Reducing dependence on groundwater

That the Water and Sewerage Authority (WASA) of Dhaka has been under pressure for reducing dependence on underground water is quite obvious. Now the managing director of the organisation makes it public at a discussion titled 'Water of Bangladesh and drainage management: problem and solution' held recently at the Jackson's Height in New York. The WASA's target is to reduce the city's dependence on underground water  to 30 per cent by 2020 from its current 78 per cent. Depletion of groundwater has long been a cause for serious concern here. According to a study by the Groundwater Monitoring Survey Report of the Bangladesh Agricultural Development Corporation (BADC) and the Institute of Water Modelling (IWM), the city's water table is falling by three metres a year. The water level has receded by as much as 50 metres over the past 40 years to 65 metres below the ground. All this speaks volumes for the precariousness of the situation. The fall in the water table has only made the city's infrastructure more vulnerable than it would have been in case of an earthquake.   
The key question now is, how the WASA proposes to carry out its plan for reducing dependence on groundwater. Options are not many. Either it will have to use surface water or harvest rainwater for the purpose. Effective rainwater harvesting (RWH) systems, according to the survey report, could meet 15 per cent of Dhaka City's need for water. Currently, there is a shortage of water by 500 million litres a day. A 15 per cent supply at moderate cost is quite a welcome move. Its merit lies in the fact that rainwater does not require treatment and can remain bacteria-free for five to six months. Another plus point is that its storage will not be limited to any select or privileged groups of citizens. What is therefore needed is to develop a simple and effective technology for rainwater conservation. Even if this is done, the issue of recharging the groundwater should be kept in the priority list or else there will be a potential threat to supplant the underground with saline water in course of time.
For sometimes the authorities have been toying with the idea of bringing water from the river Meghna for treatment before supplying to homes and offices. It is not impossible but quite a costly venture by all counts. As the rivers girdling the city are heavily polluted, their waters cannot be used for treatment purposes. It is because of this pollution, the Meghna has been considered a source for water withdrawal. Desperation may force the authorities to go for this venture but a programme should as well be undertaken for gradually making the four rivers around the city pollution-free. It will make the city better off.