The best adaptation path is to properly implement integrated planning for the Mekong Delta region.
Regarding the issue of salinity penetrating deep into the mainland in some localities, speaking with Dan Viet reporter, Mr. Nguyen Huu Thien - an independent research expert on the ecology of the Mekong Delta region said that although not severe, in the dry season of 2016 and the dry season of 2020, the Mekong River water was not too depleted, but on the branches of the Mekong River, there was still the phenomenon of salinity penetrating deep into the mainland.
Although not severe, the dry season of 2016 and the dry season of 2020 did not cause the Mekong River to run dry, but the Mekong River branches still had the phenomenon of salinity penetrating deep into the mainland. Photo: Huynh Xay
According to Mr. Thien, the above problem can be explained by two factors. One is that the tide this dry season is higher than the average of many years, the strong sea force pushes the salt water inland. The second is that the tide entering the Mekong Delta no longer has space to spread because the salt-prevention works (dykes and sluices) have been closed. The tidal water can only flow in the Mekong River's branches, cannot spread so it penetrates deep.
"From that, we can see that completely blocking saltwater intrusion in coastal areas will push the saltwater problem further inland along the main rivers," Mr. Thien commented.
Regarding subsidence in Ca Mau province, Mr. Thien said that not only this year, serious land subsidence within the freshwater areas of Ca Mau province (mostly in Tran Van Thoi district) occurred in the dry season of 2020.
The cause of this land subsidence is quite simple. Previously, these areas had two seasons: salty and fresh. During the rainy season, the water was fresh thanks to rainwater, and in the dry season, when all the rainwater evaporated, the remaining salty water from the sea came in.
After these areas were dammed to store rainwater to freshen them all year round, saltwater could no longer enter. During years of extreme El Nino drought, the amount of rainwater from the previous rainy season was exhausted at the beginning of the following dry season, causing the canals to dry up. Sometimes the bottom of the canals cracked, causing the soil to shrink and lead to subsidence.
"In places where soil is used to build roads along canals, the subsidence is even more severe, damaging the roads," Mr. Thien emphasized.
Road subsidence in Tran Van Thoi district, Ca Mau province. Photo: CM
Mr. Thien clearly stated that the subsidence phenomenon in the above-mentioned freshwater area is local subsidence, not related to the general subsidence situation of the entire Mekong Delta (caused by deep groundwater exploitation).
In order to avoid being haunted by drought and salinity every time the dry season comes, an independent expert on the ecology of the Mekong Delta region believes that the best adaptation path is to follow the integrated planning of the Mekong Delta region for the period 2021-2030, with a vision to 2050 according to Decision 287/QD-TTg issued by the Prime Minister on February 28, 2022.
According to the integrated planning, the Mekong Delta is divided into 3 regions. The freshwater core region in the upstream is the region that always has fresh water even in extreme years, so priority is given to rice, fruit trees, and freshwater aquaculture. Next is the brackish region with alternating water regimes, with fresh water in the rainy season for rice cultivation, and brackish-salt water in the dry season. For this region, it is necessary to convert the farming system to adapt to brackish-salt water in the dry season so that brackish-salt water is an opportunity and not a nightmare every dry season. As for the coastal region, which is saline all year round, it is necessary to develop a farming system that adapts to the saline regime all year round.
"If we properly implement the zoning according to the Integrated Planning of the Mekong Delta, we will not have to "struggle against salinity" every time the dry season comes, but can also take advantage of economic opportunities in salt water. Instead of continuing to entrench ourselves, "fighting" the drought and salinity with constructions in coastal areas to move the drought and salinity problem deeper inland as mentioned above and making the freshwater areas more and more fragile," Mr. Thien added.
Every 4 years there will be an extreme drought during the dry season.
According to Associate Professor Dr. Le Anh Tuan - scientific advisor of the Institute of Climate Change Research (Can Tho University), almost in a cycle from 2016, then 2020 and now 2024, every 4 years there will be a drought and saltwater intrusion higher than the average of many years. In addition to the lack of fresh water affecting agricultural production, the issue of subsidence is also of great concern.
Landslides cause damage to houses in An Minh Bac commune, U Minh Thuong district, Kien Giang province. Photo: Huynh Xay
Mr. Tuan said that in the Mekong Delta, most of the roads were built alongside the digging of canals and ditches to get soil to build up. The soil here, mechanically, must have a certain moisture content. Too much moisture will cause mushy soil, while too little moisture will cause shrinkage, leading to subsidence and landslides.
Some projects prevent saltwater intrusion, but in some extreme climates such as this year's dry season, subsidence has occurred, especially in Ca Mau. Typically, in Tran Van Thoi district, some places have subsided up to 2m. Although the locality has applied some solutions such as limiting heavy trucks from passing through roads with high risk of subsidence, even at night when there are no vehicles running, it still leads to local subsidence and landslides.
"I have been to sinking areas and found that, with projects that prevent saltwater intrusion, there is no additional freshwater supply, so the land shrinks, there is no counter-pressure, and it is easily affected and subsides. Sometimes we want to prevent saltwater intrusion and retain fresh water, but sometimes it leads to other consequences and not small damage, when the land has subsided, there is no way to raise it up. That is an uncalculated loss" - Mr. Tuan shared.
Mr. Tuan said that for many years, coastal people in the Mekong Delta have lived with drought, they will have to find solutions to reduce damage. Many people have invested in salinity meters themselves, then announced it to each other in the community. In freshwater areas, without needing forecasts from authorities, they have forecasted and prepared to respond, such as planting rice earlier to avoid drought and salinity. Although the government's direction is to plant rice before the end of December 2023, many areas have already planted rice in mid-November 2023.
People also know how to change production, instead of growing two rice crops, people rotate rice - shrimp to adapt. People also know how to store water in their conditions, the image of water tanks is always there, so it reduces a lot of pressure on domestic water supply.
However, due to the increasingly complex developments of drought and salinity intrusion, it is necessary to strengthen forecasting and early warning, and inform the people. At the same time, there must be solutions to create new livelihoods for the people, at which point drought and salinity can be considered not to be a serious problem.
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