Rawa Pening (literally meaning 'Clear Swamp', from the Javanese ''Bening'') is a lake in the Ambarawa Basin in

Central Java Central Java ( id, Jawa Tengah) is a province of Indonesia, located in the middle of the island of Java. Its administrative capital is Semarang. It is bordered by West Java in the west, the Indian Ocean and the Special Region of Yogyakarta ...

, Indonesia. It serves as a source of power, irrigation, and flood control, and is used for fishing. Due partly to high numbers of aquatic plants, it may dry out by 2021.

Location and description

Rawa Pening is located in the volcanic Ambarawa Basin in

, between

Ambarawa Ambarawa is a town (and administratively, a district of the Semarang Regency) located between the city of Semarang and Salatiga in Central Java, Indonesia. Administratively, it is bordered by the districts of Banyubiru to the south, Jambu to th ...

and Salatiga. It covers a total area of . It is shallow and swamplike, with muddy banks.

History

Rawa Pening is estimated to have been formed between 18,000 and 13,500 BC after a period of increased precipitation. It reached its largest size from 11,000 to 9,000 BC, but shrank until it reached its current size around 6,000 BC. In order to protect Rawa Pening, the local government has enacted a

green belt A green belt is a policy and land-use zone designation used in land-use planning to retain areas of largely undeveloped, wilderness, wild, or agricultural landscape, land surrounding or neighboring urban areas. Similar concepts are greenway (lan ...

policy. Several establishments, such as the tourist attraction

Kampoeng Rawa Kampoeng Rawa ( jv, ꦏꦩ꧀ꦥꦸꦁꦫꦮ, Kampung Rawa) is a tourist attraction located within the green belt around Lake Rawa Pening of Ambarawa in Central Java, Indonesia. Opened in August 2012, it is owned and operated by twelve gr ...

, were controversial owing to their construction within this belt.

Role

One of the major roles of Rawa Pening is as a source of

hydroelectricity Hydroelectricity, or hydroelectric power, is electricity generated from hydropower (water power). Hydropower supplies one sixth of the world's electricity, almost 4500 TWh in 2020, which is more than all other renewable sources combined a ...

, with a power station located on the

Tuntang River The Tuntang ( id, Kali Tuntang) is a major river of northern Central Java, Indonesia, about 400 km east of the capital Jakarta.flood control Flood control methods are used to reduce or prevent the detrimental effects of flood waters."Flood Control", MSN Encarta, 2008 (see below: Further reading). Flood relief methods are used to reduce the effects of flood waters or high water level ...

Plant infestation

Numerous species of aquatic plants live in Rawa Pening, including ''

Panicum repens ''Panicum repens'' is a species of grass known by many common names, including torpedograss, creeping panic, panic rampant, couch panicum, wainaku grass, quack grass, dog-tooth grass, and bullet grass. Its exact native range is obscure. Sources ...

'', ''

Eichhornia crassipes ''Pontederia crassipes'' (formerly ''Eichhornia crassipes''), commonly known as common water hyacinth is an aquatic plant native to South America, naturalized throughout the world, and often invasive outside its native range.Salvinia cucullata ''Salvinia'', a genus in the family Salviniaceae, is a floating fern named in honor of Anton Maria Salvini, a 17th-century Italian scientist. Watermoss is a common name for ''Salvinia''. The genus was published in 1754 by Jean-François S� ...

'', and '' Hydrilla verticillata''. Estimates of the total number of species vary, from 20 in 1949 to 19 aquatic and 71 semi-aquatic species in 1972. According to Soenarto Hardjosuwarno, ''P. repens'' is one of the main contributors to the formation of

floating islands A floating island is a mass of floating aquatic plants, mud, and peat ranging in thickness from several centimeters to a few meters. Floating islands are a common natural phenomenon that are found in many parts of the world. They exist less co ...

in the lake, with M. Soerjani noting that ''E. crassipes'' and ''S. cucullata'' also contribute. The aquatic plants, such as ''H. verticillatta'', take root in the large amount of

peat Peat (), also known as turf (), is an accumulation of partially decayed vegetation or organic matter. It is unique to natural areas called peatlands, bogs, mires, moors, or muskegs. The peatland ecosystem covers and is the most efficien ...

(in some places measuring thick), causing more peat to gather. Eventually, terrestrial plants take root in the floating islands as well. According to Tri Soeprobowati, a researcher at Diponegoro University in

Semarang Semarang ( jv, ꦏꦸꦛꦯꦼꦩꦫꦁ , Pegon: سماراڠ) is the capital and largest city of Central Java province in Indonesia. It was a major port during the Dutch colonial era, and is still an important regional center and port today. ...

, Rawa Pening could become dry by 2021 due to increasing sedimentation. She reports a total rate of

deposition Deposition may refer to: * Deposition (law), taking testimony outside of court * Deposition (politics), the removal of a person of authority from political power * Deposition (university), a widespread initiation ritual for new students practiced ...

of per day, averaging 780 tonnes yearly, with the water level dropping 29% since 1989. The overabundance of aquatic plants has been blamed, especially ''E. crassipes''. As such, there are calls for a culling of the ''E. crassipes'' population to 20% by 2030. Other suggestions include the introduction of

grass carp The grass carp (''Ctenopharyngodon idella'') is a species of large herbivorous freshwater fish in the family Cyprinidae, native to the Pacific Far East, with a native range stretching from northern Vietnam to the Amur River on the Sino-Russi ...

to control the plant population and the use of herbicides as last resorts. The destruction of ''H. verticillatta'' had earlier been attempted beginning in 1932, originally using mechanical methods but later switching to herbicides. These efforts were discontinued in the 1960s.

References

;Footnotes ;Bibliography * * * * * * * {{Authority control Semarang Regency Rawa Pening Landforms of Central Java