A nearly dead delta

Pakistan's vital Indus River Delta, a historically fertile and ecologically rich region, is disappearing at an alarming rate, facing a catastrophic crisis driven by drastically reduced river flows, land erosion, and relentless sea intrusion, exacerbated by climate change. Environmental data reveals a stark reality: the delta has shrunk by a staggering 92 per cent since 1883.

Once a sprawling lifeblood covering approximately 12,900 square kilometres, the delta’s active area had dwindled to nearly 1,000 square kilometres by 2018. This dramatic decline signals a profound environmental catastrophe unfolding along Pakistan's coast, with consequences reaching far beyond the immediate delta region.

The dramatic reduction in freshwater and sediment reaching the delta from the Indus River, primarily due to interventions upstream, is essentially the basic issue at hand. One of the predominant sources of this degradation is the severely curtailed water discharge downstream of the Kotri Barrage.

Historically, before major dam and barrage construction began in earnest around 1930, the annual flow reaching the delta (downstream Kotri) was estimated at a massive 150 million acre feet (maf). This flow carried over 400 million tons of vital silt annually, the building blocks of the delta itself.

However, the construction of extensive upstream dams, barrages and large-scale irrigation networks, while serving agricultural and power needs elsewhere, choked the river's final reach. By the 1950s, downstream flow had plummeted to around 80 maf. The situation worsened dramatically over subsequent decades, reaching a record low of just 1.5 maf in the drought years of 2001-2002.

While a consensus now suggests a minimum environmental flow of 10 maf is needed downstream of Kotri to sustain the delta's basic functions, officials concede this target is often not met. This chronic, century-long reduction in flow has slashed the crucial sediment supply to a mere 26-30 million tons per year.

The result is a delta effectively starved of the materials needed to maintain itself against the sea. The once-extensive mudflats are decaying, and the vast silt-deposit deficit accumulated over nearly a century is considered almost irreparable. The fundamental ecology of the delta has been irrevocably altered.

The consequences of this diminished freshwater outflow are starkly visible along the Sindh coast. Without the river's pushback and sediment replenishment, the powerful Arabian Sea advances relentlessly inland – a phenomenon known as sea intrusion. Since 1956, an estimated 3.5 million acres of land, much of it previously fertile agricultural area, have been swallowed by the sea.

This humanmade crisis is being amplified by global climate change. The Himalayan glaciers, the source feeding the Indus River, are melting at unprecedented rates – average retreats approach 15 meters per year in some areas. While initially increasing meltwater, the long-term depletion of these ‘water towers’ poses a grave risk to the river system's stability.

Simultaneously, global sea levels are rising, with the South Asian region experiencing an average increase of 3.7 millimetres per year – a rate reportedly doubling over the last two decades. Projections suggest a potential rise of up to one meter by 2100 under high-emissions scenarios. This rise directly exacerbates coastal erosion and sea intrusion, pushing saltwater further into the weakened delta.

The loss of the Indus Delta is a tragedy extending far beyond the landmass. River deltas are ecological and economic powerhouses. They offer exceptionally fertile land, support vast fisheries through their nurseries in wetlands and mangroves, act as natural buffers against storm surges, and host unique biodiversity.

The Indus Delta, characterised by its mix of riverine and tidal influences (though increasingly dominated by the latter due to low river flows), boasts one of the world's largest arid mangrove ecosystems (a Ramsar Site). This habitat is critical for countless species. Its degradation means losing these invaluable services, impacting food security, coastal safety, and natural heritage.

The catastrophic shrinkage of the Indus Delta is an environmental emergency demanding immediate, strategic action. However, addressing the core issue – ensuring adequate freshwater and sediment flow downstream Kotri – is entangled in complex water rights disputes.

Experts warn that without tackling this fundamental water management issue head-on, proposed solutions like coastal defences or mangrove replanting, while potentially helpful, may only be cosmetic.

A comprehensive, politically challenging, but strategically vital approach is needed to address water distribution, invest in coastal resilience, mitigate climate change impacts, and support the vulnerable communities clinging to these vanishing shores before it's too late.

The writer is an expert on climate change and sustainable development and the founder of the Clifton Urban Forest. He tweets/posts @masoodlohar and can be reached at: mlohar@gmail.com