State of water environmental issues
2.1.3. Detailed survey of rainfall and surface water in the Mekong catchment
Surveys on existing water resources and related factors for both surface and ground waters at specific target areas were conducted by the Ministry of Water Resources and Meteorology in collaboration with concerned ministries, with the technical cooperation and support of the Mekong River Commission, international organisations and donor countries.
Cambodia has access to substantial surface water resources. On average, the annual inflow from upstream countries is estimated at 410 km³ and internally generated flows of 90 km³ per year (Ministry of Water Resources and Meteorology, 2003). In Cambodia, the Mekong River flows from north to south, over a distance of about 480 km. The river’s drainage basin covers about 86 percent of the land area of the country. The Mekong River brings yearly floods of about 475 km³, and before flowing downstream, inundates the lowlands, where the floodwaters partially enter the Tonle Sap Lake and eventually flow down the Mekong and Bassac rivers.
The rainy season occurs from May to October, which is the monsoon season. The annual mean rainfall ranges from 1,280 mm/year to 1,520 mm/year. Figures have shown that there are two peak mean rainfalls: one takes place in October, which is near the end of the rainy season; and the other generally occurs in May. The driest month is February.
The average rainfall in the eastern part of the sub-area delta is high compared with other locations, ranging from 1,173.4 to 1,866.6 mm/year. The southwest zone of the area generally has the smallest annual rainfall, ranging from 936.8 to 1,816.5 mm/year.
2.1.3.1. Data of river discharge in study areas
The discharge during the dry season (April to May) in 2003 is shown in the table below. A study by JICA has indicated that the dry season flows in the Cambodian floodplains are strongly affected by tidal fluctuations.
Table 4: Effects of tidal fluctuations to the dry season flow
| Station |
Average Flow
(m³/sec) |
Range of Fluctuation
(m³/sec) |
Fluctuation Rate
(percent) |
| Kampong Cham |
1,600 |
100 |
6 |
| Chrui Changvar |
2,000 |
1,500 |
75 |
| Neak Luong |
3,000 |
3,000 |
100 |
| Monivong Bridge |
100 |
150 |
150 |
|
Source: WUP-JICA, 2004
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- Table of contents > 2. River Basins > 2.1. The Mekong River System (Basin)
- 2.1.1. Introduction
- 2.1.2. Mekong River tributaries and Rainfall
- 2.1.3. Detailed survey of rainfall and surface water in the Mekong catchment
- 2.1.3.1. Data of river discharge in study areas
- 2.1.3.2. Data on water demands in study areas
- 2.1.4. Water environment in the Mekong River systems
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