South Asia: Water surpluses to persist in Ganges and connecting basins

September 19, 2016

The Big Picture
The 12-month forecast map (below) shows the presence of water surpluses in northeastern Afghanistan, central India, Nepal, Bangladesh, and Myanmar’s western coast. Water deficits are forecast for western Afghanistan; western Pakistan; and Gujarat, Tamil Nadu, and Odisha, India.

Impacts
Officials at India's Central Water Commission have stated that flooding on the Ganges River this year surpassed previous records, reaching the highest level - 50.52m (166ft) - in Patna, Bihar on 26 August. More than 150 people have died.

Protests became violent in India's southern state of Karnataka as the country's Supreme Court ordered the state to release 12,000 cubic feet - almost 90,000 gallons of water - per second from the Cauvery (Kaveri) River until September 20 to neighboring state Tamil Nadu. Public gatherings were banned, a curfew imposed, and riot police were called in to quell disorder in Bangalore (Bengaluru) as protesters set fire to vehicles and damaged buildings. One protester was killed by police and 78 vehicles were burned by rioters. Companies in Bangalore, the country's IT hub, lost an estimated Rs 22,000-25,000 crore (US$3.3-3.75 billion) during the four days of disruption according to the Associated Chambers of Commerce and Industry. The Karnataka State Natural Disaster Monitoring Centre recorded a 29 percent rainfall deficit in August for the Cauvery catchment.

Reports indicate that, after two consecutive seasons of drought, India - the world's second largest producer of sugar - will become a net sugar importer due to estimated production losses of 3.7 million tonnes.

Forecast Breakdown
The 3-month composites (below) show the evolving conditions. Evident in the map series, water surpluses ranging in severity from moderate (5 to 10 years) to exceptional (greater than 40 years) are expected to continue to emerge through May through southern Rajasthan along the Chambal River and its tributaries, eastward to the Yamuna River, to the Ganges River, and into Bangladesh.

Moderate to extreme (20 to 40 years) water deficits are forecast September through November in western Afghanistan and western Pakistan. In India deficits are forecast in Karnataka, Kerala, and western Tamil Nadu, with lesser deficits in eastern Maharashtra, Gujarat, and from Delhi north to Himachal Pradesh. Exceptional surpluses are forecast September through November in Bangladesh and Myanmar’s western coast. Surpluses in Bangladesh are expected to persist through May, though the extent of exceptional surpluses will shrink. Myanmar’s western coast will transition to both deficits and surpluses from December on.

As seen in the December through February map, deficits in Gujarat are forecast to become more severe with small pockets of exceptional deficits on the western edge of the Gulf of Khambhat. Both deficits and surpluses are forecast northeast of Gujarat as deficits emerge in areas of recent surplus along tributaries of the Chambal River in Rajasthan. Moderate to severe (10 to 20 years) deficits are forecast to emerge during this period in Assam and surrounding states in northeast India.

The overall pattern of the forecast for March through May is similar to that of the prior three months.

(It should be noted that forecast skill declines with longer lead times.)