"When I first came here, there was only a forest with lots of wild animals, including lions," recalls Chairman Juma Omar Shindo, one of the earliest migrants to what became one of the largest urban sprawls in Tanzania's main city, Dar es Salaam. "All the forest belonged to missionaries then and what dwellings there were, were scattered far and wide."

It's hard to imagine such a scene from just over 50 years ago sitting in a tiny open office on a narrow dusty street in a small corner of the ever-growing Mbagala area.

Although Chairman Juma, a street leader for the neighbourhood of Bughdada, remembers people starting to build homes from the late 1950's in locations that are now fashionable parts of Dar es Salaam, it wasn't until the 1980's that he really noticed significant migration from Tanzania's rural areas.

"Up until then, there was no infrastructure. No roads, very few schools and clinics. There was no transport so people had to walk far. It would take us two days to walk to the hospital where there was only one doctor. Water, we would buy from a pump but then we paid cents, now we pay in shillings," he reminisces.

Decades later, there are still issues over lack of infrastructure, particularly clinics, dispensaries and schools. But although these refrains are repeated by residents across Mbagala, the most common one is for water in a city unable to meet the demands of a rapidly growing population.

Mbagala alone has an estimated population of about 200,000 though nobody really knows. Ninety per cent of its residents are migrants from other parts of the country.

The story is similar elsewhere in Dar es Salaam. It's rare to come across anyone in the city that is actually from there. Officially, the former Tanzanian capital has a population of about 2.7 million people but it's widely estimated to be above 4 million and rising.

Mary, a social worker who came from Kilimanjaro region 10 years ago, has to get her water from a well 500 m from her home. Each bucket she carries back costs her 30 Tanzanian shillings (US 3 cents per bucket).

"Getting water now is so much more difficult than before. Then we used to have piped water coming to the house. We used to pay 8,000 shillings a month for it. Then it stopped coming," she says. She thinks the pipe infrastructure broke down and was never repaired. Like many others, she buys her water from someone who has dug a well with no checks on the quality of the water she and others are using.

Anna, who came to Dar es Salaam nearly two years ago with her husband and children after they could no longer scrape a living growing and selling vegetables in Tabora, western Tanzania, can at best only afford five buckets of water a day.

With a husband unable to work and in poor health and the family of five living in one tiny room with no electricity, Anna struggles to keep the family afloat. Five buckets of water at a total cost of 15 US cents a day for drinking, washing and cooking in a country where millions of people are living on less than one dollar a day is a significant amount of money.

In plush areas of the city including the diplomatic neighbourhood, where the cost of water is not so much of an issue, water has to be trucked in.

Demand for water is about 450,000 cubic metres a day, but the Dar es Salaam Water and Sewerage Authority (DAWASA) that supplies the city can only provide 270,000 cubic metres.

According to its Chief Operation Officer Jackson Midala, the authority had previously predicted a population growth of 3 per cent a year for the city. Instead, the current growth is 8 per cent.

It's dependent on its supplies on surface and underground sources, primarily two water treatment centres along the River Ruvu.

But the river doesn't have the amount of water it used to have and its flows are less reliable than they used to be. The rains that used to come twice a year now only appear once.

There are other knock-on effects of dropping water levels for a country dependent on hydro-electricity. River levels had dropped so low in 2007 that electricity supplies to Dar were badly hit, forcing rationing which in turn affected businesses and tax revenues for the government.

As well as the changing weather patterns, DAWASA has other challenges to deal with.

Population growth has gone handin- hand with large-scale unplanned construction, posing particular difficulties for the water authority in areas where there is no existing water infrastructure.

"The solution to the problem would be to build a dam on the Ruvu in order to store excess water from a good rainy season," says Midala. But a plan to build a dam at Kidunda in a game reserve had costs to both the wildlife and to people living there who would have lost their land. It didn't take off.

The authority realizes that the River Ruvu is a finite resource and doesn't want to tap underground water due to environmental implications but its options are limited. Less rainfall and growing demand for an increasingly scarce but vital resource means there is little choice.

Work is about to get underway to drill 20 deep wells that can produce 260,000 cubic metres a day while the lower Ruvu treatment plan will shortly be expanded to increase output by nearly 90,000 cubic metres a day. The Norwegian Embassy is also funding a USD 6 million research project on the sustainability of tapping a deep water aquifer that could help meet some of the city's water needs.

Although Dar es Salaam is home to 10 per cent of the country's population, other parts of Tanzania are also being hit by the uncertain access to water with implications for further out-migration from rural areas.

In towns like Arusha in the north which has also seen an explosion in population growth unaccompanied by proper town planning and resource management, farmers and agricultural workers are already at the sharp end of climate change and environmental degradation.

The snows of Africa's tallest mountain, Mount Kilimanjaro, have long been an iconic image of East Africa. But now, even on a clear day, it's hard to see much snow. In the past century,

Its fertile lower slopes and surrounding lands are famous for its banana and coffee plantations. But locals say these crops are no longer doing so well. The weather has changed though soil erosion and lack of irrigation systems also play their part.

A local priest and lifelong resident of Moshi, the main town in Kilimanjaro region, says people are not able to earn as much as they used to and livelihoods could disappear. The easy option is to leave for the cities in search of work. Droughts, crop failures and environmental degradation have already led to some farmers from Tanzania's more arid areas to leave their land in search of the city's bright lights. Only to find that water is as much an issue there as it was back home.