At first light in Tanzania's main city Dar es Salaam, some of its six million residents begin their day with a frantic search for water.

Christmas is approaching, but the festive mood is dampened by the dry pipes, as the city experiences serious water shortages.

In some homes, plastic containers are stacked outside the door, ready to be carried at a moment's notice whenever word spreads that a nearby tap is flowing again.

City authorities ration water. Homes get it once a week, but the wait can stretch for weeks for some families. The crisis, caused by a drought and rising demand, has persisted for months.

Many people are forced to turn to private vendors, who source their water from boreholes and tanks. They are a respite for thousands of families, but their high costs are a heavy burden to low-income households.

Cedric Ndosi, who lives in Madale, north-west of the city, plans to host guests for lunch on Christmas Day, but he is worried.

"Christmas is here and there is no water in our taps. We are forced to buy water from shops for cooking and from water trucks for bathing, but it's expensive.

"We were used to spending money on drinks, but now even water for cooking has become an added cost," he adds.

Furaha Awadhi, a mother of two living in Tegeta on the outskirts of the city, says the price of water has risen from $4 (£3) for 1,000 litres to $10.

Cedric Mushi, who lives in Ubungo, west of Dar es Salaam, says that whenever the city authorities switch on the taps, he makes sure that he stores water so that her family does not suffer.

"It comes only once a week, usually in the late hours of the night," he says.

As a result of the prolonged dry spell since the end of the rainy season in May, the water levels in rivers and groundwater that the city depends on has sharply reduced, officials say.

The authorities say this has forced a cut in supplies from water treatment plants. They also blame leaking pipes in the distribution network, leading to water being lost.

Dar es Salaam, on the Indian Ocean coast, is among Africa's fastest-growing cities. Over the past two decades, its population has more than doubled as an increasing number of people move in, looking for better economic opportunities.

New neighbourhoods have spread far beyond the city's original boundaries, and even in good times, the available water supply could barely serve its inhabitants.

For the festive season, Joyce Fredrick is planning to escape the heat and the inconveniences of having no water.

"Here in Dar es Salaam it's extremely hot, no rain, no water. We are going to Arusha (in the north), where at least the weather is more friendly," she tells the BBC.

Unlike many other major Tanzanian cities, Dar es Salaam has been particularly vulnerable to the failure of the October to December rainy season.

Even Dodoma, which often receives little rainfall throughout the year, is less affected thanks to its man-made dams.

In contrast, Dar es Salaam lacks a nearby freshwater source, is heavily populated, and experiences some of the country's highest temperatures, currently averaging around 33 °C.

Although it is next to the sea, there is no desalination plant to make the ocean water usable for residents.

Much of the city's drinking water (about 70%) comes from the Ruvu River, whose flow is closely linked to seasonal rainfall inland.

Smaller volumes are drawn from other rivers and from sources such as boreholes, but these provide only limited relief when rains fail.

When the Ruvu's flow drops, as has happened this time, the effects are felt almost immediately, especially in high-lying areas and newly developed suburbs of the city.

The impact is widespread but uneven, depending on a household's economic status.

People have invariably adapted to the uncertainty: some stay awake until morning not to miss the rush of water in their pipes, others line their rooftops and courtyards with containers to store every precious drop of water from the little rain that falls.

For small business owners, the crisis has become an acute strain. Some food vendors, salon operators, and car wash businesses have cut back hours or raised prices.

Women are often seen looking for water for their homes.

"When water is scarce, everything else stops. At times hygiene suffers, stress increases, especially for us mothers, and the whole household feels the impact," says Tegemeo Kombe, who lives in Kibamba, west of the city.

The government has acknowledged the severity of the problem. Water Minister Juma Aweso told the BBC that Dar es Salaam's dependence on rainfall-fed rivers had left it particularly exposed.

"Longer-term solutions are under way, we are in the process of building a dam that will collect water from different fresh water sources to solve the problem in future," he said.

Aweso added that investments in the drilling of more boreholes will help meet future demand and protect the city against climate shocks.

The Dar es Salaam Water and Sanitation Authority (Dawasa) has apologised to residents for the disruption in their lives, and has appealed to them to conserve water.

Critics however have called for better communication, clearer rationing schedules and faster implementation of long-promised projects.

And while some are concerned that water shortages risk becoming more frequent, Ms Fredrick is hopeful that the situation will improve.

"When water is missing, life changes too," she tells the BBC. "We believe things will be better next year."