ISTANBUL (AFP) - Burgeoning population growth, poor resource management and floods and droughts amplified by climate change hamper efforts by Asian countries to provide clean water and decent sanitation, the World Water Forum heard Friday. Ministers from major Asian nations, in Istanbul, admitted they faced a major challenge in trying to meet surging demand for freshwater while at the same time conserve it. Chinese Water Minister Chen Lei said his country's population, the largest in the world, had to grapple with water wealth that was unevenly distributed and sometimes sparse. The mismatch "gives rise to intensive conflicts between socio-economic development, water resources and the water environment," he said. The Asia-Pacific occupies 61 percent of the world's population, but its water resources only account for one third of the global total, according to a report issued at the meeting. Half a billion people in the region still lack safe drinking water and 1.8 billion are without access to basic sanitation. Of the available sources of renewable water, 79 percent is used up by agriculture. In some of Asia's breadbaskets, such as the Punjab in India and the North China plain, unreplenished extraction is causing water tables to fall by between two and three metres per year, while the glaciers in the Himalayas are shrinking faster than in any part of the world. All this amounts to a grim outlook for farming, food security and access to safe water and sewerage, the report said. "At its most dire, the region's water circumstances set the scene for tragedies and unfathomable suffering on a daily basis," it warned. Bangladesh Water Minister Ramesh Chandra Sen said his country faced "daunting challenges." "Every year, abundance of water during the monsoon causes disasters like floods and river bank erosions, and scarcity of freshwater during the dry season causes salinity ingression, drought," and other problems, he said. Added to that was contamination of groundwater, drawn from shallow tubewells, by naturally occurring arsenic, he said. Health experts say as many as 70 million people in India and Bangladesh are exposed to excessive concentrations of arsenic and fluoride. Some experts describe it baldly as the biggest mass poisoning in history. Indonesia's minister of public works, Djoko Kirmanto, said countries in Southeast Asia were already beginning to be affected by climate change, which was affecting rainfall patterns and harvests. "Recently, severe water-related disasters, such as floods, droughts, tsunami, rainstorms, landslides, water-borne diseases and epidemic have occurred in high intensity," he said. Ministers outlined national water programmes, in water supply and conservation and flood control, and promised to work in regional fora to address competition for water supplies. China's Chen defended his country against accusations of water misuse and pollution. Greens point to problems of over-extraction of aquifers and river pollution, and say the Three Gorges dam and programmes to divert water towards the dry north of the country could unleash ecological disaster. "Over the past 30 years, China has sustained a nearly 10 percent annual economic growth rate at a one percent annual growth rate of water use," Chen said. "By 2020, when an all-round, well-off society becomes a reality in China, the Chinese people will be safely protected from floods, have access to safe and clean drinking water in both urban and rural areas (and) enjoy (a) remarkably improved water environment." The World Water Forum, wrapping up on Sunday, has drawn around 27,000 experts, policymakers and activists to round tables, seminars and debates on the worsening problems of freshwater.