| Rawa Pening | |
|---|---|
 Rawa Pening in 2008 | |
  Rawa Pening | |
| Coordinates | 7°17′S110°26′E / 7.283°S 110.433°E /-7.283; 110.433 |
| Basin countries | Indonesia |
| Surface area | 2,500 to 2,670 hectares (25.0 to 26.7 km2; 9.7 to 10.3 sq mi) |
Rawa Pening (literally meaning 'Clear Swamp', from the JavaneseBening) is a lake in theAmbarawa Basin inCentral Java, Indonesia. It serves as a source of power, irrigation, and flood control, and is used for fishing. Due partly to the high numbers of aquatic plants, it may dry out by 2021.
Rawa Pening is located in the volcanicAmbarawa Basin inCentral Java,[1] betweenAmbarawa andSalatiga. It covers a total area of 2,500 to 2,670 hectares (25.0 to 26.7 km2; 9.7 to 10.3 sq mi).[2][3] It is shallow and swamplike,[1] with muddy banks.[4]
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.[5]
To protect Rawa Pening, the local government has enacted agreen belt policy. Several establishments, such as the tourist attractionKampoeng Rawa, were controversial owing to their construction within this belt.[6]
One of the major roles of Rawa Pening is as a source ofhydroelectricity, with a power station located on theTuntang River near the lake. Fishing is common as a source of supplementary income, and the water from the lake irrigates nearby rice fields. It has also been cited as being used forflood control.[4]
Numerous species of aquatic plants live in Rawa Pening, includingPanicum repens,[7]Eichhornia crassipes,Salvinia cucullata,[8] andHydrilla verticillata.[3] Estimates of the total number of species vary, from 20 in 1949 to 19 aquatic and 71 semi-aquatic species in 1972.[9] According to Soenarto Hardjosuwarno,P. repens is one of the main contributors to the formation offloating islands in the lake,[7] with M. Soerjani noting thatE. crassipes andS. cucullata also contribute.[8] The aquatic plants, such asH. verticillatta, take root in a large amount ofpeat (in some places measuring 2 metres (6.6 ft) thick), causing more peat to gather. Eventually, terrestrial plants take root in the floating islands as well.[10]
According to Tri Retnaningsih Soeprobowati, a researcher atDiponegoro University inSemarang, Rawa Pening could become dry by 2021 due to increasing sedimentation. She reports a total rate ofdeposition of 270 to 880 kilograms (600 to 1,940 lb) per day, averaging 780 tonnes yearly,[2] with the water level dropping 29% since 1989.[3] The overabundance of aquatic plants has been blamed, especiallyE. crassipes. As such, there are calls for a culling of theE. crassipes population to 20% by 2030.[3] Other suggestions include the introduction ofgrass carp to control the plant population and the use ofherbicides as last resorts.[2][3] The destruction ofH. verticillatta had earlier been attempted beginning in 1932, originally using mechanical methods but later switching to herbicides, These efforts were discontinued in the 1960s.[11]
