In the past, seldom was there any report of water supply dams drying up. That is because these dams and the water treatment plants they served were designed for a 1 in 30-year drought severity. Statistically speaking, water supply shortage will not occur more than once in thirty years.

Nowadays we often hear of water levels of our dams falling to near critical levels during the dry season once every other year although we are not experiencing a drought severity of 1-in-30 year. Invariably the authorities blame the lack of rain in the catchment areas.

The lack of rain during the dry months with water levels falling and the recharge of the dams until they are full during the annual raining season have been factored in when consultants designed the dams.

Then why is it that we are now so very often threatened with water shortage? Is it because climatic conditions have changed drastically or is it because there has undue disturbance of the catchment areas or something else like bad operational management.

In the Klang Valley there have been two clear examples of overdrawing from the dams. One is the Sungai Langat Dam, designed for a safe yield of 382 million liters per day (mld) but the treatment plant it serves has been producing 463 mld. This 21% overdraw is causing the drastic drop in water level in the dam.

The other example is the Klang Gates Dam, which was designed to supply solely the Bukit Nanas treatment plant with 168 mld of raw water since 1957. But during the 1998 water crisis, a treatment plant was built in Wangsa Maju drawing 45 mld of water from the same dam. Overdrawing in this case is why the dam is drying up fast.

The drying up of the Sungai Terip Dam in the Seremban District where water rationing has been imposed is yet another such example of bad operational management.

Instead of simply blaming the weather, the authorities should carry out a comprehensive review of the safe yields of dams and ensure that we do not overdraw water from these dams beyond the revised safe yields. Otherwise we will be perennially in trouble!

Note:

An edited version of the above was published in The Star on 25/08/05.