Awareness on previous and current hydrological condition in Mekong river basin due to climate change  

Climate Change phenomenon is difficult to predict when temperature slowly increases which has an impact on ecosystem in all region. Especially in terms of hydrological aspect, climate change leads to the highly frequent and severe drought and flood, resulting in significant impacts on socio-economy status of nations worldwide including Mekong riparian countries. Based on meteorology data, in Lower Mekong river basin especially the north and middle part of Lao PDR, the amount of rainfall during dry season in 2019 from October 2018  to April 2019 is less than the amount of rainfall from the previous year which accounts for only 60 percent for the same period. 

To deal with such situation, many nations have utilized a number of technology and measures for flood and drought mitigation and management. The most popular one is the construction of reservoir for irrigation purpose. This will help to store water from wet season and supply water during dry season. The function of this type reservoir is similar to hydropower dam which is not only for energy generation, but also for flood and drought mitigation.

The explicit benefit from such infrastructure can be demonstrated that during 6 months of the end of year 2019, despite a shortage of rainfall in Mekong river region especially the north and middle part of Laos, water level along Mekong mainstream remains in the normal condition. This is because of the flow contribution from dam reservoirs. This statement can be verified by monitoring data along Mekong mainstream in Lao PDR in dry season period in 2019 at Vientiane, Pakson, Thakek, Savannakhet and Pakse stations. It is emphasized that water level condition is normal in which water level is above the long-term average value in dry season from 1962-2009. Similarly, in relation to monitoring data at Chiang Saen station, flow rate from upstream part in Dry season of year 2019 is still in the normal condition. In addition, water level is also higher than long-term average value from 1962-2009. 

The release of water from upper Mekong river basin is the outcome of the cooperation among nations in Lancang-Mekong region. Last November 2019, Minister of Natural Resources and Environment reported to Vientiane time about the cooperation on water resources that “As the upstream nations of Lancang-Mekong river basin, China has responsibility to share data to downstream nations and is always ready to conduct emergency response. In 2016, riparian nations faced the severe drought for 1 in 100 annual reoccurrence intervals. To mitigate such drought issue, China also release emergency supplement water in efficiency manner which has been praised by the government of lower Mekong countries including Lao PDR and international organizations. This shows the spirit of cooperation from 6 countries who rely on and support each other as one family, contributing to great status of cooperation on  water resources among  6 cooperation countries". 

Regarding the report between Ministry of water resources and Mekong river commission secretariat on joint monitoring on emergency water supplementary from china, It demonstrates that "China conducted emergency water supplementary from March to May 2016 by releasing water from Lancang river to Mekong river which is higher than normal natural flow at same period accounting for 1000 meter per second, resulting in the increase of water level along Mekong Mainstream".

Apart from that, statistical analysis from previous year also demonstrates that the amount of rainfall in 2019 in river sub basin is less than the amount occurred from previous year. For instance, 6 month beginning of year 2019, the amount of rainfall at Nam Ou river basin decreases down 41% compared to the value at the same period in year 2019 and decrease downs to 29% at July to September 2019. For Nam Ngum  river basin, this phenomenon affects directly to this basin because of  less amount of rainfall and low frequency of rainfall event. This is demonstrated by monitored rainfall at Pakkagoung station which has only 1086.6 mm in year 2019. When compared with the amount in year 2014 (1937.5 mm), 2015 (2101.8 mm), 2016 (1564.6 mm), 2017 (1376 mm) and 2018 (1652.4 mm) respectively, the amount of rainfall decreases significantly 566.1 mm average approximately. In addition, such rainfall shortage leads to low inflow to Nam Ngum dam 1 in year 2019 which decreases 30 %. Even though the shortage of inflow, water in dry season at downstream is still sufficient because of mobilization of water resources from 5 reservoir in Nam Ngum river basin which the main tributary of Mekong river basin through the optimal reservoir operation. Therefore, water can be allocated efficiently under drought condition.

In line with that, Ministry of Natural Resources and Environment also support the drought mitigation through the close cooperation with key line agencies for reservoir operation especially water storage and release from reservoir, river monitoring, drought forecast in order to disseminate information to stakeholders for drought response planning and also to contribute to drought management in Mekong river basin.   

In addition to existing mitigation and management measures, it is also recommended to conduct a feasibility study and construct the reservoir in suitable area in each district and province. Furthermore, it is also required proper strategy and action plan for water operation and irrigation system in each reservoir located in river basin systematicalway, mainly hydropower dam reservoir by considering the involvement of key line agencies and local authority.

It is also required the enhancement of the cooperation with nations in subregion, region and international level including under the existing cooperation framework such as Sustainable Mekong Agreement Cooperation  1995, Lancang-Mekong Cooperation,  Greater Mekong Subregion by considering flood and drought as a continuous new normal which has direct impacts on livelihood and wellbeing as well as the national socio-economic development to deal with in the right and prompt manner to ensure the green growth and sustainable development of the nation.