Oct 23
DAM IF YOU DO, DAM IF YOU DON’T by Vincent M. Ragay  |  Posted in Articles  |  on Fri, Oct 23, 2009

Even in the aftermath of Ondoy and Pepeng, our country continues to reel and roll like an empty steel barrel careening on a rampaging river fed by a monstrous tropical cyclone. Also, it seems those two killer visitors brought out the many hidden cracks in the already weakened foundations of our society.

In an effort to find out what happened, many voices – official and unofficial, wise and otherwise – have expressed exasperation, anger and hopelessness over the government’s neglect, mismanagement and unpreparedness in the face of disasters. One major target of public indignation was the NAPOCOR engineers’ supposedly untimely release of waters from San Roque Dam. That is, the flooding in Central Luzon was caused by delayed release of water. Lawmakers and critics were quick to release their own putrid floodwaters upon those beleaguered engineers during a Senate hearing.

Flood us and we will flood you!

But the engineers did exactly what they were supposed to do, for several simple reasons:

1. A dam’s purpose is to, well, dam water in order to store as much water as possible for future use. As the rains fall, dams are filled up to their optimum carrying capacity.

2. When there is more rainfall than needed to fill up the reservoir, water is allowed to spill over to protect the structural integrity of dams.

3. The timing (when) and the rate of release (how much per minute) of water from a dam is left for engineers to determine. Obviously, on the side of certainty, engineers would have to assume that a typhoon’s rainfall is the last chance it has to impound enough water to capacity level. Hence, the time of release would be that moment just before or, possibly, when capacity has been reached. Again, that would be a decision based on the rate the dam is filling up. So, whether we have a fast-filling or a slow-filling rainfall, the amount of water to be released will be computed based on when the rains (assuming it does not cease) will fill up the dam.

To make it simpler, when taking a bath using a pail and a tub, you take out as much water from the pail at about the same rate the pail is filling up. This is to prevent the pail from overflowing. One may get water as fast as possible to keep the water low. But in the dam’s case, the rain may not stop and the release of more water becomes inevitable. It fills up and water has to be released. Hence, the rate is both determined by the rate of the rainfall and how much water has been stored.

4. Furthermore, the rate of rainfall – hence, the corresponding rate of release — is complicated by the added effect of water runoff within a dam’s watershed (the enclosed area that captures the rain and collects all that water behind the dam). The less forest cover there is, the greater the rate a dam fills up.

In brief, we see that dam operators base their decisions on their objectives of storing water, of releasing water to feed irrigation canals as needed, of generating power and of alleviating (not preventing) flooding during the rainy season. The tricky nature of the fourth role puts the operators between nature’s unpredictable ways and people’s unsavory opinions.

Flooding, when there is more rain than the land can absorb or handle, is inevitable and is further aggravated by the denudation of forest covers in the dam’s surrounding watershed and the failure of waterways to drain waters readily to the sea. To blame dam engineers for flooding is too much to ask for these people who must work only within the reasonable parameters that nature will allow. If they must be blamed, blame also the other engineers who fail to dredge creeks and rivers, the politicians who allow people to build houses along water channels and the illegal loggers who destroy forests.

Maybe we can blame nature for its unpredictable ways. But why blame anyone or anything at all? Are engineers such clueless and heartless creatures that they should take all the blame?

There is a simpler way to look at this issue graphically and more clearly. Look at it this way: If there was no dam, would there have been flooding? Of course! In 1972 when Central Luzon was flooded, there were still no San Roque or Pantabangan Dams. Who did we blame way back then in the absence of dam engineers? They built the dams, precisely, to alleviate flooding. The fact that the dams are there should be reason for us to be thankful that the flooding did not reach Noah-ic magnitudes!

There is a corollary illustration which will finally bring home the point and help ordinary readers to put the blame where it should put or, if not, thrown where it should be discarded entirely. This was brought to my mind while I traversed the Candaba Viaduct along NLEX. Cruising in a bus above the glistening floodwaters that covered the Candaba Swamp, one can appreciate the unchallenged prominence of Mt. Arayat over the Pampanga rice fields. I almost felt like Noah seeing Mt. Ararat itself rising above the receding Great Flood. What is this anomalous mount doing in the vast expanse of Central Plains of Luzon? It looks out of place. It should not be there at all!

During Ondoy’s visit, Arayat town in Pampanga was flooded and remains so at the present. But what if Mt. Arayat had not been there at all? Would there have been a flood? Of course! The mountain – like a dam – absorbs or stores as much rainfall as it can through its soil, its underground aquifers, its trees, its animals and its vegetation. Beyond that, the rivers carry the excess water to the lowlands. Anything not stored on the mountain and carried away by the river to the sea, will remain as floodwaters. If Mt. Arayat had not been there, imagine how much worse the flooding would have been in Arayat and its neighboring towns?

A dam then is a veritable mountain that stores water. It holds visible water while a mountain hides it. Humans built the first; God provided the second. Let us be thankful we have dams and we have forested mountains like Mt. Arayat that can still absorb enough water. Maybe, just maybe, we could blame sin for the flooding that occurred. It has happened once or twice before. But that might not be something an engineer should say. Yet, as one, I would gladly take the blame for I, too, am a sinner.

We have some of the most diligent and intelligent engineers in the world. Many of them work in the best companies in Asia, in the Middle East and in the major industrial countries. To make them culpable for a disaster that they did not cause is an injustice. To accuse them of wrongdoing in spite of their having done their work well is pitifully foolish.

If there were no politicians or journalists who spoke as if they already knew the conclusions before the technical people were able to explain fully and clearly how civil works functioned, or, who listened and failed to understand as they should have, we would still have a society that would operate. Perhaps, it will function even much better.


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