“Ciliwung River is the most polluted river in the country both in upstream and downstream areas,” Hermono Sigit, head of river unit at the ministry told reporters on Tuesday.

The 119-kilometer-long Ciliwung River has 60 percent of its length in West Java province with the remainder in Jakarta. Millions of people live along its banks and depend on the water source for laundry and washing.

The samples of water taken by the ministry in its 2009 study showed the level of E. coli bacteria of upstream Ciliwung in Atta’awun in Bogor was about 900,000 per liter.

The E. coli density increased downstream with samples at Manggarai showing 790,000 E. coli per liter and those at Ancol Marina holding 110 million per liter, the study says.

He said pollution in upstream Ciliwung was due to the high levels of domestic garbage and waste from agricultural activities being dumped into the river.

“In Ciliwung’s downstream area in Jakarta, pollutants of biochemical oxygen demand [BOD], chemical oxygen demand [COD] and E. coli continue to increase,” he said.

The ministry submitted a draft of a presidential regulation on the rehabilitation of Ciliwung River in 2009.

“We hope to finish the draft of the presidential regulations for another three rivers — Citarum, Cisadane and Progo— this year,” he said.

The Citarum runs about 225 kilometers in West Java province, Cisadane runs 80 kilometers from West Java to Banten while Progo River runs 338 kilometers from Yogyakarta to Central Java.

Environment Minister Gusti Muhammad Hatta earlier said it would take 20 years just to restore water quality in Citarum River at an expected cost of Rp 35 trillion.

The ministry said that forested land now covered only 1.4 percent of the Citarum River basin, far less than the minimum requirement of 30 percent as stipulated in the 1999 Forest Law.

In 2009 the total forested area had been reduced to 9,899 hectares from 71,750 hectares in 2000. The same period saw residential areas more than double to 176,442 hectares from only 81,686 hectares in 2000.

Data from the ministry said that others priorities of rivers were 775 kilometers Batanghari River in Jambi and West Sumatra, Kampar River in Riau and West Sumatra, Musi River in Bengkulu and South Sumatra, Siak River in Riau, Bengawan Solo River in Central Java and East Java, Brantas in East Java, Citanduy Rivers in West and Central Java, Barito in Central and South Kalimantan and Saddang Mamasa in West and South Sulawesi.

Surabaya-based environmental activists, the Ecological Observation and Wetland Conservation (Ecoton) has threatened to take legal action against the government over the poor quality of water in Brantas River.

Executive director of Ecoton Prigi Arisandi demanded President Susilo Bambang Yudhoyono and the Environment Ministry to improve the quality of Brantas River within 100 days.