THIS is with reference to the report “Concerns raised over ‘poisoning’ of potable water in Thar” (April 5) related to the water quality data of samples collected from the coal blocks prepared by Dr Mark Chernaik of the Environmental Law Alliance Worldwide (ELAW). He published a report on how water quality data was interpreted, but the report lacks scientific rigour.

Thar has three layers of water aquifers. The top layer is shallow and dependent on rainwater. The water in this layer is less brackish and is used by the local people for drinking and agricultural purposes.

The second layer is between the shallow layer and the hard rock of the confined aquifer, which is the third layer. When it rains, the people of Thar enjoy sweet water from the shallow layer, but when there is no rain for an extended period, the water quality goes down. The samples in question were taken in June, right before Thar’s rainy season. This explains the said findings. Had the sample been taken throughout the year with at least 15-30 days between each sample, a more valid interpretation would have emerged.

The report did not even attempt a statistical analysis of the sampling, like, say, standard deviations and confidence intervals. Without statistical evidence, any research is non-scientific.

Besides, the report declares the water unsafe without any data regarding any ill effect on the health of the local people.

Prof (Dr) Zubair Ahmed US-Pakistan Centre for Advanced Studies in Water, Mehran University of Engineering and Technology
Jamshoro

Published in Dawn, May 4th, 2023