Lack of supply in a number of places. This phenomenon is caused by the uneven rainfall between areas as well as within an area in the country. The distribution of rainfall is uneven from season to season and from year to year. As a result of this unevenness of rainfall distribution, the surface water flow, especially in rivers, differs in quantity and speed.
In developing areas where a large supply of water is required, the surface water during times of drought is insufficient to meet the demand for water. During monsoon seasons, however, the water supply exceeds the demand while the existing rivers have a problem accommodating the total surface water. This results in flooding.
Another obvious phenomenon which threatens our country’s water resources is the decrease in quality of river water. The water of a river is unpolluted at the beginning. However, as it flows through populated areas, the quality deteriorates. The deterioration of water quality occurs in tandem with increasing development of the area.
Flood control and prevention functions fall under the Department of Irrigation and Drainage, Ministry of Natural Resources and Environment, Malaysia. The department plans and implements throughout the country flood mitigation projects such as flood control dams, detention storages, river improvements, diversion channels and drainage pumps. The projects are funded by Federal Government of Malaysia. The operation and maintenance are normally carried out by respective state governments.