be no gap between the paper and the bigger container. Then to keep a small weight in the middle of the paper so the water can be trickled down to the smaller container, keeping the whole system in the sunniest place in the surrounding of one's homestead or at the roof top. The method is cost effective as it comprises natural evaporation and condensation method. This method has also some commercial benefit. If it is practiced in a small scale at household level, the salt produced in the large tank during the evaporation can be used for household cooking and if it is practiced in a large scale the salt produced may bring commercial benefit. Access to safe drinking water is one of the basic human rights. However, salinity intrusion in the coastal zone has already limited the accessibility of people to safe drinking water. Moreover, the coastal area under salinity coverage is likely to be increased in the upcoming years due to climate change. Therefore, to ensure safe drinking water by creating alternative sources in the coastal zone should be the top priority of the government, NGOs, scientists and other stakeholders.
For all latest news, follow The Daily Star's Google News channel.
Comments