Despite the successes, the GMS has limitations causing obstacles to the long-term development. This region is rich in potential, but GMS is still underdeveloped area; there are significant disparities in the level and resources among countries and localities. Particularly, the general and specific benefits between countries as well as external partners have many differences in solving many problems in terms of water resources, environment and geographical territory. Overarching problem is lack of strong mechanisms to enforce the commitments, agreements and international conventions.
The World Wild Fund for Nature (WWF) noted the water level of the Mekong River was down to alarming level; the New Scientistevaluated: “China drains life from Mekong river”. A series of mass media such as Reuters AlertNet, The Guardian, and Bangkok Post warned Mekong river shallows because of dams; dams are built and river gradually dies or shallows due to the dams. Most is blamed for the construction of large dams on upstream in China.
China has massively exploited the Mekong River, continuously built the giant hydroelectric dams, and cleared the river sections causing serious impact to water resources, fisheries, sediment and especially pollution to the downstream. In the dry season, the downstream water level never downs to a record level as the Yunnan dams put into operation.
Along with flow exhaustion, global rising temperature has adverse effects to the rain regime, increase in the number and extent of the extremes of weather; changes the mainstream and sub-streams, strongly impacts on the migration of fish species, total flow discharge and sedimentation. Observation data in recent years show that, the rainfall of the basin heavily decreased in the dry season and increased in the rainy season. Increase in risk of floods and droughts has adversely affected agricultural production and residents’ life; especially the poor is vulnerable. In the current trend, MRC forecasts the next 20 years, along with rising temperature, precipitation will increase 200mm in the basin, total flow discharge will increase from 512 billion m3 to 619 billion m3 (increase in 20%). With increase in discharge of 22 % (from 13.600m3/s to 16 592 m3/s) in Kratie – Pnonpenh (about 3.600km2), frequency of flooding will increase from 5% to 76% and time of flooding will increase over 12%.
The water transfer projects from China to Thailand can reduce the discharge supplied to the Mekong downstream and Mekong Delta will be subject to interference effects between the upstream river and the downstream sea. When the river weakened, seawater will encroach inland, causing deeper salt intrusion. On the other hand, deforestation of the basin upstream in the dam chain beyond calculation can cause greater risks in size and degree of influence. Double impact of climate change with rising sea levels caused many lands to be subject to saltwater intrusion, high water in flood season, and low water in dry season. This adverse affect and the impact of hydroelectric dams can drastically reduce the amount of silt, change the flow, affect the aquatic resources and lose the people’s livelihoods. According to observation data from 1993 to 2003, the silt rotation process to the downstream at Chiang Sach (Thailand) has dropped 56%.