All smelly and polluted rivers and waterways in Beijing will be cleaned up with the help of recycled water in three years, local authorities said on Tuesday.

Thousands of outlets discharging wastewater have contaminated 141 waterways in the capital, according to the Beijing Water Authority.

This year will see 24 waterways cleaned up in Chaoyang, Tongzhou, Haidian, Shunyi and Daxing districts. Another 33 waterways are scheduled for the cleanup program, according to the authority.

The capital has 425 rivers and waterways with a total length of 6,400 km.

"Last year, we started to build 76 wastewater treatment plants, and 45 have been completed with a capacity to process 950 million cubic meters of recycled water. This year, 1 billion cubic meters of recycled water will be processed to help clean up smelly waterways," Jin Shudong, director of the Beijing Water Authority, told a news conference on Tuesday.

Recycled water is reclaimed from sewage by removing solids and impurities and can be used to irrigate land, recharge groundwater aquifers, or meet other commercial and industrial needs.

By the end of the 13th Five-Year Plan (2016-20), the city is expected to have the capacity to produce 1.2 billion cubic meters of recycled water to improve the ecology, Jin said.

Meanwhile, the authority has built 1,290 km of pipelines to intercept and treat sewage, and another 1,181 km of pipelines are scheduled to be built this year.

Beijing is short of water resources, with only 150 cubic meters per person, less than half of the worldwide standard of 300 cubic meters, which shows the importance of reclaiming wastewater, said Jin.

For him, one key factor in the deterioration of water quality is the growing population. Three years ago, Jin visited Qinghe River in northern Beijing and, to his surprise, the river that was clean in 2008 had already become tainted, he said.

Before 2008, there were only 900,000 residents along the banks of Qinghe, but that number has tripled in five years and many pollutants have been discharged into the water, Jin said.

"Discharge and treatment facilities for polluted water lag behind the growth of population and have caused pollution," he said.