Lingering pollution problems in East China's sprawling cities and counties have stretched the budget for the eastern route of the country's South-to-North Water Diversion Project and added to the difficulties inherent in maintaining the quality of drinking water in the north, a senior official has said.

Efforts to control pollution along the 1,400 km-route have run into new obstacles, largely because of population growth and industrial expansion in counties and townships along the route, Lu Zhenlin, office director in charge of the construction of the program's eastern route in Jiangsu province, told China Daily.

As a result, more projects have to be adopted to clean up the waterways, he said.

"Since the projects concerning new pollution sources are not included in the project plan that was devised a decade ago, we had and still have to invest more money in them," said Lu, without revealing how much more has been spent.

"This is crucial to maintain the quality of the drinking water to the north, and we need to continue doing this, given that pollution may worsen with economic growth," he said.

"But we're confident that the eastern route will meet quality standards and become operational by 2013."

The project, the largest effort of its kind in the world, will take water from the water-rich Yangtze River and divert it to the dry north. The beneficiaries will include Beijing and Tianjin, as well as scores of other drought-prone cities along the project's three routes - the eastern, central and western water diversion channels, which each stretch for more than 1,000 km.

The investment in the massive program is estimated at 500 billion yuan ($76 billion), dwarfing that of the Three Gorges Project, which stood at about 200 billion yuan.

Still, E Jingping, the top official at the office in charge of the South-to-North Water Diversion Project, warned at a recent conference that total spending on the project might exceed the budget for reasons that include inflation and possible adjustments to the project design.

Of the 155 sub-projects related to the South-to-North Water Diversion Project that were planned for past years, only 33 were completed; work on 31 others was not brought under way as scheduled. That meant that only about one-third of the money that was supposed to be invested actually was, and that the remaining two-thirds will have to be spent before the eastern route becomes operational in 2013.

The eastern route runs through major industrial regions, including Jiangsu and Shandong provinces, where two decades of rapid economic growth have left the rivers and lakes there more polluted than those in Central and West China. Officials now believe that controlling pollution will be fundamental to the success of the project.

In the original plan, the eastern route, brought under construction in 2002, was scheduled to open in 2008. Media reports have blamed the delays on water quality troubles and soaring costs.

So far, 20 percent of the monitored cross sections along the eastern route have not met mandatory water quality standards, even though most of the pollution-control projects have been finished, official statistics showed.

Lu also dismissed seawater desalination as an alternative to the water diversion project, saying desalination will "bring potential damage to the ecological balance of the sea".

"When condensed salt is returned to the sea, it would change the ecological environment. Also, the cost of seawater desalination is too high of a barrier."

"But we do need to come up with plans to prevent the exploitation of the Yangtze River by local governments, some of which have set up too many dams along the waterway," Lu said.