The current water level on the mainstream of the Mekong River is significantly below average in northern Laos and Thailand, according to the Mekong River Commission (MRC).
The MRC said levels at the mainstream measuring stations at Chiang Saen, Chiang Khan, Luang Prabang, Vientiane and Nong Khai are below those that occurred in the low flow season of 1993, which followed the most extreme regional drought on record in 1992.
"All mainstream water levels measured north of Strung Treng are significantly below the average for this time of year and are expected to decrease further for another month," says the MRC.
"Similarly, the river levels in Southwestern China have been at their lowest in 50 years, with water flowing at only half the level that would be considered normal for February."
Such low water levels on the mainstream Mekong are the result of drought conditions in northern Thailand and Laos, and are part of a wider regional drought being experienced upstream in Yunnan Province in China.
The 2009 flood season was drier than normal with wet-season river levels in Vientiane, for example, being among the fifth lowest levels on record in the last 98 years.
Starting from that low base, analysis of the rainfall at selected hydrological stations in Yunnan, Chiang Saen and Luang Prabang has shown a consistent pattern of monthly precipitation significantly below average amounts since last September.
For example, the rainfall recorded at Chiang Saen, Thailand in November and December was only 20mm compared to the long term average of 52mm for the same period, contributing to the low river flow.
The very low water levels recorded at monitoring stations in the mainstream between Chiang Saen and Nong Khai show that tributaries in Laos and Thailand are not feeding as much water into the mainstream as would be expected.
For instance, this can be seen with the Nam Khan River that flows into the Mekong at Luang Prabang. Water levels in the Nam Khan are the lowest for 50 years.
The implications of these low water levels are serious for the people of northern Laos and Thailand.
Severe drought will have an impact on agriculture, food security, access to clean water and river transport and will affect the economic development of people already facing serious poverty. The northern provinces are among the poorest areas for both Laos and Thailand.
The MRC said River tour operators have stopped offering services on the stretch of river between Houiesay and Luang Prabang in Laos.
It has been reported that Yunnan provincial authorities have halted the operation of Chinese cargo boats which will affect regional trade.
The National Centre for Environmental Health and Water Supply in Laos has started advising people to counter the effects of drought by reducing water consumption.
The MRC is undertaking more detailed assessments of the low flow conditions and is working with its member countries to closely monitor the drought situation as well as integrating drought management considerations into its climate change adaptation initiative.