Understanding the Kathmandu Valley: What has been learned in decades of water systems, what are pressing questions, and how to put it to use

In 2014, an Italian company hired to complete the tunnel abandoned the project, accusing Nepali bureaucrats of pressuring workers for bribes. Sinohydro, a Chinese company, finished construction in March 2021.

Then disaster struck. The start of testing was interrupted by a flood. The water flowed for only six weeks before the flood and landslide struck.

The idea of supplying the capital city with drinking water was first floated in the 50’s, and with Nepali taxpayers still on the hook for $420 million in loans, it’s no closer to happening.

“We are worried that if rainfall is above normal, then this kind of disaster may happen again,” said Rajendra Sharma, a hydrologist and the government’s technical adviser on the Melamchi project.

When Gaurab K.C., an assistant professor of sociology of law, was growing up in Kathmandu, the annual monsoons brought a nightly chorus of croaking frogs and jasmine-perfumed air.

But many of the wetlands and rice paddies that absorbed the monsoon rain and topped up the water table have since been paved over, as the Kathmandu Valley urbanized at one of Asia’s fastest rates, with its population rising from over half a million in 1991 to more than two million in 2021.

Like most people in Kathmandu, Mr. Gaurab relies on an elaborate system to catch, collect and buy enough water for his household. He uses two rooftop tanks of rainwater for washing and plumbing. He buys additional supplies from water tankers for washing vegetables and drinking.

Bangladesh has shown the political willingness to tackle its challenges around water insecurity. Increasing funding for infrastructure is one of the things that success will depend upon in the future, as is a more-comprehensive understanding of the water systems.

Satellite and local data reveal risks when analyzing water resources. Here we set out what is known, define pressing questions and describe how to put that knowledge to use.

An Earth Information System to Assess the Impact of Climate Change on Bangladesh’s Water Supply and Flows: Data Requirements from India and Pakistan

Bangladesh’s gross domestic product has increased eight-fold since 2000, making it one of the fastest-growing economies in the world. To encourage food security, the government has promoted agriculture. This has brought farmers to cultivate rice in the dry season as well as in the wet season. Rice productivity has doubled since 1990. Bangladesh produces rice at a higher rate than other nations such as India and Thailand, with Rice perhectare increasing by 29% over the last ten years.

Over the past few decades, Bangladesh has benefited from World Bank initiatives, in partnership with local authorities, which have added thousands of cyclone shelters and water-control structures, several thousand kilometres of dikes and hundreds of polders. More than three quarters of a million people are now protected from tidal flooding and storm surge. More investments are needed to protect against the increasing risks posed by climate change.

All of these efforts require good data to inform understanding of water supplies, flows and forecasts, so that the right infrastructure can be built in the right places.

Bilateral collaboration between Bangladesh and water-sharing nations, such as India, would be beneficial. The decades-long Mekong River Commission between Cambodia, Laos, Thailand and Vietnam is one successful transboundary agreement that could serve as a model.

NASA’s Earth Information System launched in 2021, is one of the new open-science initiatives that can help with the development of data-analysis and modelling tools. This framework was used to acquire the data we present here. We are trying to develop a model that can show how climate change affects Bangladesh’s water availability. We expect that the co-development of such a modelling system with local partners will support decision-making.

It is possible that the SERVIR programme can improve the forecasting of severe weather for Bangladesh. This could improve the flood monitoring and forecast system operated by the Bangladesh Water Development Board, which is limited in geographical scope — flooding is monitored only at specific locations, not across the country. Such efforts will help with short-term adaptation and emergency responses to flood conditions, and with long-term planning for infrastructure.

Satellite-based systems can be used to determine the volume of water actually needed by crops. One of us helped establish a system in northern India and eastern Pakistan. This was developed at the University of Washington in Seattle, in partnership with the Indian Institute of Technology in Kanpur and the Pakistan Council of Research in Water Resources in Islamabad. They estimate that such a system could save more than 200 billion litres of groundwater annually in these two regions combined9. This is a small proportion of the total demand for water for irrigation, but would be enough to supply, for example, about 4–5% of Bangladesh’s domestic water needs.

These irrigation advisory systems could be improved further by increasing the spatial resolutions of input data — some of which currently come from coarse-resolution global forecast models — and doing further validation on the ground.

Another strategy is to adapt to sea-level rise and incursions of salt water. Many farmers have stopped cultivating oilseed, sugar cane, and jute because of rising salt levels on the coast. Local fish species can’t tolerate salty conditions, which has caused conflict between fish farmers and rice farmers. Adding brackish aquaculture of non-local species of fish would help this system.

Several salt tolerant plants, such as Atriplex species, tamarisk and mangrove are commercially available and can grow well in coastal areas. As well as providing food and fodder, these plants have the capacity to desalinate soils. It is a good idea to conduct research to assess the suitability of them for Bangladesh.

Inform about the fight against it. A centralized sewerage system is likely to be too costly for Bangladesh and is only viable in the long term. For now, many urban residences have simple, low-cost septic tanks on site. Most of the time they are not designed and constructed to release partially treated effluent into surface waters. Researchers can help by assessing the financial costs of water quality monitoring systems to help governments understand trade-offs.

Efforts to remove arsenic from the environment include piping clean surface waters or helping people to switch to lower arsenic sources. Low-cost, real-time monitoring systems would be greatly aided by these efforts.