FRESHWATER resources are under global stress for a variety of reasons. A spiralling population demands more water for crops, dairy and energy. Therefore, rivers are being fettered with storage and diversion structures. Endless thirst upstream deprives deltaic ecosystems of vital environmental flows. As rivers dry up, their deltas are suffocating. In one study, scientists examined 33 river deltas worldwide and concluded that 24 were experiencing environmental degradation. Some of these deltas bear a striking resemblance to the plight of the Indus delta.
The Yangtze river is the longest in Asia and the third-longest in the world. The basin provides about half of all the fish and two-thirds of the rice consumed in China. The river is dotted with thousands of storage sites, constructed since the 1950s. The Three Gorges Dam, the world’s biggest hydropower project, inundated 13 large cities, 140 towns and 326 villages, displacing over a million people. Massive upstream diversion has played havoc with its delta. Due to the lack of environmental flows, undiluted flows from industries and agricultural farms have increased pollution to perilous levels. The area’s wildlife is under severe stress, and its dolphins have vanished.
The Mekong is the longest river in Southeast Asia and the 12th longest in the world. The Mekong river runs through China, Myanmar, Laos, Thailand, Cambodia, and Vietnam. Only two decades ago, the Mekong carried some 143 million tonnes of sediment to its delta every year. China has built a cascade of hydroelectric dams on its tributaries and 11 dams on the main river since 1995. Laos, one of the riparian countries, has also constructed the Xayaburi and Don Sahong dams. These dams now trap much of the river’s sediment.
The Mekong River Commission has revealed that in 2020, only about a third of its silt reached the Vietnamese floodplains. The commission estimated that the quantum would reduce to less than five million tonnes annually by 2040. Its mangrove ecosystem has been rapidly degraded.
Deltaic ecosystems are being pushed towards extinction.
In 1973, the total area of mangrove forests in the delta was 185,800 hectares (around 460,000 acres), declining to 102,160 hectares (around 252,442 acres) in 2020. The delta contributes significantly to Vietnam’s economy. It constitutes 12 per cent of the country’s territory and provides 54pc of rice, 60pc of fruit and 70pc of seafood. As of 2022, the delta accounted for 70pc of Vietnam’s aquaculture.
The World Wide Fund for Nature has warned that the Mekong delta is shrinking and sinking. The WWF has also noted that seawater intrusion is intensifying due to riverbed erosion; salt intrusion has been observed up to 130 kilometres inland. Reduced sediment flows were identified as a key driver of coastal erosion at 400 locations. Lower riparian countries complain that China does not share sediment flow data with them.
The Nile delta is another pertinent case. Some 7,000km long, the Nile is the longest river in the world. Traversing through 11 African countries — Burundi, DRC, Egypt, Eritrea, Ethiopia, Kenya, Rwanda, South Sudan, Sudan, Tanzania, and Uganda — the river meets the Mediterranean Sea north of Cairo. The Nile delta is regarded as the cradle of Egyptian civilisation and as one of the oldest cultivated areas on earth. Most of Egypt’s agricultural activity is concentrated in the delta region — the fisheries in the region account for 12.5pc of Egypt’s total fish production. The rise in sea level, declined sediment flow due to dams, and coastal erosion pose a serious threat to the delta’s ecology. Soil salinisation and a loss of agricultural land are endangering the food security of millions of Egyptians.
Mediterranean levels are increasing by 3.2 millimetres annually, devouring 35-75 metres of the coastline every year. Since the 1960s, the Aswan Dam has trapped the Nile’s silt, preventing it from reaching the delta and allowing the sea to encroach upon fertile land. By the 2020s, this had turned 15pc of the most fertile farmland into wasteland. The rapid rise of the urban population is diverting more water for industrial and agricultural expansion. A satellite data analysis has revealed a 2.26pc decline in the agricultural land area between 1990 and 2023. Satellite imagery also confirms the recession of the shoreline by about 840m during the same period. The situation is likely to be further exacerbated by the construction of the Grand Ethiopian Renaissance Dam, Africa’s largest dam.
Never-ending human greed for food and energy is pushing pristine deltaic ecosystems towards extinction.
The writer is a senior adviser on water governance at the Sustainable Development Policy Institute.
Published in Dawn, August 17th, 2026
