The Indus Delta, one of the largest deltaic ecosystems in the world, is facing severe degradation due to seawater intrusion. The consequences of this phenomenon include the submersion of millions of acres of land, increased salinity in groundwater, and a scarcity of freshwater resources, severely impacting agriculture and drinking water availability in coastal areas of Pakistan.

Seawater intrusion has resulted in the submersion of vast tracts of land in the Indus Delta region. According to a 2019 study by the Pakistan Council of Research in Water Resources, approximately 2.2 million acres of fertile land have been rendered unproductive due to seawater encroachment.

Historical satellite imagery and field observations indicate that seawater intrusion has steadily progressed inland, particularly in districts such as Thatta, Badin, and Sujawal, which were once thriving agricultural zones. Additionally, research from the National Institute of Oceanography (NIO) highlights that coastal erosion has accelerated due to the reduced flow of freshwater, resulting in a loss of over 10,000 hectares of mangrove forests, a crucial natural barrier against seawater intrusion.

The groundwater in coastal regions has become highly saline, making it unsuitable for both drinking and irrigation purposes. Research conducted by the NIO reveals that nearly 80 per cent of shallow groundwater sources in the Indus Delta region contain saline water exceeding the WHO safe limit of 500 mg/L of total dissolved solids.

The degradation of the Indus Delta due to seawater intrusion is pushing millions toward displacement and water insecurity

Furthermore, soil tests conducted in deltaic areas indicate a sharp increase in soil salinity from less than 4dS/m in the 1950s to over 15dS/m in recent years, making it nearly impossible to sustain traditional crops. Data from the Sindh Agriculture Extension Department indicate that 90pc of the coastal farms that once grew wheat, rice, and vegetables are now either abandoned or have switched to salt-tolerant, low-yield alternatives.

The Indus Delta historically thrived due to an abundant supply of fresh water from the Indus River. British-era records from the late 19th century indicate that the Indus River carried approximately 150 million acre-feet (MAF) of freshwater annually to the delta. However, following the construction of major dams and barrages such as Kotri Barrage (completed in 1955), the downstream flow to the delta has drastically reduced.

A study by the International Union for Conservation of Nature (IUCN) found that freshwater flow below Kotri Barrage dropped from 84 MAF in the 1960s to less than 10 MAF annually by the early 2000s. Furthermore, recent data from the Indus River System Authority indicates that in some years, freshwater discharge to the delta has been as low as 0.75 MAF, which is insufficient to counteract seawater intrusion and sustain deltaic ecology.

The construction of new canals has further exacerbated water scarcity in Sindh, particularly in coastal areas. The controversial Greater Thal Canal and Chashma-Jhelum Link Canal, designed to divert water for irrigation in Punjab, have significantly reduced water availability downstream.

According to official figures, the Greater Thal Canal was designed to withdraw 1.873 MAF annually, while the Chashma-Jhelum Link Canal has a designed flow of 21,700 cusecs. The reduced flows have severely affected the agricultural landscape of Thatta, Badin, and Sujawal, leading to a sharp decline in crop yields. Data from the Sindh Abadgar Board indicate that wheat production in lower Sindh has declined by 40pc over the past two decades due to water shortages.

Seawater intrusion has devastated agricultural production in the region. Once known for its rich rice and wheat cultivation, the fertile lands of Thatta and Badin have now turned barren due to increased soil salinity. Over 1.2m people, primarily small-scale farmers and fisherfolk, have been displaced from these areas as their livelihoods become unsustainable. A study by the Sindh Development Institute estimates that 70pc of the agricultural land in the delta is now unsuitable for conventional farming.

Additionally, data from the Pakistan Fisherfolk Forum show that fish production in the delta has declined by nearly 80pc over the past three decades, further exacerbating poverty and food insecurity in coastal communities.

The lack of freshwater inflow has led to a critical shortage of drinking water for the coastal population. Reports from the Sindh Irrigation Department highlight that the intrusion of saline water has forced many communities to rely on tanker-supplied freshwater, often at exorbitant prices.

A survey conducted by the World Wildlife Fund-Pakistan in 2021 found that over 75pc of households in the delta rely on external water sources due to the contamination of local wells. Furthermore, a 2022 report by the Pakistan Institute of Development Economics estimates that over 65pc of waterborne diseases in the region are directly linked to the consumption of saline or contaminated water, increasing the health burden on already marginalised populations.

The drinking water crisis is not limited to the coastal region; it is also affecting major cities, including Karachi, Hyderabad, and Thatta. Karachi, Pakistan’s largest city, depends on the Indus River for nearly 90pc of its water supply, primarily sourced from the Kenjhar Lake, which is fed by the Indus.

Historical records from the Karachi Water and Sewerage Board indicate that the city received 650m gallons per day (MGD) of water in the 1990s, but due to upstream diversions and reduced Indus flows, this supply has fallen to less than 500 MGD in recent years, despite increasing demand.

Similarly, Hyderabad and Thatta, which rely on the Indus, are facing similar shortages, forcing residents to depend on contaminated local sources, exacerbating public health crises.

The degradation of the Indus Delta due to seawater intrusion is a pressing environmental crisis. The reduction in freshwater inflows, rising soil and water salinity, and subsequent agricultural collapse have pushed millions toward displacement and water insecurity.

Immediate interventions, such as increasing freshwater discharge below Kotri Barrage, constructing seawater barriers, and implementing sustainable agricultural practices, are essential to mitigate further damage and ensure the survival of this once-thriving ecosystem. Furthermore, policies must incorporate community-driven solutions.

Dr Abdul Ghani Soomro, and Dr Aneela Hameem Memon are working as a principal and senior scientist, respectively, at the Water and Agricultural Waste Management Institute, Pakistan Agricultural Research Council, Tandojam.
Email: ag2005parc@gmail.com, aneelahameem@gmail.com

Published in Dawn, The Business and Finance Weekly, March 3rd, 2025