Erosion. Citarum River Basin is divided into 19 watershed areas with erosion levels ranging from extremely low to extremely high categories. The worst erosion occurrence is found in Citarum watershed with an annual erosion level of 592 tons per hectare.
Landslides usually happen in a slope of more than 2 m high and an inclination of 50%. Farmers in upper Citarum regions still prefer to grow vegetable plants of a short crop cycle. This practice prevents a speedy water absorption into the ground as the plants do not have prop roots which are capable of protecting the soil from erosion.
Erosion Rate in the upper Citarum area is higher than the level in the middle and lower Citarum. The high erosion level at the upper part of Citarum produces sediments which are carried away by the stream to lower areas.
Erosion Rate in downstream Citarum area is considered to be lower than the level at upper Citarum. Sub-watershed area of Cikao has a high erosivity level covering almost 6% of the total sub-watershed area (22,072 ha). Cikao sub-watershed, which is located in Karawang and Purwakarta Districts, is a hilly area which makes it prone to land degradation that triggers a high erosion level.
Sedimentation. A rising rate of erosion has contributed to the deposition of sediments into riverbeds, dams and even to water system infrastructure. According to the 12 January 2010 report made by the secretariat for Citarum Basin water resources management coordination the sedimentation rate in Saguling Dam reached 8.2 million m3 a year (in a 1988-2009 period), Cirata Dam 6.4 million m3 a year (1988-2008) and Jatiluhur Dam 1.6 million m3 a year (1987-1997). These high sedimentation rates would speedily reduce the dams’ capacities and shorten their operational lifespan.
Sediments deposited in lower Citarum area are contributed by erosion materials from upper region.
Bandung Groundwater Basin has been sinking. In a period of 2000 to 2002 the land area subsided by 7 cm to 52 cm in depth at a rate of 2 to 18 mm per month. This was in line with the rapid development in industrial and public settlement expansion. Therefore, the most severe decrease in groundwater level was recorded in industrial areas such as Cimahi (around Leuwigajah), Batujajar, Dayeuhkolot, Rancaekek-Cicalengka, Ujungberung, Cicaheum, and Kiaracondong. In 2008 the demand for water for domestic, industrial and irrigation purposes was estimated to reach a total of 17.6 billion m3 per year. This demand for water is expected to rise at a rate of 1 to 1.7 % a year and only a half of the total demand can be fulfilled by a surface water supply, while the rest will be covered by groundwater sources.
Groundwater Exploitation. Within Bandung area, 90% of the total population and 98% of the industrial activities rely on groundwater sources. Groundwater exploitation, however, leads to land subsidence and decreasing groundwater level especially in Bandung Basin area. The groundwater level at a certain same location has reportedly dropped by 5 m in depth per year with a total accumulative decrease of 85 m in depth over the last 80 years. Today, a manufacturer needs to drill up to 150 m deep into the ground to access groundwater. Citarum River Basin is home to about 1,423 manufacturers. The expansion of manufacturing industry especially in Bandung area and lower Citarum leads to an increase in water consumption. Inadequate supply of surface water sources raises the practice of overexploitation of groundwater by the industry.
Population growth and rapid expansion in infrastructure and facility developments in Citarum River Basin affects the environmental condition, resulting in environmental quality deterioration, environmental degradation and destruction, natural resources depletion and land use conversion.
Land Use Conversion over a period of ten years (2002-2012) was materialized in the land use expansion for housing to 83.35 km2, fish pond 40.67 km2, farm 28.24 km2, industrial activities 24.74 km2, garden/plantation 21.43km2 and bush 13.02 km2. While land use for forest was reduced to 131.18 km2, irrigated rice fields 38.56 km2, mangrove forest 27.97 km2, rainfed rice fields 5.85 km2, salt ponds 4.11 km2, swamp areas 2.08 km2 and vacant lands 1.68 km2.
Industrial wastewater does not only flow into Citarum River but it flows further into drainage channels that pass through rice fields and housing areas.
Samples of water from 20 location points to asses Citarum water quality during a dry season indicated heavy contamination. The result of water quality test in river streams and dams during a dry season confirmed a heavy contamination in Citarik , downstream Cikeruh, upstream Cipamokolan, downstream Cipamokolan, Upstream Cikapundung, Middle Cikapundung, Cisangkuy, Saguling Dam outlet, Cirata Dam, downstream Ciasem, upstream Cipunagara, Middle Cipunagara, downstream Cipunagara. A test result confirming moderate contamination in river stream was found in water sample from Cibeet, Middle Ciasem, Situ Cisanti, Cirasea and upstream Cikeruh. While water samples from upstream Ciasem and Cikao river stream indicated light contamination.
Test results of Citarum water quality during a wet season showed an indication of moderate and light contamination. The water bodies whose sample confirming moderate pollution consist of Cirasea, Citarik, downstream Cikeruh, upstream Cipamokolan, upstream Cipamokolan, upstream Cikapundung, middle Cikapundung, Cisangkuy, Saguling Dam outlet, Cirata Dam, Cikao, Cibeet, downstream Ciasem, middle Ciasem, middle Cipunagara and downstream Cipunagara. While samples with a light pollution indication were from Situ Cisanti, upstream Cikeruh, upstream Ciasem and upstream Cipunagara.
Major flooding in Balleendah – Dayeuhkolot areas in December 2013.
Flooding was recorded to have occurred in 22 incidents between 2011 and 2013 in some areas in Bandung with water levels reaching 40 to 80 cm. Areas that have been frequently hit by floods throughout a rainy season every year are Dayeuhkolot, Baleendah and Bojongsoang with 6, 8 and 3 incidents respectively.
The worst impact of floods in the region was recorded on 13 February 2012 with 15,492 people affected and 345 others took refuge in Baleendah Sub-district, 13,783 affected and 215 took refuge in Dayeuhkolot Sub-district, 9,208 affected and 150 took refuge in Bojongsoang Sub-district.
Landslides were recorded to have occurred in 25 incidents in 2013, affecting various areas in West Java Province, including those located within Citarum River Basin namely the areas in Purwakarta, West Bandung and Cianjur Districts. Areas frequently hit by landslides in West Bandung District are Rongga, Parongpong, Gununghalu, Cililin, Cipongkor and Ngamprah Sub-districts. Sub-district areas prone to landslides in Cimahi City and Purwakarta District are Pasir Jambu (Cimahi City) and Bojong (Purwakarta District).