IAIA 16 Nagoya, Japan 6 υ A paper presented at 36th Annual Conference of the International Association for Impact Assessment (IAIA 16), Aichi-Nagoya, Japan, 11-14 May 2016. Evaluation of water quality status of Ciliwung River based on Pollution Index Hefni Effendi Centre for Environmental Research, Bogor Agricultural University, Indonesia Abstract Pollution index calculation was based on Indonesia Ministry of Environment Decree No 115/2003. River water quality standard referred to Government Regulation No 82/2001 including 4 water quality classes namely class 1 for potable raw water source, class 2 for water sport and recreation, class 3 for fisheries and animal husbandry, and class 4 for irrigation. River water quality measurements were performed at various locations representing upstream (Bogor) and downstream (Jakarta) of Ciliwung River. Those sampling site were Katulampa, Kampung Kelapa, Jembatan Panus Depok, MT Haryono, and Manggarai. In general, river water quality of Ciliwung improved from 2012 to 2014. Highest pollution index existed at MT Haryono Jakarta downstream of Ciliwung, whilst the lowest pollution index occurred at Katulampa upstream of Ciliwung. At year 2012, Ciliwung river water quality status for class 1 (as raw domestic water source) was highly polluted. Meanwhile, at 2014 the status underwent improvement to be fairly polluted. If the purpose of Ciliwung river water quality referred to class 3 (fisheries and animal husbandry purpose), so at 2012 river water quality status was fairly polluted. However at 2014, improvement was revealed by the change of river water quality to be lightly polluted. The government is now having a continuous program of monitoring water quality of main river throughout the country. The data have been reported yearly to the Ministry of Environment and Forestry. These data series are worthwhile for setting up measures to be taken in resolving the problem of river water quality deterioration. Key Word: Pollution index, water quality standard Ciliwung River, water pollution. Introduction The water quality of rivers in Indonesia in general have exceeded water quality standards set out in Regulation 82 of 2001. More than 50% of monitoring points have been heavily polluted status. Monitoring points with heavily polluted status from 2009 to 2013 is likely to increase. Within five years of monitoring, water quality in Indonesia tends to decrease.