GLOBAL WARMING’S IRONY: More floods but less freshwater supply

Dr. Thian Yew Gan (inset), a professor of civil and environmental engineering, warns of more flood but short freshwater supply amid the onslaught of global warming. (Jennifer P. Rendon)

By: Jennifer P. Rendon

The devastating flood that hit Venice in Italy is likely to happen in Philippine cities.

And as the world braces for global warming, expect more flooding to happen. But here is the cruel irony: expect long-term freshwater supply shortage.

Dr. Thian Yew Gan made this warning as he discussed “Perspectives on Multi-facet Impacts of Global Warming on Earth’s Waters” during a lecture-forum at the University of the Philippines Visayas on Nov. 19, 2019.

Gan is a professor of civil and environmental engineering of the University of Alberta specializing in water resources, hydrology, cryosphere, remote sensing, and environmental impact of climate change.

“The problem is you can have more rainfall but you have less stream flow,” he said.

Gan, who is married to Ilongga engineer Esther Gan, has been giving lectures in different parts of the world such as Asia, Europe, and North America.

The UP Visayas lecture was his first in the Philippines.

By sharing his perspectives on climate change impact, Gan hopes to raise awareness, especially to the younger generations.

During the lecture, he presented several slide shows and scientific evidences on the impact of global warming and why these changes have been occurring.

Global warming is the long-term rise in the average temperature of the Earth’s climate system. It is a major aspect of climate change, and has been demonstrated by direct temperature measurements and by measurements of various effects of the warming.

Gan said that green house effect plays a key role in all those changes.

He cited as examples the melting of glaciers and of sea ice that has never happened before in a very significant way.

“All those things have not happened in a thousand of years in the past and has started to occur in recent years,” he said.

Based on instrumental temperature record, 2016 was the warmest in the last 150 years.

Gan said the melting of glaciers, sea ice, and snowpack have significant impact because it signals the change in the water cycle and water supply of certain river basins.

While there are no glaciers in the Philippines, Gan said melting of glaciers in other parts of the world will cause sea level rise.

“For one thing, it will cause coastal erosion problems. Warmer oceans would likely cause hurricanes, typhoons and so on because oceans carry a lot of energy. There’s more energy in the oceans, more likely that you will get those extreme events that could impact Philippines in a very similar way,” he said.



A report by Climate Central indicated that several countries in the world are at risk of being submerged by 2050 due to increasing sea levels caused by climate change.

In the Philippines, major cities in Luzon, Visayas, and Mindanao could potentially be erased from the map as coastal flooding and increasing sea levels may take place in 30 years.

Based on the coastal screening tool of Climate Central, the following areas will be below the annual flood level by 2050 – Roxas City, Iloilo City, and areas of Iloilo, Antique, and Aklan.

Gan said he is not aware of the Climate Central report or the possibility that some cities, Iloilo included, would be submerged 30 years from now.

But he said sea level rises to around 3 millimeter (mm) per year “and the rate is increasing.”

“In the past, it’s just 1.8 mm year then it went on to 2.0,” he said.

By the rate it’s going, sea level rise could reach 4mm per year, partly owing to the increasing melting of ice sheets.

“It may not be completely submerged but more likely, cities will get flooding incidents like what is happening in Venice right now. These things are going to happen more often with more area flooded,” he said.

But it’s not just climate change impact. Gan said land use change would also play a vital role.

“If you will build more roads and put more concrete pavements, that will reduce the infiltration loss,” he said.

Gan said flooding is more likely to occur in concrete jungles or megacities dominated by concrete pavement.

Instead, he pushed for the use of permeable pavements.

Permeable paving is a method of paving vehicle and pedestrian pathways to enable infiltration of stormwater runoff. Permeable pavement surfaces typically include pervious concrete, porous asphalt, paving stones and interlocking pavers.

While he could not confirm the possibility of cities being submerged, he said increased flooding is always a possibility.

He pointed out, though, that there are small islands in the Pacific Ocean that are always flooded that eventually they may have to abandon or move to higher grounds.

“In the Philippines, I don’t know the terrain features but small islands, low-lying areas will have more flooding problems,” he said.

How big of a problem? “We still have to wait and see and do more studies on that,” he said.

“If the sea level increase is at 3 mm per year, in the next 50 years, you’re going to have 150mm of higher water level. So, this is not that much but it will impact low-lying areas,” he said.

The Philippines have not had much of an impact in this aspect compared to countries with snow and glaciers.



As a country, Philippines can’t do that much, Gan said.

“Simply because this will depend on major players of the world, the America, China, India, and the rest of global powers,” he said.

After all, global warming is not a local problem.

“There must be a conscious effort of those big players that can do a difference. Small players can’t do that much,” he said.

What you can small players do is to play incentive to the big players, Gan said.