Salinity in groundwater: Find alternatives to prevent fish disease

High salinity concentration in the waters of southern districts of the country was a matter of concern for long. The onrush of brackish seawater could be decreased by the fresh water from upstream. The salinity concentration was within a bearable limit as there were no dams in the rivers. But the flow of water has dipped due to the dams in the upstream in recent times. The people of the southern region have been living in an unbearable condition.

Amid this crisis, a news report on rising salinity concentration in the groundwater of northern districts has intensified the worries. The reason for this high concentration of salinity in the water is the use of salt in fish farming in ponds, finds a recent study of the Bangladesh Water Development Board (BWDB).

The water, soil and the environment experts dubbed this finding of high concentration of salinity in the northern districts’ groundwater far away from the coastal areas as “surprising” and “dangerous”.  They think this salinity could widely affect the lives of the people of the areas including their potable water supply and agriculture.

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According to a Prothom Alo report, the study was conducted on water samples collected from 100-feet depth of the ground near 49 ponds in six upazilas. Measuring the electrical conductivity (EC) is the general method of ascertaining the salinity concentration in soil, with the EC reading increases if the salinity is high. As per the Bangladesh standard, if the EC remains within 2,000 microsiemens per centimetre water, it is potable, while the range for irrigation water is 3,000 microsiemens.

Though no samples collected from the areas near 49 ponds crossed the 2,000 microsiemens ceiling, those were found to be doubled or tripled from their previous reading of 200-300 microsiemens.

The groundwater samples were collected from nearby areas of ponds where salt is being used for a long period of time, from ponds where salt use is a recent phenomena and from ponds where no salt is used. The study revealed that salinity concentration is higher in samples collected from the nearby areas of ponds where salt is being used for long.

Speaking about this, hydrology expert professor Mujibur Rahman said the study has made them aware of a completely new kind of danger appearing in nature. If this trend of salinity rising continues, this could create a crisis in the northern districts where people are facing scarcity of water. This could also affect crop production.

Chief scientific officer of Khulna divisional office of Soil Resource Development Institute (SRDI) GM Mostafizur Rahman said salinity could spread through osmosis or through spill over of ponds during the floods.

We have destroyed crop fields through shrimp cultivation in brackish water in the southern districts. Now we cannot endanger the agricultural activities in the northern regions by using a huge amount of salt in the name of fish farming in ponds.

Use of salt in fish farming must be stopped if salinity concentration in the groundwater intensifies due to this practice. It is by no means warranted that agriculture and the environment be destroyed due to salinity of water in the north like that of the south. Alternative methods have to be found to prevent fish diseases in northern areas. Salt cannot be used for that.

We can use the experience of other countries in this case.