Monday, April 18, 2011

Some random thoughts on floods and water quality

I have been wanting to write something on floods and water quality since our Orchard Road floods make headline news in June 2010. But other committments in life came to the fore and this task became relegated to the background.

Brisbane floods: Up close (18 Jan 2011, ABC News)

Figure 1: This looks like some sort of water treatment or wastewater treatment plant in an industrial area
Figure: Same area as Figure 1 after the flood. Notice that the treatment plant is overwhelmed. If it is a water treatment plant supplying tap water, you can expect contaminants from the flood to go into tap water. If it is a wastewater treatment plant, you can expect untreated or partially treated wastewater to be carried by the flood to who knows where. Depending on the type of wastewater, contaminants can include raw sewage, industrial effluent (heavy metals, solvents etc.) or agricultural waste (animal waste, pesticides, fertilisers etc.).

Orchard Road Floods Straits Times/ Stomp (June 2010)

Figures: The same principle applies here. We had a flood. Flood washed everything around Orchard Road in its path. Let me hazard a guess - "everything" should include motor oil/ fuel (from vehicles), rubbish (glass, paper, aluminium), animal waste (stray animals, rats), pesticides/ fertilisers (lawns, green spaces) and lots of sediment (notice the "kopi susu"-like flood water). Where do you think the flood water eventually end up? Orchard Road is part of the Marina Reservoir watershed so yes, the contaminants end up in our reservoir. Our water treatment plants are supposed to be very effective so most of these stuff should be removed before reaching our taps. Even if this were true, treatment costs will likely rise from an increase in wear and tear of the treatment units handling such a heavy and diverse load of contaminants.

Figure: Tsunami caused by earthquake in Japan (Mar 2011) ( The same can be said of a tsunami. It can carry everything nasty land pollutant in its path far inland, impacting water supplies and wastewater processing. I remember first learning about this term "tsunami" in secondary school geography. It didn't strike a chord with me then. Perhaps there weren't that many tsunamis then. But nowadays, even children know about this term when everyone can see horrific images of death and destruction following its wake. It has also receive much publicity since the tragic Asian tsunami in Dec 2004.

A disaster may be split into 2 phases with respect to its damage. The 1st phase is the disaster itself. Energy from an earthquake or flood causes loss of life and property. This phase usually lasts a short while (though there are floods that take months to recede). The second phase comes in when the population starts to rebuild their lives. The economy is torn to pieces. Food, water and fuel become scarce. Ditto for daily necessities. If law enforcement is weak and the people desperate, social disorder ensues. Without clean water (and food) and proper sanitation, people start coming down with water borne diseases which may spread without check, especially when people are herded into cramped refugee camps. See my earlier post for a fuller discussion on the aftermath of a disaster.

No comments: