BUYAN, Indonesia (Reuters) - Every year since 2000, the water level of Bali's Lake Buyan has been falling, leaving many locals puzzled.
Some believe deforestation in the surrounding mountains is to blame, while green groups suspect the shrinking lake is emblematic of looming water shortages the Indonesian island is likely to face as more and more tourists visit.
"I don't know why but it looks like the trees have been cut down," said vegetable farmer Nyoman Suarjaya, standing near an embankment now several hundred metres from the lake's edge.
"So there's no water catchment," he added.
He pointed to a pavilion built a few years ago for tourists to launch canoes onto the lake. It now lies abandoned near an expansive stretch of land that once used to be the lake bed and now has become fields for vegetable growers.
Lake Buyan, one of Bali's deepest, no longer draws tourists, just locals curious to see the receding lake which has faced a 3.5 metres drop in water levels since 2000.
In the densely populated south of Bali, tourism and the construction industry are fuelling a boom in the island's economy, which serves as a regional business hub.
About two-thirds of Bali's 3.5 million people live in the main city Denpasar and further south to the tourist areas of Seminyak, Legian, Kuta and Nusa Dua, where environment ministers are meeting this week to try to agree on the outlines of a broader pact to fight global warming.
Tourism has rebounded this year after a series of bomb blasts. The recent construction boom involving factories, malls, luxury villas, spas and high-end resorts has led to ever-greater demands for water, electricity and waste management.
But some parts of the island, named in a recent Travel + Leisure magazine poll as the world's best, are already facing water shortages or salt-water intrusion into wells.
Environmentalists and some government officials say the problems could become worse unless significant investment is made and people started conserving water.
"If there's no change in this fast-growing tourism development, it's not impossible that Bali will suffer from a water crisis in the next 10 years," said Agung Wardana from Wahli, a leading Indonesian environment group.
"The current emphasis is the development of the tourism industry which results in changes in productive and open lands that reduce the ability to provide ground water. This is made worse by neglect of river system," he added.
ALL IS NOT WELL
Many Balinese rely on wells for water but in some areas, particularly in the tourist centre of Kuta, so much is being extracted that salt water is fouling supplies. Rubbish and sewage being dumped into rivers was also affecting water quality.
Bali has few reservoirs and many of its rivers are used to channel water to an intricate traditional network of channels to feed the island's iconic emerald rice fields.
"Since the development of tourism industry is very fast, in the future we will have a big problem," said Ida Cakra Sudarsana, head of the mining and energy division in the Bali Department of Public Works.
He said Bali's problems were not lack of ground or river water but one of development and he urged an expansion of reservoirs and tree-planting schemes in Bali's volcanic mountains to curb deforestation and water-conservation schemes.
"We're supposed not to face a water shortage until at least 2025," said Raka Dalem, a senior lecturer in environmental management and ecotourism at Bali's Udayana University.
"But in actual situation we do face a shortage situation because of bad management of water resources.
"During the wet season, lots of water flows to the sea and then in the dry season we face a bad problem. That's the main issue, how we manage the water so that it can be used throughout the year," he said.
While tourist businesses and farmers diverting water from Bali's lakes were partly to blame, there was also significant damage caused by the felling of forest trees near catchment areas for cash crop cultivation, experts said.
A lack of trees meant water and silt rushed into the lakes during downpours but there were less regular river flows during the dry season. It also meant that water was not being absorbed into the ground to fill underground basins that will provide for Bali's water needs in the future.
Water conservation is crucial.
Already at Nusa Dua, an enclave of five-star hotels and a major conference centre, the government has banned deep-well water. All big hotels in Nusa Dua used recycled waste water for watering gardens.
Many luxury villas also used water-recycling systems, said Nils Wetterlind of ecovilla developer Tropical Homes.
But most villas also have large swimming pools filled from well or town water. And very few villas used solar/natural gas electricity systems now widely available or used certified plantation timber, meaning they weren't very green.
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