Today, the fishing village- turned trading centre that is Hong Kong consumes 2.5 million cubic metres of fresh water every day, more than enough to fill the Wong Nai Chung Reservoir (capacity 2.44m cubic metres), and a single person uses more than 112 litres of water a day. Last year, the cost of supplying water came to more than HK$5 billion.

To trace the dramatic, and sometimes distressing, history of water supplies in Hong Kong over the past 150 years is to understand the evolution of the city and its rapid urbanisation.

As the city grew in terms of population and industrialisation, so did the demand for water. The development of water supply was also linked with the need to ensure public health.

Besides serving these basic needs, the reservoirs of Hong Kong have also become a source of relaxation for those who like to go fishing. Last year, the Water Supplies Department issued more than 6,000 fishing permits with some conditions attached.

A dearth of natural resources, such as underground water and large lakes, meant there was never enough water in Hong Kong, not even in the early days of the trading colony when there were fewer people around than there are taxis on the roads today.

The thirst for water continued, resulting in awesome infrastructure projects, starting with the Pokfulam Reservoir, built when the population was reaching the 100,000 mark.

The tenure of a string of British governors saw engineers exploring a variety of sources from which to tap water.

As sites on land became scarce, reservoirs had to be carved out of sea inlets, such as the Plover Cove Reservoir (on the north shore of Tolo Harbour) and High Island Reservoir. Even a desalination plant had to be built, only to be abandoned a few years later.

Some of the water supply projects were recognised as major engineering feats. The Plover Cove Reservoir, with its 2,100-metre dam, is believed to be the first in the world to have been claimed from the sea.

The post-1850 period witnessed a rapid increase in the population, and demand from people and industry kept rising. The thirst for water increased at a rate of 6 per cent each year in the 20 years up to 1990. Per capita consumption was also on the rise.

Resources still proved insufficient, and Hong Kong had to turn to Guangdong for fresh water.

Today, water from Dongjiang, or East River, accounts for 70 per cent of the water supply in this global trading and financial centre. Dongjiang is expected to remain Hong Kong's biggest source of water for many years to come.

Dongjiang water comes at a cost and has sometimes caused public concern about its quality. But it is a secure supply. Even so, about 44 villages in the New Territories, with about 8,000 residents, have no water supply.

As the Water Supplies Department looks to the challenges of the future, it can take pride in its contribution to the city's social and economic development.

Hong Kong today has enough stored water to last six months. Water rationing - as in 1929 and 1963, when the city went dry - is a distant memory.

But needs keep growing. Major design works are underway on water projects, estimated to cost HK$10 billion, for the Cyberport and Disneyland.

A century and a half later, the city can boast of 16 reservoirs, 20 treatment works, 182 pumping stations, and about 6,400 kilometres of water mains.

Hong Kong has come a long way from those first five wells sunk in Central back in 1851.

Residents can raise a glass of water and take satisfaction in the thought of a scarce resource that has turned into a liquid asset.

Graphic: WATERgsp