Classic case of robbing Peter to pay Paul


The original title of this article is:  Overdrawn Langat Dam causing shortage

Familiar alarm bells are ringing once again when Perbadanran Urus Air Selangor Bhd (PUAS) warned that Kajang and nearby areas would face water cuts soon as water production in Sungai Langat treatment plant dropped by 20% from its normal production of 470 million liters per day (mld) due to falling water level in Sungai Langat Dam (The Star, 11 Sept, 04).

In recent years, and in increasing frequency, water supply in the Klang Valley especially served by dams seems to be the most problematic. The first such problem was during the 1998 water crisis when El Nino effect was generally accepted as the main cause for water shortages through out the Klang Valley.

Then in early 2002, certain areas in the Klang Valley were subject to low water pressures and intermittent supplies. The water levels in the three major water supply dams were shown to have fallen to dangerous levels due to little or no rain falling in their catchment areas.

The current scenario is very much a reminiscence of the 2002 water shortage except that this time only the Sungai Langat Dam is facing the problem. Hopefully other dams will not suffer a similar fate.

Malaysian water supplies, with or without dams, were designed for a 1 in 30-year drought (now 1 in 50). This is to ensure that water shortage would not occur more than once in thirty years, statistically speaking.

How is it then that we are having such frequent water shortages from Sungai Langat Dam? Has the weather pattern affecting the Langat Dam changed due to man-made changes to the environment?

From published data, its safe yield, based on a 1 in 30-year drought, is only 386 mld. However, its “normal water production” is reported to have been 470 mld for quite some time. This works out to an overdraw of over 20%, which in turn translates to a drought of once in less than 5 years!

It was reported that PUAS, in its attempt to overcome the water shortage, is pumping raw water from Sungai Semenyih Dam to Sungai Langat Dam at the rate of 10 to 15 million gallons per day (Star Metro, 13 Sept. 04).

But Sungai Semenyih Dam is also being overdrawn and is vulnerable to water shortage. Isn’t it a classic case of robbing Peter to pay Paul?

The need to overdraw from dams is simply that the authorities have not been able to develop new sources fast enough to keep pace with the rise in demand. Therefore it is difficult to fathom why there is such complacency on the part of the authorities in dragging their feet in the implementation of Selangor/Pahang interstate water transfer project. 2007