From the Khmer Times, February 15th 2021
The Mekong River Commission (MRC) on Friday raised the alarm about declining river water levels causing a negative impact on river transport, fish migration, agriculture irrigation and river weed collection.
It said the considerable drop since the beginning of the year is due to lower rainfall, flow changes upstream, hydropower operations in the Mekong tributaries and outflow restrictions from Jinghong Dam in China.
The analysis released by MRC states that in Cambodia, the river water levels at Kampong Cham and Neak Loeung on the Mekong, at Phnom Penh on the Bassac and at Prek Kdam on the Tonle Sap have been declining steadily and have remained lower than their long-term averages since early November. It shows that since January, an average daily drop of 0.2 metres has been observed.
It also recorded that water levels along the Mekong in Stung Treng and Kratie provinces fluctuated between -0.02 metres and 0.05 metres. However, the levels remain higher than the long-term average.
Winai Wangpimool, director of the MRC Secretariat’s Technical Support Division, said that it is are calling on China and the Lower Mekong countries to share their water release plans to help the Lower Mekong countries manage risks more effectively.
In August last year, the MRC recorded a low flow of water in the Tonle Sap Lake due to extremely dry conditions, with reverse flows at their lowest on record since 1997.
The report pointed out that the low flow of water could have severe impacts including loss of fisheries and irrigation in Cambodia. A reduction in fish catch is predicted, threatening food security for the most vulnerable communities in the region.
The Tonle Sap Lake is the largest and most productive inland lake in Southeast Asia. It is considered one of the world’s biodiversity hotspots and the Mekong’s main fish factory.
Fishermen living in core areas of the Tonle Sap Biosphere Reserve in Kampong Thom province have reported to Unesco that fishing yields have been declining over the last three years due to low water levels in the wet season, forest fires in the dry season and climate change during a survey conducted last month.
“There have been sudden rises and falls in water levels immediately downstream of Jinghong (China) and further down to Vientiane (Laos), which has been challenging for authorities and communities to prepare for and respond to possible impacts,” Wangpimool added.
Meanwhile, the Mekong in Thailand’s north-eastern province Nakhon Phanom has recently begun to acquire an aquamarine colour or blue-green water phenomenon due to the low flow of water. The fine sediments normally found in the fast-flowing and deeper water that give the river its brownish appearance are no longer present, creating clearer water conditions.
“When sunlight hits the river, the clearer water absorbs what are known as “long-wavelength colours” at the red end of the light spectrum, which gives the river its blue-green hue. The clearer water allows microscopic plants or algae to grow on the sand and bedrock river bottom turning the margins of the river green. Algae are normally flushed away by the river current, but due to the low water levels it has accumulated in certain sections of the river,” the analysis from MRC explains.
So Nam, MRC Secretariat’s chief environment management officer, said that this is exactly the same situation which happened in late 2019.
“Today’s blue-green water phenomenon is likely to spread to other stretches of the Mekong where low flows are experienced,” he said, adding that this will in turn affect the productivity of aquatic biodiversity, reducing fish catches and threatening the livelihoods of local communities with less food available for aquatic insects, invertebrates and small fish.
Nam also said that the Mekong’s blue-green appearance may persist until flows increase with the onset of the next flood season, which usually begins in late May and normal conditions may be restored if large volumes of water are released from storage reservoirs in the Upper Mekong (Lancang) dams and tributary dams, which would mobilise sediments and return the Mekong to its typically brown appearance.