Absence of seasonal flooding washes away Mekong Delta livelihood

For several years, the annual flooding that has nourished the delta for centuries has been late, deficient or absent, and experts have blamed it on climate change and the construction of a series of upstream dams.

Early this month, Thang, 48, and his wife, Khen, residents of Hong Ngu District in Dong Thap Province, took their boat and went to collect their catch from fixed-net fishing in a waterway near their home.

"I've put 50 sets and am getting 30 kilos of fish per day on an average, which is just half of what I used to get," Thang said.

"Most of this waterway is rainwater and water discharged from fish ponds in the area. There's not much floodwater," he said, adding that with water staying low, there was not much fish to catch.

Khen shows the fish caught in her husband's net in Dong Thap Province, November 2021. Photo by VnExpress/Ngoc Tai

The couple said this year, the seasonal flooding did not happen until September, and the water has already receded since early November, shortening their fishing season to just a month instead of up to around three months in the old days.

Unlike the floods that cause huge damages, the annual flooding in the Mekong Delta has been a boon for the region, delivering great benefits for residents and the regional economy, especially the Plain of Reeds, a wetland straddling Long An and Dong Thap provinces.

People in the delta, which is on the downstream reaches of the Mekong River, have for generations depended on the floodwaters to inundate their fields before sowing seeds directly.

Previously, the flooding would start late July or early August and remain until November or even later, blessing the region with extraordinary fertility as they deposit silt from upstream areas.

The floodwater, especially overland water, provided migration routes and breeding sites for many species of fish, distributed sediment that retained nutrients for agriculture, recharged groundwater aquifers, and prevented salt intrusion, not to mention washing away all the chemical residues left from previous crops.

When the annual flooding does not happen or happens late, cropping and fishing activities are disrupted.

Thang and Khen have been earning a living from fishing for 20 years. They said that in the past they and other fishermen did not have to go anywhere far from their neighborhood in Thuong Thoi Thien Commune to look for fish, and there was plenty to catch.

The river was such an abundant source of fish that they could easily engage in sustainable fishing, only catching full grown fish and letting others go.

But things have changed drastically over the years. For at least four years now, they've had to travel far to look for fish and collect all the fish in their nets, not letting any go.

Ho Van So, another Dong Thap native, is not a fisherman, but relies on local waterways for his livelihood.

He makes money by catching moina, a crustacean species that are normally used to feed fingerlings, and selling them to fish farmers. The annual flooding season is also peak moina season.

So tries to make the best of flooding season even now. He spends several hours each day in the water, catching as many moina as he can.

Ho Van So catches moina in Dong Thap Province, November 2021. Photo by VnExpress/Ngoc Tai

Around 2km from where So catches moina, some people build small mounds along the waterway, placing some food to lure eels and catch them.

The work requires certain expertise and patience because "eels would never come to such mounds if there was the slightest movement," said Pham Van Duong, an eel catcher.

When the wet season is gone, people like Duong, Son, Thang and Khen switch to other seasonal jobs, but the annual flooding and its natural benefits has been their peak earning season for long.

Today, they are aware that sooner or later, they will have to find other ways to make a living.

Khuong Le Binh, director of the Dong Thap hydro-meteorological station, said apart from the low flooding levels, the volume of rainfall this rainy season has been 13 percent lower than the average of previous years. The southern region of Vietnam, including the Mekong Delta, has only two seasons: the dry and the rainy season, the latter normally lasting from late April to November, including the flooding season.

Binh said that this year, the flood level in Dong Thap was 0.1-0.2 meters lower than last year and 0.4-1.3 meters lower than in previous years.

Nguyen Huu Thien, an expert on Mekong Delta ecology, said the upstream hydropower dams were holding back a significant volume of water, causing low levels of flooding in downstream areas.

He also noted a drop in the amount of rainfall in southern Vietnam this rainy season.

"In the near future, authorities should come up with solutions to help locals adapt to the absence of seasonal flooding and switch to other livelihoods."

During the last dry season, saline levels of up to six grams per liter were found in some areas. Salinity of one to four grams was found 50 kilometers (31 miles) upstream on average, and up to 130 kilometers, in all tributaries of the Mekong. Salinity above one gram is considered unpalatable and levels of above two unsafe for most crops.

The provinces of Ben Tre, Tien Giang, Long An, Kien Giang, Ca Mau and Soc Trang had to declare a state of emergency after drought and saltwater damaged around 43,000 hectares (166 acres) of rice fields and 80,000 families suffered acute water shortage.