“Frankly speaking, the demand-supply gap is huge: demand is 400 million liters a day. Supply varies from 90 to 150 million liters,” said Sanjeev Bickram Rana, the executive director of the Kathmandu Valley Water Supply Management Board. “How can we bridge that gap?”

The roads in the area also impede water delivery to residents. Most trucks source their water in places like Khahare, where the terrain begins its slow climb to the Himalayas. But the rural roads are so rough that they can’t drive fast for fear of snapping axles, and the city’s poorly designed transport network is frequently snarled with traffic. Businessmen say their trucks could perform double their current daily average of four deliveries and thus sell more cheaply if they could move quicker. But with no expectation of improved roads, tanker drivers have implemented their own precautions.

Some pad their ceilings with folded newspapers to cushion the blows as they get bounced around their suspension-less vehicles; others deck their cabins out with so much religious iconography they can scarcely see through their windshields. The most impatient, or those who work the most traffic-clogged routes, take things further. Many trucks have equipped themselves with mini TVs or booming sound systems.

The government’s proposed solution to these grave water shortages, the Melamchi project, has turned into a four-decade-long fiasco of almost unrivaled incompetence. First proposed in the 1970s and begun in 2000, this scheme to divert a mountain river from the Himalayas has been so delayed that the water it will bring — 170 million liters a day in its first phase — is already insufficient to cover half of Kathmandu’s needs. It’s not a good plan, anyway, experts say. The pipeline network is so riddled with holes that “you could have Lake Baikal on the other end and it still wouldn’t be enough, ”Mr. Gyawali said.

In an interview at her family’s tightly guarded compound, Bina Magar, the minister of water supply, blames her predecessors for the severity of the water deficit. “For so long we had unstable governments that have lasted one year, six months, eight months.” she said. “Now we have an opportunity to bring stability and fix everything.” And while the minister conceded that tankers have helped mask the state’s shortcomings — so much so that every ministerial residence relies on them — she insists they’re living on borrowed time. “They charge too much. We charge much less. Once Melamchi is complete, we will be the answer.”

But corruption and bureaucracy riddle almost every level of state, ensuring the tankers perform even worse than they otherwise might. Tanker men field so many demands for bribes that they sometimes keep wads of cash on hand for that purpose. If they don’t pay sums that vary from 5,000 ($43) to 100,000 ($866) rupees, they can get shut down, a dozen businessmen said. These costs, too, must be passed on to the consumer. Officials are noticeably tentative in their denials. “These claims are not related to our organization, but perhaps the traffic police or someone else,” said Mr. Rana of the water management board, citing what’s widely seen as the greediest branch of Nepali officialdom.