Groundwater depletion in dry season is very common in Bangladesh; but plenty of rainfall in wet season and thus surface run off.
Each situation has to consider many factors, but if quality groundwaters are needed for drinking, it is a shame to alter groundwaters by recharging artificially with stormwater. But you could retain stormwaters, pretreat them in various ways to drinking water standards before injecting. If you have reasons why waters are abnormally running off rather than being absorbed to replenish groundwaters, such as if you have gullies, impervious surfaces, areas that were once forests, and are now barren, channelized streams that have lost floodplain connectivity, there may be opportunities to restore hydrology. Questions like what are the natural and current groundwater pathways, what changes have been made? Should stormwaters be stored in dams, reduced by restoring natural hydrologic processes that encourage natural infiltration? And is there ways to inject water safely, how best to do economically, while not damaging groundwaters beyond their needs for present and future.
William F Hansen your every word is correct. But the problem of Bangladesh-soil is that, the top-most layer is impervious clay. So the opening of the aquifer has to be identified very carefully. In addition many parts of ground water of Bangladesh is contaminated with arsenic. So my suggestion is
1. Harvest rain water
2. Give it treatment to reach safe level
3. Consume or use it directly
4. Decrease dependency on groundwater
5. Clean and restore the surface water bodies
6. Make arrangements for resting water at the opening of aquifer
7. Let nature to recharge the groundwater table with its sustainable sieve action
Dear All,
Thanks a lot for important points. It is really better to restore nature by the natural processes.
Yes, it is wise to recharge groundwater. But quality of water used for recharging should be good. Also one should ensure that the recharged water is not being stored in the zone of contaminated water such as arsenic water which is reported from many places, The storing zone should be free from any kind of contamination.
Dr Rai,
Thanks for your comments; but how we can get contaminated free zone. A lot of people in Bangladesh and we are polluting most places in different ways.
Dear Dr. Biswas
Geometrical shape of the recharging zone can be mapped by geophysical electrical methos such as Electrical resistivity tomography , For example see my papers published in Current Science, 105(10), 1410-1418, 2013; Current Science, 102(1), 61-69, 2012; Jour. of Indian Geophysical Union, 19(3), 256-269, 2015. Quality can be tested depth wise by analysing water samples.
Dr. Rai,
Thanks for your information. I will try to download those papers.
Going by the earlier descriptions / comments on the groundwater scenario, it appears that artificial recharge is one of the solutions to tie over the water scarcity, even for domestic purposes, in Bangldesh. One of the main guidelines in artificial groundwater recharge practices is that the quality of water used for artificial recharge should be better or equivalent to the regional groundwater quality. If that is the case, then there need not be any worry for groundwater quality deterioration due to artificial recharge practices.
I doubt that the entire top soil in Bangladesh is impervious, in that case what is the recharge source of groundwater ?? It may not be entirely so, hence identifying suitable recharge sites.
If direct well recharge is practiced, then as suggested by Dr. William, the rain water has to be filtered before letting the water directly to the well. In my opinion, if the top soil is clay mixed, then direct well recharge is a better option, than spreading on-land methods.
In a water scarce area, it is also advisable to go for roof-top rain water harvesting, collecting directly the rain water in some tanks for direct consumption/use. However the rain water has to go through a filtering mechanism, before the collection.
It may be noted that by artificial recharge practices, the problem of Arsenic contamination gets reduced.
As a long term measure, reducing the dependence on ground water and going for surface water conservation methods such as reservoirs or check dams are a better option.
There is always a possibility that any clean water you use for recharge will be contaminated by someone or something else. I thought you wanted to recharge ground water for some geological purposes, but if you want to store it as a drinking water, maybe it would be better to keep at least part of it not "in the ground" but in some controlled reservoirs.
Albeit, the source water used for recharging purposes is free from silt, both source water and groundwater should undergo chemical and bacteriological analysis in order to ensure the (nearly) contaminant free artificial groundwater recharge.
If required, the intensity of salinity ingress can be investigated using geophysical studies. (Problems such as water-logging and soil salinity can be averted, if the top soil extending over first few meters from the ground surface - be averted for recharging purposes).
Both low-permeability (suppressed recharge rate) and high-permeability (loss of recharged water by draining) units should be averted for recharging purposes.
If the physical processes (cause) associated with the artificial groundwater recharge are taken care, then, the resulting chemical processes (effect), i.e., the water-quality would automatically be taken care.
Suresh Kumar.
http://www.doe.iitm.ac.in/gskumar/
Thank you all for good points. Need dictates us to do many things at the cost of even environment.
We are dumping industrial pollutes without any treatment, mixing freely with rain and river water. Nearby Dhaka, capital of Bangtladesh, is contaminated up to second phase of ground water making it unsuitable when pumped out by hand tubewel. Greed and lack of knowledge making the environment more unhealthy.
Artificial recharging is good but with good quality of water such as rain water from roof top or accumulated in pond. Other sources of water such as domestic and industrial used water should be used only after proper treatment. Such water preferable should be used for irrigation or again for industry purposes.
I appreciate Sekar and Rai. It is better to recycle water rather artificial recharging, especially in Indian sub-continent. In most cases we destroy natural habitats by not following environmental safety guidelines.
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